INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
THE
INTERNATIONAL
HYDROGRAPHIC
REVIEW
INTERNATIONAL HYDROGRAPHIC BUREAU
MONACO
No. 9
MAY 2013
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□ Editorial
By Ian HALLS, Editor
5
□ Articles
- The Caris Engineering Analysis Module - Assisting in the
Management of Queensland’s Waterways.
7
by : Owen CANTRILL (Australia)
Daniel KRUIMEL (Australia)
- The GE.N.ESIS project - Georeferenced Depiction and
Synthesis of Marine Archaeological Survey Data in
Greece.
15
by : Panagiotis GKIONIS (Greece)
- Results of operational sea-wave monitoring with radar
gauges.
37
by : Sebastian RÜTTEN (Germany)
Stephan MAI (Germany)
Jens WILHELMI (Germany)
Theodor ZENZ (Germany)
Hartmut HEIN (Germany)
Ulrich BARJENBRUCH (Germany)
- Anomalous ECDIS Operations.
47
by : Dr Mohamed I. MOHASSEB (Egypt)
□ Notes
- A technical method on calculating the length of coastline
for comparison purposes.
53
by : Laurent LOUVART (France)
- New scientific contribution to the King Abdulaziz
University.
3
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Editorial
This edition comprises four Articles and two Notes.
The first Article outlines how Maritime Safety Queensland (MSQ) in Australia is using
state of the art CARIS software to assist in the management of their waterways. The
paper uses test results from surveys to identify improvements to volume calculations, survey conformance analysis, shoal detection and survey reference models.
The second Article describes the field work, processing and reporting for a new project
in Greece to assist with mapping, visualisation and synthesis of underwater archaeological data. The author describes the fieldwork procedures and the GIS capabilities used to
prepare the collected data in order to provide a potential model for the sustainable
management of Greek maritime archaeology. Ed. Note - as this model is developed, it is
hoped that S-100 may provide a suitable geodatabase model for managing such data
and information as discussed by Masetti, Calder and Alexander in the IHR November
2012 edition.
Our third Article discusses the development of a low cost, non-contact sea wave
monitoring system based on radar sensors. The results to date are promising in terms of
estimating wave heights and direction.
The final Article is a summary of issues relating to anomalies in ECDIS equipment in
terms of displaying recent changes to ENC data encoding and display standards
including complex symbology. These ongoing issues are not new, however the IHB has
been proactive in identifying the issues and raising awareness through several recent
Circular Letters. Using the IHB’s test data, the author runs the data through a couple of
ENC visualisation tools to determine the ability for them to display the symbols correctly.
Given that ECDIS has been operational for 20 years it is disappointing that interpretation
issues with S-52 display still exist. Hopefully, the work of the IHB in conjunction with the
IMO will soon rectify the issues. Ultimately, it is the responsibility of the type approval
agencies to ensure that ECDIS equipment conforms and perhaps there are more deep
seated issues regarding training and competencies in these areas. The maintenance of
software should not even be an issue today and manufacturers have the responsibility to
conform whilst users have the responsibility to understand the capability. “Buyer beware”
and “minimum performance specifications” are simply not acceptable with mandatory carriage requirements now in effect.
This Edition also includes two Notes :

The first Note describes the findings of an IHO Correspondence Group attempting to
harmonise the way in which IHO Member States define and measure the length of
their national coastlines.

The second Note provides a brief technical description of a new hydrographic survey
vessel for the King Abdulaziz University in Saudi Arabia.
On behalf of the Editorial Board, I hope that this edition is of interest to you. Thank you to
all the authors for your contributions and to my colleagues who provided peer reviews for
the Articles in this edition. My thanks also go to the IHB staff who finalise the publication
and provide translations.
Ian W. Halls
Editor
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THE CARIS ENGINEERING ANALYSIS MODULE
ASSISTING IN THE MANAGEMENT OF QUEENSLAND’S WATERWAYS
By Owen CANTRILL (Maritime Safety Queensland - Australia)
& Daniel KRUIMEL (Caris Asia Pacific - Australia)
Abstract
Maritime Safety Queensland (MSQ) is responsible for protecting Queensland's waterways
and the people who use them providing safer, cleaner seas. MSQ first incorporated CARIS
products into their workflow in 2009 with HIPS and SIPS and BASE Editor and in 2012 are
looking to utilize the new functionality of the Engineering Analysis module to assist them in
the management of their ports and waterways throughout Queensland. This paper will look
into how BASE Editor and the Engineering Analysis Module are being utilized in the Ports
and Waterways environment, with a focussed case study on the application with MSQ. Included in this will be a detailed comparison of techniques for volume computation (such as
end area volumes, hyperbolic and TIN volumes), a summary of the results that can be
achieved and the associated advantages/disadvantages with each method.
Résumé
La sécurité maritime du Queensland (MSQ) est chargée de la protection des voies
navigables du Queensland et des personnes qui les utilisent en leur procurant des eaux
plus sûres et plus propres. La MSQ a d’abord incorporé des produits CARIS dans son plan
de travail en 2009 avec HIPS et SIPS et BASE Editor et, en 2012, elle a cherché à utiliser
la nouvelle fonctionnalité du module d’analyse bathymétrique afin d’aider à la gestion de
ses ports et de ses voies navigables à travers le Queensland. Cet article examine la
manière dont BASE Editor et le module d’analyse bathymétrique sont utilisés à l’intérieur
des ports et des voies navigables avec une étude de cas consacrée aux applications à la
MSQ. Il comprend une comparaison détaillée des techniques de calculs de volumes (tels
que les volumes finis, les volumes hyperboliques et TIN), un résumé des résultats qui
peuvent être obtenus et des avantages/inconvénients de chaque méthode.
Resumen
La Autoridad de la Seguridad Marítima de Queensland (MSQ) es responsable de la
protección de las vías navegables de Queensland y de las personas que las utilizan,
proporcionando mares más seguros y más limpios. La MSQ incluyó los productos CARIS
por primera vez en su proceso de trabajo en el 2009, con HIPS y SIPS y el Editor BASE y
en el 2012 esperaban utilizar la nueva funcionalidad del Módulo de Análisis de Ingeniería,
como ayuda para la gestión de sus puertos y vías navegables en la totalidad del
Queensland. Este artículo profundizará sobre cómo el Editor BASE y el Módulo de Análisis
de Ingeniería están siendo utilizados en el entorno de los Puertos y las Vías Navegables,
con el estudio de un caso centrado en la aplicación de la MSQ. En dicho estudio se
incluirá una comparación detallada de técnicas para el cálculo de volumen (tales como los
volúmenes finales de áreas los volúmenes hiperbólicos y TIN) y un resumen de los
resultados que pueden obtenerse y las ventajas/desventajas asociadas a cada método.
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INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
INTRODUCTION
current functionality and utilize the new module to
assist them in the management of their ports and
Maritime Safety Queensland (MSQ) is a division of waterways throughout Queensland.
the Department of Transport and Main Roads within
the Queensland State Government. MSQ's role is to THE ENGINEERING ANALYSIS MODULE
protect Queensland's waterways and the people who
use them - providing safer and cleaner seas. Within The Engineering Analysis Module features under the
the corporate structure of MSQ, the Hydrographic 'Analysis' pillar of the Ping-to-Chart workflow, as part
Services section carries out hydrographic surveys on of the Bathy DataBASE suite of products. Recognisbehalf of clients. Current clients include North ing the fact that different users have different
Queensland Bulk Ports (Ports of Hay Point, Weipa, requirements, Bathy DataBASE is a scalable
Abbot Point and Mackay), Ports North (Cape Flat- solution.
tery, Thursday Island), Gladstone Ports Corporation
and Boating Infrastructure and Waterways Manage- In order to provide more functionality for users in the
ment (recreational boating facilities). These various ports and waterways environment, the Engineering
sites are spread over 1700Nm of coastline.
Analysis module was introduced to the Bathy
DataBASE product suite. The module works with
OVERVIEW OF OPERATIONS
either BASE Editor or BASE Manager, and includes
many functions migrated from an existing CARIS
MSQ utilize a variety of survey equipment, such as a application (BEAMS - Bathymetry and Engineering
Kongsberg Simrad EM 3002D multi-beam echo Management System).
These functions include
sounder, Klein 3000 Sidescan, Starfish 452f sides- volume computations, shoal management, conforcan, SEA Swath plus 234 kHz interferometry system, mance analysis and reference model creation and
Echotrak MK III dual frequenciy single beam, Deso maintenance.
300 single beam, Applanix POS MV 320, Applanix
CALCULATION
METHODS
FOR
POS MV Wavemasters and Lecia RTK DGPS. VOLUME
Surveys range from boat ramps that integrate land HYDROGRAPHIC SURVEYING
survey and a small hydrographic component,
through to high precision surveys for Under Keel The calculation of volumes in hydrographic surveyClearance systems.
ing is frequently used in dredging applications and
reservoir analysis (for example, sedimentation). A
A permanent installation of the EM3002D exists on number of different methods can be utilized in
the vessel QGNorfolk, with other mobile systems determining a volume. The 'best' method to use is
deployed on vessels of opportunity, such as the QG determined by factors such as the technique of
Bellara used during rapid response surveys in the sounding for the data (single beam, multi-beam,
2011 Brisbane floods.
LiDAR etc.) and also the nature of the material
(smooth, sandy bottom is quite different to an
MSQ ensures a high quality of work through the use undulating, rocky terrain).
of experienced and competent personnel. There are
six surveyors certified at Level 1 by the Australasian
"Accurate volume estimates are important for
Hydrographic
Surveyors
Certification
Panel
the choice of dredging plant, production
(AHSCP) and five surveyors (including graduates)
estimates and ultimately project costs."
that work under direct supervision.
(Sciortino J.A., 2011)
In an effort to improve acquisition to processing
ratios, MSQ first incorporated CARIS Ping-to-Chart
products into their workflow early in 2009, turning to
HIPS and SIPS for processing their bathymetric
data. Later that year, BASE Editor was also brought
on board to assist in bathymetric data compilation
and QC. Staff from MSQ have stayed well versed in
the latest functionality for the software packages
through participation in open training courses held in
the region by the CARIS Asia Pacific office. After
attending a training course on the new Engineering
Analysis Module (compatible with BASE Editor) in
August of 2011, MSQ sought to expand on their
8
In addition to the volume of material, the type of
material is another important factor. The cost of
dredging rock will be much higher compared to the
same amount of material in sand.
End Area Volumes
End Area volumes have been derived from
land-based methods used in railroad and roadway
construction. They involve calculating the volume
from cross sections of a channel, surveyed at regular
intervals (see Figure 1).
INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
The key components in computing the volume are
the cross sectional area (an average is taken of the
two areas) and the length between the cross
sections. This method assumes that the cross
sectional area is relatively constant between two
successive cross sections. If this assumption is not
true, the volume produced will realistically just be an
approximation.
Hyperbolic Volumes
For this method, a hyperbolic cell is created from the
centres of every four adjacent grid cells. The depths
from the grid cells are used as the depths for the
corners of the hyperbolic cell. For this calculation,
the surface is modelled as a collection of hyperbolic
paraboloid sections, with a hyperbolic paraboloid
created to smoothly pass through the points of each
hyperbolic cell (see Figure 2). This gives a smooth
approximation of the surface and good volume
results, but is processing intensive and can be time
consuming.
Rectangular Volumes
In this method, a single depth value from each cell
(or bin) in the surface is used to calculate the
volume. The surface is modelled as a collection of
disjointed rectangular prisms, with the depth for each
Figure 1: Calculation of End Area Volumes (USACE, 2001).
grid cell becoming the depth of the prism (see
Figure 3). In comparison to the previous hyperbolic
TIN Volumes
method, this results in a much more 'simple' volume
calculation which is processed much faster, however
Triangulated Irregular Network (TIN) Volumes are the accuracy of the computed volume may not be as
based on the true positions of depths to calculate the reliable.
volume of a surface. This calculation involves
modelling the surface as a collection of small planes. One limitation on the rectangular volume method is
TIN's can either be derived from a gridded bathym- the inability to perform a volume calculation against
etry source (i.e. surface) or from a point cloud. One a sloped or non-horizontal surface in a reference
advantage in using the TIN method (particularly for model (for example the bank of a channel). This is
point data) is that the true position of the source because by definition, a rectangular prism cannot
depths will be utilized in the volume calculation. This have a sloped edge, so only horizontal reference
is the historically preferred method for most dredging surfaces are supported.
type applications where volume is critical.
Figure 2: Representation of the hyperbolic paraboloid
volume method
Figure 3: Representation of the rectangular volume
method
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INTERNATIONAL HYDROGRAPHIC REVIEW
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VOLUME COMPARISONS
As previously outlined, there are a number of
different methods available to the hydrographer for
volume determination. So this leads to the next
question - which method should be used? This will
largely be dependent on what technology is available
to conduct the survey. If the user only has access to
a single beam echo sounder, they will be limited to
end area volumes and TIN volumes. For a full density multibeam survey, rectangular and hyperbolic
volumes can also be taken into consideration.
The nature of the seafloor (or riverbed/reservoir)
could be another factor in determining which is the
most suitable volume method to be used. If the
bottom topography is smooth (such as with sand),
hyperbolic volumes, which produce a smooth
estimate of the terrain using constructed hyperbolic
paraboloids could yield the best results. For a
harsher, rocky terrain, TIN volumes utilizing the true
positions of each depth may be the most robust
answer.
be removed to bring the channel down to a declared
depth of 16m (Note: this is just an arbitrary value
chosen for testing purposes). The methods used for
comparison were hyperbolic, rectangular and TIN
volumes. Simulated end area volumes were also
calculated by extracting profiles from the multi-beam
bathymetry at intervals of 25m, 50m and 100m. The
results can be seen in Table 1. (Note: In this case,
the hyperbolic volume has been used as the benchmark for determining volume difference and error for
other methods. This does not mean that there is
zero error in the hyperbolic volume result).
The results displayed in Table 1 yield some interesting results. As could be expected, the two volumes
closest to each other are the hyperbolic and TIN
volumes. What is probably most surprising are the
results achieved through the use of end area
volumes. One would generally assume that profile
spacing would be inversely proportional to the
volume difference/error (i.e. the lesser distance
between profiles, the greater the accuracy of the
computed volume). This is not reflected in these
results, where the error actually decreases as the
interval increases.
Table 1: Comparison of volume results for the test area in Weipa
METHOD
VOLUME (m³)
DIFFERENCE (m³)
VOLUME ERROR (%)
Hyperbolic Volume
794,912.5
0
0
Rectangular Volume
805,090.2
10,177.7
1.280
TIN Volume
798,654.4
3,741.9
0.471
803,019.1
8,106.5
1.020
802,755.3
7,842.7
0.987
802,022.8
7,110.2
0.894
End Area (25m
Interval)
End Area (50m
Interval)
End Area (100m
Interval)
Case Study in Weipa
This may be due to the nature of the seabed. The
data used was a pre dredge data set following the
wet season. The channel is typically smooth and
shaped in a reasonably consistent V shape due to
the amount of siltation and the effect of significant
shipping movements which assist in keeping the
centreline clear of siltation.
In order to test the results produced by the various
methods of volume calculation, a case study was
carried out using survey data collected by MSQ at
the Port of Weipa in October, 2011. The data was
provided as an ASCII XYZ file that had already been
binned at 1m. A reference model for the Port of
Weipa was also used in the calculations. The test Validation of Case Study
area used is a section of channel located just to the
east of beacons 7 and 8 in the south channel.
As the results produced in the Weipa case study did
not reflect expected results, an additional independVolumes were calculated in the test area to ent case study was sought out. One was found by
determine the amount of material that would need to Dunbar J.A and Estep H of the Baylor University
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INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
Department of Geology (BU) in Texas, USA. The
project undertaken by BU was to study the hydrographic surveying methods utilized by the Texas
Water Development Board (TWDB) in determining
water and sediment volume in reservoirs throughout
Texas. Whilst the project also investigated sub
bottom profiling and sediment surveys, the volume
comparison was carried out in Lake Lyndon Baines
Johnson (LBJ), a Highland Lake on the Texas
Colorado River.
The results produced in the study by BU can be
seen in Table 2. They are also shown graphically in
Figure 4. When extracting the profile sets to
produce simulated volumes, BU did this in two runs
(Run 1 and Run 2). This meant that for each
simulated profile spacing, two independent sets of
profiles were extracted from the multi-beam bathymetry.
By undertaking a statistical analysis of the BU
Volume comparison results, values from Run 1 have
As part of the project, Hydrographic Consultants Inc a coefficient of correlation of 0.884 and 0.936 for
collected and processed a multi-beam survey in Run 2. This indicates a strong positive correlation
Lake LBJ. In order to evaluate the influence of between profile spacing and volume error, which is
survey profile spacing on volume accuracy:
what we would generally expect. However despite
the strong correlation, there are inconsistencies in
"BU extracted simulated profiles at spacing’s
the data. Such as the very low value of 0.14 % for
ranging from 100 to 2000 ft from a high1000 ft profile spacing in Run 1, and a difference of
density multi-beam survey collected by an
0.696% in Run 1 and Run 2 error for 300 ft profile
independent contractor. Volume calculations
spacing. This is because the Volume Error of
based on the extracted profile sets were
0.718% for 300 ft profile spacing in Run 1 is higher
compared to the volume based on the full
than expected in contrast to other results.
multi-beam survey. " (Dunbar, J.A, Estep, H,
2009)
Table 2: Results of BU Volume Comparisons (Dunbar, J.A, Estep, H, 2009)
Figure 4: Scatter plot and 3D line graph of BU volumes comparisons.
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INTERNATIONAL HYDROGRAPHIC REVIEW
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From these results, a conclusion can be drawn that
when increasing the population size of our sample
dataset, the error values do display a tendency for
strong positive correlation. In the Weipa Case
Study, the population size was only three (25m, 50m
and 100m spacing) so these results were not
apparent.
If further intervals were added and
multiple runs (as in the BU example), perhaps we
could expect to see similar results.
management and the creation, editing and maintenance of reference models. When computing volumes, users should consider what type of volume
will deliver the most accurate results. While End
Area volumes have traditionally been widely used,
this paper presents evidence that TIN volumes and
hyperbolic volumes should be taken into consideration as they are capable of producing volume results
that are reliable and repeatable.
It could therefore be argued that while there is a
trend for volume error to increase with profile
spacing, for any given dataset based on one set of
profiles (i.e. a single beam survey) the accuracy of
the volume is essentially down to 'luck.' In their
report, Dunbar J.A and Estep H state that "Reducing
the profile spacing to less than 500 ft does not guarantee improved volume accuracy. " (Dunbar, J.A,
Estep, H, 2009)
The Engineering Analysis Module has provided MSQ
with the ability to compute volumes faster and on
much larger data sets than their existing capability,
along with new functionality for advanced visualization techniques. The ability to increase the data sets
reduces the trade off historically required between
precise volumes (e.g. 0.5m spaced data) with practical processing limits. (Data generalised to 2.5m)
REFERENCES
VOLUME COMPUTATIONS AT MSQ
MSQ have traditionally used the TIN method to
compute volumes for their hydrographic surveys. As
part of an evaluation for the Engineering Analysis
Module in 2011, MSQ ran a comparison of TIN
volume computations using the module against their
existing capability. Results from the comparison can
be seen in Table 3. The Engineering Analysis
Module produced the same TIN volume results, in
less time across all cases, as well as having the
ability to compute a volume for the entire channel
(which the existing capability was not able to
achieve).
Cantrill, O, (2012) General Aspects of Port Surveying and Shallow Water Bathymetry, Proceedings of
SWPHC Ports & Shallow Water Bathymetry Technical Workshop, Brisbane, Australia, March 13-14.
Dunbar, J.A, Estep, H, (2009) Hydrographic Survey
Program Assessment Contract No 0704800734,
Baylor University Department of Geology, Waco, TX.
Kruimel, D, Fellinger, C, (2011) Bathymetric Data
Management: The Ports and Waterways Environment, Proceedings of Hydro 2011 Conference, Fremantle, Australia. November 7-10.
Table 3: Volume results and processing times at MSQ
CARIS Engineering Analysis Module
Time to Process
Existing capability
(hh:mm:ss)
Volume to
Dredge (m³)
Whole Channel
0:47:00
116,724
Not enough memory to compute
BN16 - BN18
0:01:57
2,234
0:03:14
2,233.8
BN6 - BN 8
0:05:50
31,015
0:19:34
31,016.2
BN 8 - CH15500
0:02:00
19,049
0:02:45
19,048.8
BN2 - BN4
0:05:52
10,492
> 1 hr
9867
Area
CONCLUSION
The Engineering
assist users in
through the use
cated volume
Time to Process
(hh:mm:ss)
Volume to
Dredge (m³)
Not enough
memory to compute
Sciortino, J.A, (2011) Fishing Harbour Planning,
Construction And Management: FAO Fisheries And
Analysis Module is able to greatly Aquaculture Technical Paper No. 539
managing Ports and Waterways
of conformance analysis, sophisti- USACE, (2001) Hydrographic Surveying, Engineercomputations, shoal detection/ ing Manual 1110-2-1003, United States Army Corps
of Engineers, Washington, DC.
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INTERNATIONAL HYDROGRAPHIC REVIEW
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BIOGRAPHIES
Owen Cantrill is a Level 1 Certified Hydrographic
Surveyor having gained certification in 2000. He
gained a Bachelor of Surveying with honours from
the University of Melbourne in 1989. He is currently
employed as the manager of the Hydrographic
Services section of Maritime Safety Queensland
(MSQ). [email protected]
Daniel Kruimel is an active member of the Spatial
Industry and is currently a member on the SSSI
Regional Committee of South Australia, as well as
the Hydrography Commission National Committee.
At the start of 2011, Daniel took up a role with
CARIS Asia Pacific as a Technical Solutions
Provider. [email protected]
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THE GE.N.ESIS PROJECT
Georeferenced Depiction and Synthesis of Marine
Archaeological Survey Data in Greece
By Panagiotis GKIONIS
(Hellenic Navy Hydrographic Service with Plymouth University - UK)
Abstract
Through the GE.N.ESIS project, the Hellenic Ephorate of Underwater Antiquities (EUA) is
introduced to a digital tool for visualisation and synthesis of underwater archaeological
data. A marine geoarchaeological survey was conducted at the Methoni underwater
archaeological site (Greece) in the summer of 2012 utilising geophysical instruments. The
acquired data together with archival archaeological data was managed through a
Geographical Information System (GIS). The survey results present the ruins of a
submerged prehistoric settlement, the Methoni ancient harbour and submerged
breakwater, wrecks, cannons and artefacts/features – all of which are of potential
archaeological interest. The project outcomes provide the genesis of a new baseline
capability for the cultural management of the Greek archaeological sites.
Résumé
Dans le cadre du projet GE.N.ESIS, l’éphorat grec des antiquités sous-marines (EUA) est
présenté via un outil numérique de visualisation et de synthèse des données archéologiques sous-marines. Un levé géo-archéologique marin a été réalisé sur le site d’archéologie marine de Méthone (Grèce) au cours de l’été 2012 à l’aide d’instruments de
géophysique. Les données acquises ainsi que les données archéologiques d’archives ont
été gérées via un système d’information géographique (SIG). Les résultats du levé
présentent les ruines d’une zone de peuplement préhistorique submergée, l’ancien port
de Méthone et des brise-lames, épaves, canons et artefacts/éléments submergés – tous
d’intérêt archéologique potentiel. Les résultats du projet fournissent la génèse d’une
nouvelle capacité de base pour la gestion culturelle des sites archéologiques grecs.
Resumen
Gracias al Proyecto GE.N.ESIS, le ha sido presentada al “Hellenic Ephorate of
Underwater Antiquities” (EUA) una herramienta digital para la visualización y la síntesis
de datos arqueológicos submarinos. Un levantamiento geoarqueológico marino fue
efectuado en el sitio arqueológico submarino de Methoni (Grecia) durante el verano del
2012, utilizando instrumentos geofísicos. Los datos adquiridos, junto con los datos de los
archivos arqueológicos, fueron administrados a través del Sistema de Información
Geográfica (SIG). Los resultados del levantamiento presentan las ruinas de un emplazamiento prehistórico sumergido, el antiguo Puerto de Methoni y el rompeolas sumergido,
restos de naufragios, cañones y artefactos/objetos, todos ellos de un interés arqueológico potencial. El resultado del proyecto proporciona la génesis de una nueva capacidad de
referencia para la gestión cultural de los sitios arqueológicos griegos.
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INTRODUCTION
Methoni is a Greek seaside town at the southwestern extremity of the Messenia Peninsula (Fig.1),
also known as Pylia Region. There is archaeological
evidence supporting that the human presence in the
area which nowadays forms the Methoni Bay, dates
back to the Bronze Age (Spondylis, 1996).
Figure 1. Pylia Region in Greece and the Methoni Bay
(ESRI, 2012)
In the historical periods that followed, the vigorous
activities of the local population and the naval battles
fought off Methoni were prominent themes through
the literature. The harbour of Methoni was strategically significant (Biris, 2002) and this is evident from
the successive improvements of the initial fortification of the ancient town which took place following
the second Messenian War and the town’s independence around 369 B.C. Methoni’s strategic role
through the centuries is evident from the repeated
predatory raids/expeditions of Romans, Venetians,
Turks and the French in the area from the 12th to the
19th century. Its importance is mainly evident through
the existence of its harbour dating from the Archaic
Period of Ancient Greece according to Homer’s Iliad
(UoA, 2012) and the successive improvement works
on the harbour’s breakwater (Lianos, 1987) by some
of the above mentioned expeditionary forces. Although in the 18th century the capacity of the harbour
was enough to accommodate 7 or 8 galleys (Lianos,
1987), nowadays its breakwater is submerged lying
just below the sea surface and the harbour has not
been used commercially since a new breakwater
was constructed in the 19th century closing its entrance (Fig. 2 and 3).
Figure 2. The town of Methoni, the
fortification of the ancient town, the
ancient submerged breakwater and
the latest breakwater which closes
the entrance of the ancient harbour.
Figure 3. The 19th century breakwater over the (nowadays
merged) ancient breakwater.
sub-
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Since 1993, the archaeological surveys and excavations undertaken by the Hellenic Ministry of Culture /
Ephorate of Underwater Antiquities (EUA) confirmed
the glorious historical past of Methoni, bringing to
light numerous antiquities at the site. Prehistoric
settlement ruins have been discovered lying on the
seabed at a depth of 3.5-5m (Fig. 4). Together with
parts of a medieval coastal stone fresh-water
pipeline, they have been documented with the use of
land survey methods. A number of wrecks, pottery, a
prehistoric stone anchor (Fig. 5) and other antiquities have also been discovered in the same area
revealing the maritime roots of the local population
through the millennia (Spondylis, 2000).
Previous to the summer of 2012 and from pure
archaeological surveys, no marine geophysical survey had ever been conducted off Methoni. All
governmental survey records concerning Methoni
and other underwater sites were archived in either
paper form or simple electronic means in no specific
format (Spondylis, 2011). Hence, the Greek government archaeologists could only make archival site
investigations from distinctive sources of conventional data (maps / architectonic plans) with very few
options of further data correlation spatially
referenced. Further, it was difficult to analyse survey
data provided by external partners in sophisticated
formats, mainly because of format incompatibility
with existing EUA IT suites or inefficiency in spatial
correlation of existing data with the data provided.
Figure 4. Ruins of a square
building at the prehistoric
submerged town of Methoni.
Figure 5. Prehistoric stone
anchor, discovered at Methoni
Bay in 2000.
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The GE.N.ESIS Project (GEoreferenced depictioN
and synthESIS of marine archaeological survey data
in Greece) introduced the Ephorate of Underwater
Antiquities (EUA) to a digital management tool for
visualisation, synthesis and analysis of underwater
archaeological data. Within the objectives of the project were (a) the conduct of a marine geophysical
survey of the ruins of the prehistoric submerged
town of Methoni, the submerged breakwater of the
town’s ancient harbour and potentially of other local
underwater antiquities and (b) the visualisation, georeference, synthesis, analysis and management of
existing archival archaeological data and survey data
acquired during the survey using a GIS.
GIS in Maritime Archaeology
GIS have growing applications in maritime archaeology (Green, 2004). They allow the display, synthesis and analysis of archaeological and relevant data
in geographical space and in such a form that spatial
and/or chronological trends of a site can be visualised (NAS, 2009). Layering of ortho-images and
datasets from sonar traces or archaeological records
is a typical GIS application. A fieldwork oriented GIS
can be interfaced with geophysical and positioning
systems, to allow survey planning, the provision of
real-time positioning information during data acquisition phase and pure archaeological data recording
(3H Consulting, 2012). Moreover, GIS facilitates the
determination of legal aspects during surveys
through the monitoring of archaeological site boundary delimitation. Most significantly, GIS can be used
as a data manipulation tool for digital storage and
database creation as well as a decision support tool
for site and holistic cultural heritage management.
The EUA has neither implemented an office-based
nor a real-time data monitoring/collection GIS, so
even when EUA survey partners use one for data
acquisition, the post visualisation and analysis of
data is inadequate or non-existent.
The information presented in the following sections
includes a brief background of the EUA’s underwater
geo-archaeological surveys and site management,
the methodology implemented for the survey, the
survey and the project results, leading to the
recorded features of potential archaeological interest
and a spatial synthesis and depiction of results
through a GIS. Discussed will be issues of further
scientific concern which qualify and quantify the data
reliability and support the interpretation of results.
Finally, conclusions and recommendations for further
research and project development will be addressed.
Legislation – Legal Issues
Further information about the project can be found
on the web at www.methoni-genesis.blogspot.com.
The Nautical Archaeology Society (2009) provides a
good guide for a study on International Law concerning underwater archaeological surveys. Greek LegisBACKGROUND
lation is applied according to the Greek Law No
Underwater Archaeology and Marine Geophysi3028/2002 (‘’On the Protection of Antiquities and
cal Surveys in Greece off Methoni
Cultural Heritage in general’’) and relevant GovernThe EUA is the governmental agency for marine ar- mental Directives for licensing issues. The participachaeology in Greece. It was founded in 1976 and tion of the EUA in all maritime archaeological surtogether with the Hellenic Institute of Marine Archae- veys off the Greek coasts and literally the direction of
ology are the only bodies that systematically conduct all surveys by the EUA are legal prerequisites. Ilias
pure marine archaeological surveys in Greece. How- Spondylis was assigned by the EUA as the Survey
ever, in the light of the particularities of underwater Director Archaeologist.
archaeological investigations, the need for integrated
scientific collaboration during surveys was early METHODS
identified and Spondylis (1996) had early addressed
Preparatory Tasks
the need for multi-scientific research to be conducted
off the southwest coasts of Greece.
Locating resources for the project was a major factor
for the best possible project outcome. Staffing the
Since 1976, the EUA in collaboration with other project adhered to the general rules of Green (2004).
research Institutes, industrial partners and universi- Apart from the author, the participation of Gwyn
ties, has undertaken numerous surveys sponsored Jones (Plymouth University, MSc Hydrography
by the survey collaborators off the Greek coasts programme Leader) as Project Supervisor and Konwhere remote sensing techniques and often state-of- stantinia Tranaka, a professional administrator and
the-art geophysical instruments were utilised. nurse, provided enhanced expertise for handling
Despite ongoing discussion amongst geologists and sophisticated geophysical hardware/software and
archaeologists about the reasons that led the prehis- dealing with Health and Safety issues. The EUA
toric town of Methoni being submerged (Spondylis, granted the provision of the Director Archaeologist,
1996), until this project, no geophysical survey had divers and a coxswain for the survey boats.
been conducted off Methoni.
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Aris Paleokrassas contributed to the project as a
marine surveyor. Financial resources were secured
by the Plymouth University funding scheme and the
author’s personal budget.
All assets used are presented in the next sections.
A preliminary site reconnaissance took place in
Methoni in early April 2012 for familiarisation with the
site, to undertake coastlining and for definition of
minimum depth inside the ancient harbour ensuring
the safety of boat operations. Since the ancient
harbour is now enclosed, a passage had to be
located over the submerged breakwater crest
(Fig. 6) so that the survey boat could enter the
harbour with a safe clearance depth under its keel.
Figure 7. Laboratory tests.
Figure 6. Preliminary underwater reconnaissance of the
harbour’s breakwaters. A measuring pole was used for detection
of a point of maximum depth over the submerged breakwater
and the definition of minimum depth inside the ancient harbour.
Laboratory tests (Fig. 7) were conducted during
early June 2012 to familiarise the operator with the
survey equipment and software and to investigate
methods for very-shallow-water towfish deployment.
Sea trials were conducted in Plymouth Sound during
June 2012. The aim was to simulate the imminent
survey tasks expected at the site, so that problems
related to the actual survey and its specifics could be
identified at an early stage. The objectives of the sea
trials were to set up the survey instruments for sea
(Fig. 8), to test very-shallow-water deployment
techniques of sidescan sonar and magnetometer
towfishes (Fig. 9, 10) and to evaluate acquired data
samples for definition of the optimum towing technique. Towing the towfishes by the stern with a float Figure 8. Magnetometer setup afloat.
rigidly attached on top of them proved to be the optimum deployment method (Fig. 10a) at that stage.
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Figure 9. Investigation of optimum ultra shallow water deployment technique for towfishes : Testing the
attachment of a towfish on a custom-built catamaran at Plymouth Sound.
Figure 10. Investigation of optimum ultra shallow water deployment technique for sidescan towfish.
Left (a): A float rigidly attached to the towfish.
Right (b): A float attached to the towfish cable.
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System checks were conducted prior to mobilisation
overseas to verify good operational condition and
integration of all survey instruments. The Hemisphere Crescent VS110 GPS was initially chosen for
positioning. It utilises EGNOS differential corrections
and according to ESSP (2012a), the expected
horizontal accuracy over the Methoni site area
should be in the order of 3m (95% of the time).
However, during the system checks it became
apparent that Open Service differential corrections
were not available for prolonged periods due to
Signal-In-Space (SIS) outage for both EGNOS PRNs
(120, 126). The history of SIS outages highlighted a
recent period of significant signal instability (ESSP,
2012b). In the light of this fact, the use of the C-Nav
2050G DGNSS was decided. After software updates
for the C-Navigator I unit and firmware updates for
the receiver unit, the reception of RTG (C1)
corrections marked the end of system checks.
All the surveying equipment was mobilised early July
2012 across Europe by car. The project team settled
in a Ministry of Culture guesthouse at the Pylos
fortress 10km away from Methoni.
Reconnaissance
During the period between the team settling in and
the start of the fieldwork, reconnaissance took place
in Methoni ashore, underwater and afloat. Although it
was conducted in a rather informal way, the team
discovered a cannon (Fig. 11a) probably linked to a
wreck which was simultaneously discovered nearby
(Fig. 12). Another cannon had been discovered by a
local resident in the same area a few days previous
(Fig. 11b).
Figure 11. Cannons on the seabed of Methoni Bay.
Left (a): The cannon that was discovered by the team.
Right (b): The cannon that was discovered a few days before the start of fieldwork.
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Fieldwork
The fieldwork took 7 days between the 11th and 27th
of July 2012. Sidescan sonar, magnetometer and
sub-bottom profiler were used for the survey, providing a wide range of remote sensing techniques to be
implemented for the underwater investigation of the
site and the potential of data correlation for artefact
identification. The first phase of the fieldwork
(sidescan sonar and magnetometer survey) was
conducted utilising a 5.50m RHIB provided by EUA.
For the second phase (seismic survey) the EUA
mobilised a 6.85m RHIB from Athens to Methoni.
Four areas off Methoni (Fig. 13) were identified to be
surveyed: (a) area ‘A’ for the visualisation of the
submerged prehistoric settlement ruins and its
sub-seabed profile, the estimation of its potential
extent under and over the seabed and for artefact
detection and identification (b) area ‘B’ for the
visualisation of the submerged ancient harbour and
breakwater as well as for artefact detection and
identification (c) area ‘C’ due to the recent findings
on the seabed (a wreck and two cannons), for
artefact detection/identification both on and under
the seabed and (d) area ‘D’ for artefact detection
only under the seabed due to low equipment availability at the final stage of the project.
Figure 12. Cannonballs on top of the ballast load of a wreck.
Figure 13. The four survey areas off Methoni.
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For data acquisition, processing and rendering, the
following geodetic parameters were used: For
Horizontal control, UTM Grid/Projection (34N,
18-24E zone) and ITRF2005 Datum (ITRF2005
coordinates coincide with WGS84 coordinates at the
decimetre level (ITRF, 2012)). Vertical control was
not applied since no bathymetric survey was
conducted and the maximum tidal range for the
nearby Kalamata port is 0.58m (HNHS, 1991). The
observed tidal range during the survey period never
exceeded 0.15m (IOC, 2012).
Correction Service for the project through Plymouth
Univesity, hence distribution of satellite based
differential GNSS corrections with no additional
equipment required (reference/base stations).
The C-Nav Correction Service has 99% availability
and EGNOS Open Service corrections can also be
accessed. The C-Navigator I Control and Display
unit was used as a quality control tool for monitoring
performance, data quality and accuracy of the
receiver.
For positioning information the C-Nav® Precise Point
Positioning (PPP) System was chosen (sourced by
Plymouth University). It is a dynamic DGNSS which
provides worldwide positioning of decimetre level
accuracy (C&C Technologies, 2012). Its 2050G
receiver integrates a 24-channel, dual frequency
GPS receiver, a 2-channel Satellite Based Augmentation System (SBAS) receiver and a C-Nav Correction Service L-Band receiver. The raw data latency is
less than 20ms and the receiver outputs up to 5Hz
raw measurement data in the standard configuration.
The GeoAcoustics SS941 dual frequency Sidescan
Sonar Transceiver combined with the Model 159D
dual channel towfish were sourced by Plymouth
University and used for artefact detection and
seabed feature mapping. The SS941 Transceiver
operated at 410 KHz was triggered externally and
the operational parameters were controlled remotely
by the Coda DA1000 acquisition system. The
acquisition range was 32-38m. The 159D towfish
was initially deployed by the stern of the RHIB having a float attached to it, but soon a noisy data acquisition became apparent and the towfish was deThe C-Nav world DNGSS division of C&C Technolo- ployed from the bow (Fig. 14) resulting in improved
gies, Inc. provided free worldwide access to the C1 data acquisition.
Figure 14. The GeoAcoustics sidescan sonar towfish deployed by the bow of the survey boat.
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The Geometrics G-882 Cesium magnetometer,
provided by Plymouth University, was utilised for
artefact magnetic detection (Fig. 15). Being small
and lightweight, it provided flexibility for the RHIB
survey operations. The G-882 performs at an absolute accuracy of better than 3nT throughout range
and its typical operating sensitivity for the actual
survey sample rate (10Hz) is better than 0.002 nT
P-P (Geometrics, 2012). The towfish was deployed
by the RHIB stern having attached a float on top of it.
During and after the magnetometer survey, all
vessels anchored in the area were positioned so as
their magnetic anomalies could be identified and
excluded from the dataset during post-process.
For the seismic survey, the GeoAcoustics GeoPulse
Pinger was provided by Akti Engineering. It is a
flexible sub-bottom profiler (SBP) allowing operation
as an ‘over-the-side mount’ system onboard small
boats (Fig. 16). The system utilises the Model 5430A
Transmitter (which controls the output power,
frequency and transmit repetition rate), the Model
5210A Receiver and the over-the-side Transducer
Mount Model 132B which houses a four transducers
array. The SBP was operated at a 3.5 kHz central
frequency and at a variable output power according
to the depth and sub-seabed structure. Areas ‘A’, ‘C’
and ‘D’ were investigated by the SBP.
Figure 15. The Geometrics
G-882 magnetometer.
System checks of
the
GeoAcoustics
GeoPulse
Pinger.
Figure 16.
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For magnetometer data acquisition, processing and
helmsman’s guidance along navigation lines, the
Site Searcher software was used, provided by 3H
Consulting Ltd. The HYPACK® MAX software was
used for navigation planning, helmsman’s guidance
and recording control during the seismic survey,
sourced by Akti Engineering. Geodetic transformation parameters of both systems were found to be
coincident maintaining seamless datasets. For
sidescan sonar data acquisition, processing and
SBP data processing, the Coda DA1000 hardware
and the Coda GeoSurvey software were used, both
sourced by Plymouth University. The SonarWiz Map
suite, sourced by Akti Engineering, was used for
seismic data acquisition integrated with the
HYPACK® MAX Software.
Following the geophysical survey, a precise positioning task was conducted. Two wrecks, two cannons
and various artefacts were precisely positioned. For
this task, a diver had to attach a float to one edge of
a line and hold the other edge on top of the point to
be recorded while keeping the line under tension to
achieve verticality. Simultaneously, a snorkeler had
to attach the C-Nav antenna on top of the float and
keep it there until the position was recorded
(Fig. 17).
Post-survey Tasks
The survey team returned to the UK either by road or
air transportation. The survey instrumentation was
demobilised largely by freight service provided by
Teletrans SA without charge and partly by private
car / road. After returning back to the UK, the GEoreferenced depictioN and synthESIS (GE.N.ESIS) of
marine archaeological survey data was conducted
utilising the Site Recorder (SR) software sourced by
3H Consulting Ltd. SR is a GIS suite used for
integration of information either recorded during an
archaeological survey or post synthesised. It
combines mapping, finds database, survey
processing program, dive log and image management tools (3H Consulting, 2012).
Figure 17. Precise positioning of a wreck.
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RESULTS
Magnetometer Survey
Sidescan Sonar Survey
Table 1 (see p. 25-27) presents a selection of
detected small scale features of potential archaeological interest through sonograph imagery. Feature
dimensions are given as horizontal by vertical length
and numbering retains the originally logged values.
Mosaics of acoustical seabed imagery of survey
areas and imagery of large scale features are
presented through the synthesis of archaeological
data in the following paragraph. The sidescan sonar
data post-process procedure included manual
sea-bed tracking corrections, navigation editing, and
Time Variable Gain adjustments.
Following the 1st-stage magnetometer data postprocessing (normalisation and filtering), magnetic
anomaly plots were mapped using the GIS. Fig. 18
and 19 present the magnetic anomaly plots in the
vicinity of the submerged settlement (area ‘A’) and
the ancient harbour (area ‘B’) on a different
basemap. Strongest anomalies are referred to
deeper red and green data samples/points.
Figure 18. Magnetic plot of area ’A’ after 1st stage data post-process (SR screen dump).
Figure 19. An introduction to data synthesis: Magnetic plot of area ’B’ (the ancient harbour and
the submerged breakwater) on a Google Earth basemap (SR screen dump).
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Table1. Selection of detected small scale sidescan sonar features.
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Table1. Selection of detected small scale sidescan sonar features.
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Table1. Selection of detected small scale sidescan sonar features (continuation).
During the 2nd-stage data post-processing, the
magnetic profiles of survey areas were created after
further normalisation of data by filtering excessive
yaw effect, instrument noise and turning points
(Fig. 20, 21). Subsequently, wherever necessary,
magnetic anomaly maps of the above mentioned
areas were created following a 3rd-stage data postprocess, namely parasite/contamination removal
(Fig. 22). In the following maps, all magnetic anomaly map projections are perspective and Grid North
coincides with y (Northings) axis. The Krigging data
interpolation method was used for the magnetic
model creation.
Figure 21. Magnetic profile of survey area ‘A’ after 2nd-stage
data process. The two large spikes correspond to anomalies
caused by the keels of sailing vessels at anchor.
20. Magnetic profile of survey area ‘C’ after 2nd-stage
data process. The large spikes at the northeast extremity of the
area were caused by cannons, wreck artefacts and unknown
features. Unknown features also caused the spikes at the northwest extremity of the area.
Figure
29
Figure 22. Magnetic profile of survey area ‘A’ after 3rd-stage
data process. Among others, the two spikes caused by vessels
at anchor are filtered.
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In the following list of SBP features (Table 2), extended profiling sections were not possible to be atIn this section, selected subsea-bed features
tached. All sections run from West (left) to East
detected during the survey and deemed to be of
(right) and depth values are below sea surface.
potential archaeological interest, are presented. For
the SBP data post process, sub-bottom sections
around potential targets were created after sea-bed
tracking and applying a separate set of 3zone (water column zone, seabed zone and
sub-seabed zone) time varying frequency filters to
Table 2.
Selection of detected small
the data for each section.
scale SBP features.
Seismic Survey
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Synthesis of Marine Archaeological Data
In this section, selected data elements of the synthesised digital GIS project are presented, highlighting
the potential of findings’ evaluation through data
synthesis. The following project elements/datasets
where synthesised through the GIS as geographical
information layers: Navigational charts, aerial orthophotos, coastline boundary (sourced from the
Hellenic Navy Hydrographic Service), Google Earth
imagery, archaeological site and survey area
boundaries, survey lines, sidescan sonar mosaics,
magnetometer data, precise positioning information,
architectonic plans, position of anchored vessels
during the survey and detected sidescan sonar and
SBP features. Fig. 23 depicts the synthesis of postprocessed magnetometer data in the area ‘C’ and
positioning information of a wreck and two cannons
(derived during the precise positioning task). Fig. 24
shows the synthesis of post-processed magnetometer and sidescan sonar data in the same area. The
two cannons are visible, as well as the extent of the
wreck and the strong backscatter from the cannonballs. Fig. 25 depicts the same findings, postprocessed magnetometer data superimposed on a
marine chart basemap, a SBP survey line and the
sub-seabed profile of the wreck along the line.
Figure 23. Synthesis of post-processed magnetometer data
and positioning data of two cannons and a wreck.
Figure 25. Synthesis of precise positioning data (cannons and
wreck) in the Area ‘C’, SBP and magnetometer data (survey line
and wreck profile) superimposed on a chart.
Fig. 26 presents the synthesis of sidescan sonar
data of the ancient harbour and the submerged
breakwater, archaeological site delimitation data
(site boundaries) and coastline information. Clearly
defined are the extent of the submerged breakwater
and the shape of the harbour entrance of which
nowadays is closed. Sand depositions are visible all
over the harbour seabed. The west breakwater rocky
slope is steep and its shape seems to be well
preserved, while the east rocky slope is gentle and
its stones are showing marks of inconsistency.
Interesting geological and habitat features are
evident east of the submerged breakwater where
hard sediments and sea grass exist. Fig. 27 and 28
refer to the same area (in the vicinity of the
submerged prehistoric settlement) and highlight the
potential of data correlation through the synthesis of
data from existing architectonic plans, magnetometer
data, precise positioning data of a wooden wreck,
SBP survey lines and sidescan sonar mosaic.
Magnetic anomalies are evident over the wreck and
the settlement ruins. Clearly defined is the extent of
the north block of settlement ruins while the ruins of
the south blocks are rather spread over the area to
an extent greater than what is recorded till now. In
the sidescan mosaic, a wreck is readily apparent as
well as a number of small scale features.
Figure 24. Synthesis of post-processed magnetometer and
sidescan sonar data. The blue ellipsis includes a wreck and the
two white ones two cannons within area ‘C’. Strong backscatter
within the blue ellipsis is caused by cannonballs.
Figure 26. Synthesis of sidescan sonar data (mosaic of the
ancient harbour and the submerged breakwater), archaeological site delimitation data (the violet dashes form part of the site
boundaries) and coastline information.
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Figure 27. Synthesis of
data in the vicinity of the
settlement
ruins
from
existing architectonic plans,
magnetometer data, precise positioning data (wreck
1) and SBP survey lines.
The potential of data correlation is clear.
Figure 28. Synthesis
of data in the vicinity of
the settlement ruins
from existing architectonic plans, magnetometer data, precise
positioning data (wreck
1), SBP survey lines
and sidescan sonar
mosaic. Large scale
features are evident
(wreck 1 in the white
ellipsis and settlement
ruins in the white
circles).
DISCUSSION
The archaeological site of Methoni lies in the shallow
waters of the homonymous bay and is exposed to
heavy waves of almost all directions due to wave
diffraction. Consequently, the wave energy along the
coasts is high. The wave energy turbidity combined
with the littoral drift action causes sediment transport
and deposition towards the north-west part of the
bay, as well as erosion of the east coast and the
shallow patches of seafloor. The revelation of the
two cannons and even the stones on top of one of
them (Fig. 11) are indicative of the seabed erosion.
Indicative of the sand transport along the surf zone
and the consequent covering and uncovering of the
settlement ruins is the fact that the same blocks of
ruins, depicted at different data acquisition periods,
do not spatially match. This offset cannot be explained solely by limitations of the survey system
positional accuracy.
The positional accuracy of the integrated sidescan
sonar system is considered at a 1.5m level. Although
the daily checked decimetre accuracy of the C-Nav
DGNSS, in situ measurements (running survey lines
in opposite directions over a distinctive feature) highlighted a 1.5m horizontal accuracy.
The accuracy degradation was caused by yaw/pitch/
roll effects of the towfish not being adequately
filtered by the navigation smoothing algorithm of the
processing software together with the variation in the
apparent bearing of targets. This variation was
caused by fluctuation of water temperature due to
water column patches of inhomogeneties (sand) that
provoked fluctuation of transmitted sound amplitude
and phase (Urick, 1983). To verify the system
positional accuracy, observed positions of features
during the sidescan survey were checked against
their derived positions from precise positioning. The
horizontal accuracy close to the breakwater slope is
considered further degraded due to ranging
distortion (Russell-Cargill, 1982). The positional
accuracy of the integrated magnetometer system is
considered at a 3.5m level, estimated through in situ
measurements (running survey lines in opposite
directions over a distinctive ferrous feature). Towfish
layback issues are believed to have largely
contributed to the stated accuracy due to boat
yawing and engine shut-offs. To verify the horizontal
accuracy, observed positions of features during the
magnetometer survey were checked against the
derived positions from precise positioning.
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The horizontal accuracy of SBP integrated system
within the archaeological site is considered at a 1m
level due to roll/pitch motion of the survey boat.
During the first day of fieldwork, the shallow waters
of Methoni Bay proved to be noisier than those of
Plymouth Sound. Hence, a by-the-bow deployment
of the sidescan towfish was tested and applied.
Although this alteration decreased the sidescan
sonar susceptibility to noise, the excessive pitch
motion of the boat caused heaving effects to be
evident throughout the sidescan sonar dataset and
especially across the area ‘C’. These effects are
readily apparent especially through the raw sidescan
sonar dataset and deteriorated the depiction of small
scale features creating an apparent topography
through replication of previous and next swath lines
(Russell-Cargill, 1982). However, the main consideration during the sidescan sonar survey was acoustic interferences. These were apparent in three
forms, namely transducer channel interference (Fig.
29), where occasionally a mirror image in sidescan
sonar channels is evident, multipath reflection interference (Fig. 30), where multiple acoustic signal
reflections from the seabed and the sea surface
resulted in depiction of non-existing artefacts close
to existing ones, and finally noise. The latter is
mostly evident in the area ‘C’. Through the literature
(Blondel, 2009), noise is explained by the dense
particle suspension in the water column, air bubbles
in the surf zone, interference fringes, sea temperature inversion and speckle. Fig. 31 is an example of
problematic data due to a combination of interference effects namely multi-path reflection interference
(false targets), air bubbles in the surf zone (parasite
backscatter close to the transducer) and speckle or
temperature inversion (shoal like patches in the
data). Since part of the area ‘C’ together with all
other survey areas were surveyed the previous days
or the same day without such problems but using
lower sonar range, it is believed that reasons for
these effects were the sea conditions and the
relatively increased sonar range that was used for
achieving a good data coverage in area ‘C’. These
effects were dealt with through wide stencilling and
gain histogram manipulation / TVG equalisation
during sidescan data post-process.
Figure 30.
False sidescan sonar artefacts due to
multipath reflection effect.
Figure 31. Coda screen dump showing problematic sidescan
sonar data due to multipath reflection interference (false targets
in red circles), air bubbles in water column (parasite backscatter
close to the transducer in the green circle) and speckle or temperature inversion (shoal like patches in the data where they do
not really exist, in the yellow circles).
The magnetometer was also affected by the shallow
water environment. The seafloor contamination, the
regional influences from anchored vessels and the
movement of the sensor due to turbulence / boat
wake (Green, 2004) led to the collection of a noisy
dataset. However, after a 3-stage data post-process,
potential targets are distinctive. The GeoPulse SBP,
when operated in water depth less than 3m, definitely reached its operational limitations. The SBP
recordings were found to be readable up to a minimum water depth of 3m and the maximum seabed
penetration was about 15m depending on Power and
Recording Length settings. The seabed and subseabed investigation, on the base of the geological
background, confirms the existence of the submerged prehistoric settlement and highlights its
wider extent. The walls of the settlement as recorded
through the sidescan dataset, compared with their
depiction through the existing architectonic plans,
Figure 29. Sidescan sonar transducer channel interference
effect. A mirror image of the ancient breakwater from the seem to be widely scattered due to the wave/
longshore drift energy or human activities.
starboard to the port channel is clear (Coda screen dump).
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Greek underwater archaeological sites, setting the
basis for a holistic management of the underwater
cultural wealth. Furthermore, the suite can be mobilised onboard the survey boats so as to provide the
EUA staff, information about the spatial distribution
of underwater antiquities on the seabed, thus reducCONCLUSIONS
ing the time spent on a site underwater. Additionally,
the suite facilitates the determination of legal aspects
The Hellenic Ephorate of Underwater Antiquities during archaeological surveys providing site bound(EUA) now has a digital tool for the sustainable man- ary monitoring.
agement of the Methoni underwater archaeological
site, through the visualisation of synthesised geo- The GE.N.ESIS project, as a new start for Greek
archaeological information. Moreover, the Ephorate maritime archaeology, has the potential for further
has a full report of features of potential archaeologi- development. A thorough study and correlation of
cal interest within the site. Apart from small-scale the numerous recorded features/artefacts in the
artefacts, highlighted are the submerged breakwater Methoni Bay may provide the EUA with a priority list
of the ancient harbour and the ruins of the sub- of features to be further investigated for years to
merged prehistoric settlement of Methoni. According come. This study will have even better results if
to the project results, the settlement ruins are se- further data post-processing is conducted. For the
verely scattered due to environmental and possibly sidescan sonar dataset, further filtering, gain histoanthropogenic factors and many of the already gram equalisation, reflection removal and additional
known settlement walls are buried while new ones process applications can improve information about
are revealed due to sediment transport. The EUA a target’s 3D dimensions and its potential of being
may evaluate the project results and implement the artefacts. The theoretical investigation of recorded
proposed management suite on the Methoni under- profiles / time series of magnetic anomalies and the
water archaeological site and even on all of the removal of magnetic regional variations may improve
information about a target’s depth, size, weight and
description. A further insight to the sub-bottom
sections can provide a clearer estimation and even a
map of the settlement extent and evidence for the
geological evolution that caused the settlement
submersion. A combined study of the above
mentioned datasets will boost the archaeological
knowledge of the Methoni site.
Fig. 32 shows the scouring effects of sea current
energy around the ruins which degrade their physical
support. Fig. 33 shows not only the presence of anchored vessels inside the officially declared archaeological site but especially on top of a wooden wreck.
Figure 32. Sidescan sonar mosaic of settlement ruins showing
halos around the ruins and close to the coast.
Figure 33. SR screen capture showing the presence of
anchored vessels (red crosses) inside the officially declared
archaeological site (bounded by the coast and the violet lines) and
especially on top of a wreck (black dashed circle) during the
survey.
At a more technical level, the investigation of
optimum towfish deployment techniques according
to various dominating factors, as well as the investigation of interference factors and optimum sonar
parameterisation in the ultra-shallow water environment may provide useful results for future surveys. A
further multibeam echo-sounder and a highresolution sidescan sonar survey of the site would
provide the EUA with 3D and updated bathymetric
information as well as updated seabed imagery
which would facilitate the monitoring of natural
processes / erosion patterns. This would enhance
the estimation of the site evolution and the promotion
of an efficient site preservation management. It is
recommended that the Hellenic Ministry of Environment, Energy and Climate Change, together with the
Hellenic Navy and the EUA, implement a Delimitation Scheme for Marine Archaeological Sites for the
protection of underwater antiquities off the Greek
coasts. Information about the archaeological site
boundaries and any navigational restrictions can be
released through the nautical charts. Finally, the
EUA is recommended to publish a Governmental
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INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
Directive providing data submission guidelines for
Project Managers conducting externally commissioned projects involving GIS, so that data submitted
to the EUA can be beneficial for the evolved
GE.N.ESIS project.


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
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
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Biris, J. (2002) A road in the South. Chora–Pylos
–Methoni. Nestor’s realm and the Mothon
stone, Athens: Ultrasound.
Blondel, P. (2009) The Handbook of Sidescan
Sonar, Chichester: Praxis.
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C&C Technologies (2012) About C-Nav, viewed 1
Sep 2012, http://www.cnavgnss.com/site.php.
3H Consulting (2012) Site Recorder 4 Software,
viewed 5 Sep 2012, http://www.3hconsulting.com/
ProductsRecorderMain.html.
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Spondylis, I. (1996) ‘‘Contribution in the study of
coastal formation in relation to the location of new
archaeological sites’’, ENALIA, IV (3/4), pp.30-37.
Spondylis, I. (2000) ‘‘Messenia county – Methoni’’,
pp.1225-1226, in ARF (eds.) Archaeological Review 55/2000. Athens: ARF
Spondylis, I. (2011) ‘‘EUA archive’’, personal communication (discussion), Dec. 2011.
University of Athens (2012) Homer’s Ilias, viewed
4 Sep 2012, http://users.uoa.gr/~nektar/arts /
tributes/omhros/il.htm
Urick (1983) Principles of Underwater Sound, 3rd
ed., California: Peninsula Publishing.
BIOGRAPHY
European Satellite Services Provider (2012a)
‘‘EGNOS Helpdesk - EGNOS Open Service Avail- Panagiotis Gkionis has been working for the
ability and Accuracy’’, personal communication Hellenic Navy for 18 years. Following training at the
(email), 29 June 2012
Hellenic Naval Academy, he embarked on his
European Satellite Services Provider (2012b) His- seagoing career as a Deputy Navigating Officer in
torical of Signal in Space Outages, viewed 25 1998. For the next 14 years he found himself within
June 2012, http://egnos-user-support.essp-sas.eu/ a wide range of warfare appointments onboard
Hellenic frigates and gunboats, qualifying as a Naviegnos_ops/data_gaps
gating Officer and Operational Training Officer. He
ESRI (2012) World Imagery, viewed 4 Sep 2012, took up his current appointment as an Assistant
http://services.arcgisonline.com/ArcGIS/rest/ Head of the Research and Planning Department
services/World_Imagery/MapServer
onboard the Hellenic Navy Hydrographic Service,
Geometrics (2012) G-882 Marine Magnetometer, following the completion of an ‘MSc Hydrography’
viewed 1 Sep 2012, http://www.geometrics.com/ programme in 2012. ([email protected])
geometrics-products/geometrics-magnetometers/g
-882-marine-magnetometer/
Green, J. (2004) Maritime Archaeology. A technical Handbook, 2nd ed., California: Elsevier Inc.
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Russell-Cargill, W. (1982) Recent Developments
in Side Scan Sonar Techniques. Cape Town:
University of Cape Town.
HNHS (1991) Tidal Information for Hellenic Harbours, Athens: HNHS.
International Oceanographic Commission (2012)
Sea Level Station Monitoring Facility, viewed 1
Sep 2012, http://www.ioc-sealevelmonitoring.org/
station.php?code=kala.
ITRF (2012) ITRS and WGS84, viewed 5 Sep
2012, ftp://itrf.ensg.ign.fr/pub/itrf/WGS84.TXT.
Lianos, N. (1987) ‘’A study of the ancient harbour
works of Methoni’’, pp.129-135, in ARF (eds.) Reconstruction-Conservation-Preservation of Monuments, Athens: ARF.
Nautical Archaeology Society (2009) Underwater
Archaeology. The NAS guide to principles and
practice, 2nd ed., Chichester: Blackwell Publishing.
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RESULTS OF OPERATIONAL SEA-WAVE MONITORING
WITH RADAR GAUGES
By Sebastian RÜTTEN, Stephan MAI, Jens WILHELMI, Theodor ZENZ,
Hartmut HEIN and Ulrich BARJENBRUCH
(German Federal Institute of Hydrology (BfG))
Abstract
The German Federal Institute of Hydrology (BfG) developed a low-cost, non-contact
sea-wave monitoring system based on a single radar sensor. A short description of the
measuring system and the analysis of wave parameters is given. Furthermore, long-term
wave measurements with this system, in combination with wind-measurements and
statistics, are used to analyse possible future changes in wave heights. The results are in
good agreement with those of other methods. Due to the good results achieved with the
single radar sensor, an extension of the system which will be capable of recording
directional information, is now under development. First results are presented in this study.
Résumé
L’Institut fédéral allemand d’hydrologie (BfG) a élaboré un système peu onéreux de
surveillance à distance des vagues à partir d’un unique sondeur radar. Une brève
description du système de mesure ainsi que l’analyse des paramètres des vagues est
donnée. De plus, les mesures à long-terme des vagues avec ce système, combinées avec
les mesures du vent et les statistiques sont utilisées pour analyser les changements futurs
possibles des hauteurs de vagues. Les résultats concordent avec ceux établis au moyen
d’autres méthodes. Du fait des bons résultats de l’unique sondeur radar, une extension du
système qui pourrait enregistrer des informations relatives à la direction, est actuellement
en cours de développement. Les premiers résultats sont présentés dans cette étude
Resumen
El Instituto Federal Alemán de Hidrología (BfG) ha desarrollado un sistema de seguimiento
de bajo coste, que no tiene contacto con la ola, basado en un sensor con un único radar.
Se proporciona en el presente artículo una breve descripción del sistema de medición y del
análisis de los parámetros de las olas. Además, las mediciones de olas por periodos largos
efectuadas con este sistema, en combinación con las medidas del viento y las estadísticas, se utilizan para analizar los posibles cambios futuros en las alturas de las olas. Los
resultados concuerdan con aquellos obtenidos mediante otros métodos. Debido a los
buenos resultados obtenidos con el sensor de radar único, una extensión del sistema, que
está ahora en fase de desarrollo, podrá registrar la información direccional. En este estudio
se presentan los primeros resultados.
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1. Introduction
Measurements of the radar monitoring system at the
“Lighthouse Alte Weser” are considered within this
New construction projects off the German coasts study to analyse possible future changes in wave
such as offshore wind farms, require the operational heights. The estimation of future changes includes
monitoring of waves nearby such offshore structures. the following steps:
While much research on the consequences of climate change has been carried out with respect to a) Analysis of current and future wind statistics from
the change of the sea level, only a few studies ana- results of a global climate model (see Section 3)
lyse its impact on waves. This may relate to the fact
b) Derivation of a transfer function of wind speed to
that no long-term records of wave parameters are
wave height (see Section 4)
available. Accordingly, several authors (Mai, 2008),
emphasized the need for reliable, continuous wave c) Applying the transfer function to map the changes
measurements. Therefore, the German Federal Insti- of the wind statistics to the changes in wave heights
tute of Hydrology (BfG) (in cooperation with the Ger- (see Section 5)
man Federal Waterways and Shipping Administration (WSV) developed a monitoring system based A description of the monitoring system at the
on a radar liquid-level sensor.
“Lighthouse Alte Weser”, data acquisition and processing is discussed in the next Section, while the
To date, four systems have proven their functionality extension towards an array of four radar sensors is
and robustness at different locations, covering a described in Section 6.
wide range of sea-state conditions. The first test assembly has been in operation at the gauge “Borkum
Südstrand” close to the North-Sea island of Borkum 2. Data and Methods
since 2002. In 2006 an additional monitoring system
was mounted at the gauge “Lighthouse Alte Weser” The data used as a basis for this study consists of
in the estuary of the rivers Jade and Weser (see Fig- wave and wind measurements recorded in the
ure 1). To further analyse the functionality under off- period from May 2006 until August 2011. Furthershore wave conditions, another system was installed more, wind data that were generated by the climate
in 2008 at the research platform “FINO 1” (http:// model” ECHAM5” were assessed for the years 1970www.fino1.de), which is approx. 45 km off the island 2090.
of Borkum. In an international context, it is used in
conjunction with the flood-defence project “Mose” in 2.1 Wave measurements
the lagoon of Venice, Italy (Wilhelmi and Barjenbruch, 2008).
Many of the sensors that are commonly used to
monitor the water-surface elevations (e.g. wave-rider
buoys or pressure gauges) have to be installed
directly in the water. This requires much maintenance as those systems are permanently exposed to
harsh environmental sea conditions such as wave
attack and corrosion. For long-term measuring
campaigns, sensors that are not directly in contact
with the water are much more easily operated and
maintained. The described monitoring system,
developed by the German Federal Institute of
Hydrology (BfG) in cooperation with the Federal
Waterways and Shipping Administration (WSV) and
the German Federal Maritime and Hydrographic
Agency (BSH) meets this criterion.
Figure 1: The operational sea-wave monitoring system at
the gauge “Lighthouse Alte Weser”.
The measuring setup consists of a commercial radar
liquid-level sensor, which is fixed to the end of a joist
that is attached to a coastal or offshore structure (as
illustrated with the “Lighthouse Alte Weser” in Figure
1). The radar sensor emits electromagnetic pulses at
a frequency of 26 GHz twice a second and, in turn,
detects these pulses when they are backscattered at
the water surface. The water surface elevation can
be easily calculated since the distance between the
radar and the water surface is proportional to the
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travelling time of each pulse. This allows the measure of water-level oscillation and, in turn, to derive
wave parameters such as the significant wave
height. For further information see Mai, S. and
Zimmermann, C. (2000).
In order to optimise the results, a very important first
step is to detect outliers and replace them by
interpolated values. This is particularly important
because the commercial radar sensors were
originally designed for level measuring in processing
industries. The outliers are located by using physical
criteria, by evaluating the possible maxima of
velocity and acceleration of the water surface, as
well as a statistical outlier test procedure. The
removed data points are then replaced by applying a
hermite polynomial which does not add artificial
extremes (Wilhelmi and Barjenbruch, 2008). The sea
-state parameters can then be calculated adopting
the Wave Analysis for Fatigue and Oceanography
(WAFO) Matlab toolbox for the analysis of random
waves and loads, developed by the University Lund/
Sweden (WAFO, 2005). One example of long-term
recordings of the significant wave height is illustrated
in Figure 2 (c).
Barjenbruch, 2008). The results of the wave-flume
experiments reveal an accuracy of less than 0.5 cm
for 95% (σ = 0.017 cm) of the recorded significant
wave heights. Other field tests were also run on the
offshore platform “FINO 1” in the North Sea. There,
the radar gauge is mounted close to the pillars of the
platform. For reference, a wave-rider buoy is
anchored at a distance of 100 meters. The comparison of the calculated significant wave heights shows
only slight deviations without a significant trend.
Thus, interactions of the sea with the structure that
might affect the wave-height measurements seem
unlikely.
2.2 Wind measurements
The monitoring programme at the “Lighthouse Alte
Weser” also includes wind parameters. A meteorological station of the Deutscher Wetter Dienst (DWD
– German national meteorological service) records
wind speed (Figure 2 b) and direction (Figure 2 a)
every minute at a height of 30m above the mean sea
level. For pre-processing, the data are converted to
local Cartesian coordinates (U=zonal wind component, V=meridional wind component) with respect to
The precision of this system was tested under labo- a reference level of 10m above the mean sea level,
ratory conditions as well as in the field (Wilhelmi and following Kleemann und Meliss (1993).
Figure 2: Illustration of the mean (bin size 1 week) wind direction (a), wind speed (b), and significant wave height (c) during
the considered period. The shaded patches indicate the standard deviation.
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2.3 Climate data
To predict future changes in significant wave
heights, additional wind-data of the Global Climate
Model “Echam5” are used. This comprehensive
general circulation model of the atmosphere was
developed by the Max Planck Institute for Meteorology (Roekner et al., 2003). The data are given on a
rotated pole grid with hourly resolution. As the
“Lighthouse Alte Weser” is not located directly on a
grid point of the model, the data needed to be interpolated linearly to the exact position. Analyses of the
interpolation methods indicate only slight differences
(average deviation of 0.1 m/s for U and V) when
choosing the nearest-neighbour method instead of
linear interpolation. The average variation of the
wind speed is calculated with regard to its directionality to include directional changes. This is of particular importance, as the wave height at the
“Lighthouse Alte Weser” strongly depends on the
wind direction.
expected scatter, there are only few wider deviations. A comparison of the times series (Figure 2 c)
shows an overall good agreement as well. For a
wind speed of 16 m/s at 240°, a significant wave
height of Hsig =2.06m is estimated by the transfer
function (1). This is in good agreement with the
results given by Mai (2008), who derived a significant wave height between 1.80m and 2.20m by
adopting the phase-averaged wave model SWAN.
Assuming that the transfer function will continue to
hold under the possible future climate as projected
by the model, the variability of the exceedance probability of the significant wave height and the wind
speed can be predicted.
3. Transfer function
Besides wind speed and direction (or more precisely:
wind stress and fetch), various additional factors influence the wave generation at the “Lighthouse Alte
Weser”. Amongst them, wind duration and water
depth are commonly assumed to be the dominant
parameters. However, at this particular observation
site, some additional aspects may also play an
important role. As the structure is located within the
estuary of the River Weser, wind-current interactions
could be relevant. Moreover, the water depth at the
site (about 11m) is strongly tide-dependent. Due to
the complexity of the processes involved, a deterministic calculation of the significant wave heights is
almost impossible.
Assuming that all time-dependent differences will
average out due to the long time period of the
recorded parameters, this study presents a simple
transfer function for the location at “Lighthouse Alte
Weser”, which depends only on the zonal (U in m/s)
and meridional (V in m/s) wind components:
(1)
One possible interpretation of this function is that the
wind stress, which is proportional to the square of
the wind speed, is the fundamental impulse,
whereas the linear correction terms include
directional dependencies. The constant offset is
partly caused by a lower measuring threshold of the
radar gauge. A comparison of the calculated and
measured significant wave heights is shown in
Figure 3, resulting in a correlation coefficient c=0.84
with an R2 goodness of fit of 0.71. Besides the
Figure 3: Scatter plot of the comparison of significant wave
heights.
4. Prediction of wave-height changes
As a first step, a quantile-mapping-based bias correction for the considered location was made for the
wind statistics of the global climate model. Thereupon, exceedance probabilities of wind speed and,
by applying the transfer function, wave heights were
calculated.
A general increase of the wind speed along with an
increase of the significant wave height within the
next coming years is suggested by the model (see
Figure 4). For the period from 2006 to 2045, an average increase of the 99% quantile of the significant
wave height by 0.33 cm/year is indicated. In the subsequent 30 years, the model predicts an average
increase that is slightly lower (0.17 cm/year). On the
average of the period from 2006 to 2075, the derived
change of the significant wave height at the
”Lighthouse Alte Weser” suggests an increase of the
99% quantile by 0.26 cm/year.
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Figure 4: Exceedance probabilities of wind speed and significant wave heights at the “Lighthouse Alte Weser” within
three time periods.
The uncertainty of the predicted wind speed distribution can lead to wide discrepancies in the results.
Mai and Zimmermann (2004) examined a climate
scenario for the year 2050 near Solthörn, which is
approximately 50 km east of the observation site.
They determined an increase of the 99% quantile of
the significant wave height by 0.4cm/year, which is
close to the results estimated in this study. The slight
difference may be attributed to the fact that the water
depth near Solthörn is less than at the ”Lighthouse
Alte Weser”. Therefore, climate-change related rise
of water level causes an increased change in wave
height. In contrast to the aforementioned good
agreement, Weisse et al. (2003) proposed a trend of
1.2cm/year increase for the years 1958-2001 as determined by wind wave hind casts. This spread in the
estimates of changes in significant wave height emphasizes the need for more continuous monitoring of
sea-state parameters, including not only significant
wave height and wave period but also wave direction.
which monitor water surface elevation at one point
and thus, sea state parameters, as wave heights and
wave periods, is enlarged towards monitoring wave
direction. This development of the German Federal
Institute of Hydrology (BfG) makes use of an array of
commercial radar sensors. The technique is based
on simultaneous recordings of wave profiles at
several fixed positions. Basically, the crosscovariance spectral densities between these records
are used to estimate the directional spectrum.
Further information is given in the literature, e.g.
Benoit et al. (1997).
While designing such an array, the following relevant
guidelines should be taken into account (Goda,
1985) - to fully exploit the information of all sensor
locations, the duplication of vector distances should
be avoided. Furthermore, the array size is limited, on
the one hand, by the smallest wavelength for which
the directional analysis is to be made, because the
minimum separation distance between a pair of
wave gauges has to be less than one half of this
5. Extension of the existing monitoring system wavelength. On the other hand, the directional
by measurements of directional information
resolution of the array increases as the maximum
distance between the wave gauges increases.
Precise recordings of wave direction would improve,
on the one hand, numerical modelling of sea states However, the maximum size of the array is often
(Haver and Nyhus, 1986) and, on the other hand, the limited by the construction of the offshore or coastal
design of coastal and offshore structures. Bowers et structure to which it is attached. For an operational
al. (2000) underline that the maximum hawser ten- use of radar arrays, the number of sensors should
sion at some structures may occur when wind and be limited to three or four in order to keep it as simwaves are at 60-90°. They point out that the simple ple and cost-effective as possible.
assumption of an aligned wind and wave direction is
often invalid. They monitored a difference up to 60° 5.1 Laboratory tests and PC based simulations
before the storm is fully developed. Even at the peak
of a storm, differences of 10-30° are common.
The applicability of an array of three commercial
radar liquid-level sensors to measure the directional
Therefore the radar based wave-gauging stations, wave spectrum under the constraints mentioned
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(3)
above was tested by numerical simulations and
laboratory experiments. Since the cross-covariance
method (Goda, 1985) presumes simultaneous
records of the water-surface elevation at all sensor
locations, the impact of the uncertainty in the
simultaneity of measurements within the used
array-dimension was analysed under laboratory With each parameter setting, 100 simulation runs
conditions.
( N ) were performed. Figure 5 illustrates the resolution of a delta array, consisting of three sensors at
The laboratory experiment is set up in such a way the apexes of an equilateral triangle, as proposed by
that all commercial radar sensors record a distance Goda (1985), for different edge lengths. On the
to a reflector, moving along a known track. There- x-coordinate, the standard deviation  of an asfore, the difference in the measured distance can be sumed Gaussian-distributed uncertainty in time is
assigned to a time lag. The resulting uncertainty of shown.
the measuring time of all sensors was found to be
Gaussian-distributed with a standard deviation of
 =0.05s. In addition to the uncertainty in
measuring time, a standard deviation of the distance
measured by the radar sensors of 0.5 cm (see
Section 3.1) was considered. With these uncertainties in measuring time and distance, the optimal
design of the radar gauge array was derived using
the following numerical methodology:
The starting point was a measured time series of
water-level elevations ( 1 (t ) ) at the location of one
radar sensor within the array. This time series was
then assigned to the other sensor locations within
the array prescribing wave velocity ( v ) and the
vectorial distance of each sensor location to the location of the first sensor ( n i ) using:
(2)
Figure 5: Resolving power of the radar gauge array,
determined by adopting simulated computer data. The mean
absolute deviation of the estimated direction is shown for
Gaussian-distributed time lags with standard deviations up to
0.6 s. Additionally, the dependence on the edge length can be
examined.
Afterwards, the time series of these simulated
surface elevations of all sensor positions were
digitized with a frequency of 2 Hz, including possible
uncertainties in time and distance of the measurement. The resulting dataset was used to calculate
the directional spectral density, adopting the
DIWASP Matlab toolbox, developed at the Coastal
Oceanography Group, Centre for Water Research,
at
the
University
of
Western
Australia,
Perth (Johnson, 2002). Within this toolbox, the
extended maximum entropy method (Hashimoto et
al., 1993) was selected for data analysis. As the
simulated wave field is unidirectional, only the
dominant wave direction is evaluated for accuracy
examination. For the analysis of directional resolution, the mean absolute deviation ( e ) of the
estimated direction  out from the prescribed direction
 in is regarded:
The directional resolution of the simulated radar
gauge array increases as the distance between the
sensor locations increases or the time lag between
all measuring devices becomes smaller. For a
standard deviation of 0.05s a mean absolute
deviation of e=5.2° was found for the smallest
considered edge length of 2m. The resolution further
improved to e=3.2° for a length of 3m and e=2.8° for
an edge length of 4m. An expansion of the array size
to 5m or 7m leads to a mean absolute deviation of
e=2.0°. Despite the measuring time delay of the
chosen radar liquid-level sensors, sufficiently
accurate results will probably be achieved for edge
lengths larger than 3m. On this basis, a triangular
array design with edge lengths larger than 3m is
recommended.
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5.2 Onsite implementation of the radar array is sufficient to yield a good estimate of the two
system
dimensional spectrum, provided the spacings
between the probes were chosen carefully. In
For a first field test of the radar array, an edge length addition, a fourth sensor can be particularly advantaof 3.5m was chosen. The prototype system was geous in situations in which one sensor records
mounted at the gauge “Borkum Südstrand” in July, erroneous data or even stops working.
2012. This location is particularly suitable as it is
close to a revetment. Since information about direc- 5.3 First results of the extended monitoring
tionality is necessary for revetment design, it is a system
potential operational site. Here, the wind blows
predominantly from North-west. From this direction, First measurements of the extended monitoring
the sea state is not influenced by obstacles like system were analyzed for a time period of 30
islands or shoals, while passing ships may generate minutes starting on 03.11.2012 at 11 pm. The
waves there (Wilhelmi and Barjenbruch, 2008). The recorded significant wave height is H-sig =0.76m with
water depth at this site is approximately 8m (Mai et a mean wave period of T m=3.57s. Figure 7 presents
al., 2010).
both the normalized spectral density, on the one
hand, and, on the other hand, the direction as a
The arrangement of the radar gauge array is illus- function of frequency.
trated in Figure 6. A star array (an extension of the
delta shaped array with an additional sensor in the
centre) was preferred for the first test assembly to
further improve the directional resolution, since
numerical results revealed that the error in wave
direction, described in this study by the mean
absolute deviation ( e ), further decreases by 59%.
Figure 7: First results from the radar gauge array. The
normalized spectral density (blue) and the direction of the
waves (red) are illustrated as functions of frequency. The black
dotted line denotes the mean wind direction.
The dominant energy input is induced by windgenerated waves. The peak frequency is approx.
0.19Hz. Swell contributes only a small amount of
energy to this sea state (small peak at approx.
0.07Hz). The directional information is estimated by
applying the direct Fourier transformation method.
For comparison, the mean wind direction  ind=250°
at a mean wind speed of 12m/s is delineated in
black. In the presented case, the wave direction
coincides with the wind direction in the range of their
Figure 6: First test assembly at the gauge "Borkum
mean intensities, since the wave approach is almost
Südstrand". The specially developed triangular extension
perpendicular to the beach and this is also the
of the gauge is equipped with four radar liquid-level
predominant wind direction at this particular site.
sensors.
Wider differences were found only in those
frequency components of the wave spectrum that
This choice is also supported by Mobarek (1965), contain very little energy.
who states that a four-detector array of wave gauges
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INTERNATIONAL HYDROGRAPHIC REVIEW
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6. Conclusion
As demonstrated in this study, the monitoring system
based on a radar liquid-level sensor, developed by
the German Federal Institute of Hydrology (BfG) has
proven its suitability for long-term measurements. In
combination with wind statistics from a global climate
model, this data was successfully used to examine
possible future changes in sea-wave heights. Despite the simplicity of the presented transfer function
from wind speed to wave heights, the results are in
good agreement with that of other methods. The derived change in the significant wave height at the
“Lighthouse Alte Weser” suggests an average increase of the 99% quantile by 0.26 cm/year until the
year 2075. To detect long-term trends more accurately, continuous monitoring of sea-state parameters is indispensable.
Special emphasis shall be given to the fact that the
system can be extended towards gathering directional information of the sea state, while the advantages (e.g. low costs and maintenance and high reliability) are retained. The first test assembly consisting of a star-shaped array of four radar sensors produced encouraging results.
REFERENCES
Benoit, M., Frigaard, P. and H. A. Schaffer, (1997).
“Analyzing multidirectional wave spectra: A tentative
classification of available methods”. Proc. Seminar
on Multidirectional Waves and their Interaction with
Structures, San Francisco, CA, International
Assembly of Hydraulic Research, 131–158.
Bowers, J.A., Morton, I.D. and Mould, G.I. (2000).
“Directional statistics of the wind and waves”. Applied Ocean Research 22. 13-22.
Haver,S. and Nyhus, K.A. (1986). “A wave climate
description for long term response calculations”. Proceedings of the fifth international offshore mechanics
and Arctic engeneering symposium, Vol 4, 27-34.
Goda, Y. (1985). “Random seas and design of
maritime structures”. Univ. Tokyo Press.
Hashimoto, N., Nagai, T., Asai, T., Sugahara, K.,
(1993). “Extension of the maximum entropy principle
method for estimating directional ocean wave
spectrum”. Report of the Port and Harbour Research
Institute 32 (1), 3 –25.
7. Outlook
Johnson, D. (2002). “DIWASP, a directional wave
spectra toolbox for MATLAB®: User Manual”. ReThe comparison of the directions of the waves to that search Report WP-1601-DJ, Centre for Water Reof the wind can only be considered as a first indica- search, University of Western Australia.
tion for the efficiency of the new developed directional measurement system, as significant deviations Kleemann, M. and Meliss, M. (1993). Regenerative
are often noted in the literature. To evaluate its accu- Energiequellen. Springer Verlag.
racy more precisely, a Datawell Directional Waverider buoy MKIII will be deployed near to the Mai, S. and Zimmermann, C. (2000). “Applicability of
gauge “Borkum Südstrand”. In addition, a second Radar Level Gauges in Wave Monitoring”. Proc. of
test assembly is planned to be installed at the re- the 2nd Int. Conf. Port Development & Coastal Envisearch platform “FINO 1”. This observation site is ronment. Varna, Bulgaria.
located close to the German offshore wind farm
“Alpha Ventus”, approximately 45 km offshore, Mai, S. and Zimmermann, C. (2004). “Veränderung
where sea states conditions differ considerably from der Seegangsbedingungen an den Küsten von Jade
those at the gauge “Borkum Südstrand”. Moreover, und Weser als Folge der Klimaänderung”. Coastline
there are hardly any obstacles such as islands in the Reports 1. 93 – 100.
vicinity of this site that might influence the sea state
Mai, S. (2008). “Statistics of Waves in the Estuaries
in any direction. Furthermore, larger waves and
of the Rivers Ems and Weser-Measurement vs. Nucrossing seas are likely to occur at “FINO 1”.
merical Wave Model”. COPEDEC VII, Dubai.
Acknowledgement
Mai, S., Wilhelmi, J., Barjenbruch, U. (2010). “Wave
height distributions in shallow waters”. Proceedings
The results of this study are partly taken from the of 32nd International Conference on Coastal Engi“KLIWAS” research programme and from the BfG neering, Shanghai, China.
project “RiseARaF”, both funded by the Federal
Ministry of Transport, Building and Urban Develop- Mobarek, I.E.S., (1965), Directional wave spectra of
ment (BMVBS). The authors thank Anette Ganske laboratory wind waves. Proceedings A.S.C.E., WW
(Deutscher Wetterdienst, Hamburg) for support. The 3, 91-116.
authors would also like to thank the Water and Shipping offices (WSA) Bremerhaven and Emden for the Roeckner, E., Bäuml, G., Bonaventura, L., Brokopf,
installation and maintenance of the radar gauges.
44
INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
R., Esch, M., Giorgetta, M., Hagemann, S.,Kirchner,
I., Kornblueh, L., Manzini, E., Rhodin, A., Schlese,
U., Schulzweida, U., and Tompkins,A. (2003). “The
atmospheric general circulation model ECHAM5.
PART I: Model description”,Tech. rep., Max Planck
Institute for Meteorology, MPI-Report 349.
Germany. His Ph.D. thesis was in the field of coastal
engineering. From 1989 to 1995, he was a student
research assistant at the Alfred-Wegener Institute for
Maritime and Polar Research. From 1990 to 1994 he
was a student research assistant at the University of
Bremen and between 1995 and 2004, Stephan was
a research assistant at the Franzius-Institute for WaWAFO. (2005). “A Matlab toolbox for analysis of terways and Coastal Engineering.
random waves and loads" Version 2.1.1, The WAFO (Email: [email protected])
Group, Lund Institute of Technology, Lund
University, 2005.
Jens Wilhelmi is a Physics engineer and since
2000, has been employed at the German Federal
Wang, X. L., Zwiers, F. W. and Swail, V. R. (2003). Institute of Hydrology evaluating new measurement
“North Atlantic Ocean Wave Climate Change techniques and data transmission.
Scenarios for the Twenty-First Century”. J. climate, (Email: [email protected])
Vol. 17.
Ted Zenz is a Civil Engineer and electronic techniWeisse, R., Feser, F. and Günther, H. (2003), “Wind- cian with studies in electronics and Civil Engineering
und Seegangsklimatologie 1958-2001 für die at the University of Applied Science in Koblenz. He
südliche Nordsee basierend auf Modellrechnungen”, has been with the Federal Institute of Hydrology in
GKSS Report.
Koblenz, Germany since 1989.
Wilhelmi, J. and U. Barjenbruch. (2008). “Application (Email: [email protected])
of Radar gauges to measure the water level and the
state of the sea”. Proceedings of 31st International Dr. Hartmut Hein is a Hydrographic Surveyor with
Conference on Coastal Engineering, Hamburg, studies in surveying at the University of Applied
Science Hamburg. He has a Ph.D. with his thesis in
Germany.
the field of oceanography. In the period 2003 to
2009, he was a research assistant at the University
CONTACT DETAILS
of Hamburg. Since 2009, Hartmut has been at the
Federal Institute of Hydrology in Koblenz, Germany.
Sebastian Rütten
(Email: [email protected])
Federal Institute of Hydrology (BfG)
Department of Hydrometry and Hydrological Survey
Am Mainzer Tor 1
Dr. Ulrich Barjenbruch is a Physicist with studies in
56068 Koblenz
Electrical Engineering and Physics at the University
Germany
of Hannover. His Ph.D. thesis was in the field of solid
Tel.: +49 261 1306 5336
state Physics. Ulrich has been the Chief of
Email: [email protected]
Department: Hydrometry and Hydrological Survey at
the German Federal Institute of Hydrology since
BIOGRAPHIES
2006.
Sebastian Rütten is a Physicist and since 2012 has
been at the Federal Institute of Hydrology in
Koblenz, Germany. He studied Physics at the
University of Cologne, a Diploma thesis in Oceanography at the University of Bremen and during 2007 to
2009, was a student research assistant at the
University of Cologne. From 2009 to 2011,
Sebastian was engaged as a student research assistant at the University of Bremen and participated in
two North Atlantic expeditions on the research vessel Meteor.
(Email: [email protected])
His previous experience follows:
- 1984 to 1988: research associate at the Institute
of solid-state physics, Technical University of
Hannover
- 1989: research associate at the institute of
physical and theoretical chemistry, University of
Tübingen
- 1989 to 1995: research associate at the section of
measurement
Kassel
and
technology,
University
of
- 1995: state doctorate in “Electrical measurement
technology”, theme: “Highly sensitive measureDr.-Ing. Stephan Mai is a Physicist and Civil
ment of magnetic fields”
Engineer and since 2005 has been at the Federal
Institute of Hydrology in Koblenz, Germany. He - 1995: self-employed (engineering office), construction and application of highly sensitive magnetic
studied Physics at the University of Bremen and Civil
field sensors
Engineering at the University of Hannover in
45
INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
- 1995 to 1997: assistant professor at the University
of Kassel
technology)
(section
of
measurement
and
- 1997 to 2006: Chief of Department Physics,
Instruments and Measurements at the German
Federal Institute of Hydrology.
(Email: [email protected])
46
INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
ANOMALOUS ECDIS OPERATIONS
By Dr. Mohamed I. MOHASSEB
(Navigation Division in the Egyptian Naval Hydrographic Office &
Arab Academy for Science and Technology and Maritime Transport - Alexandria, Egypt)
Abstract
The Electronic Chart Display and Information System (ECDIS), in conjunction with other
recent technologies such as Radar and Automatic Information System (AIS) has practical
benefits to facilitate safe navigation and bridge watchkeeping. The ECDIS capability
however is suffering from ongoing issues including Electronic Navigation Chart (ENC) data
encoding inconsistencies, differences between the content shown on paper charts and the
corresponding ENC, overlapping and conflicting ENC coverage and the interpretation and
application of the IHO’s S-52 Presentation Library to display ENC symbols. This paper
addresses the International Hydrographic Organization’s (IHO) effort to collect, analyze
and resolve these problems so that they can be addressed by the appropriate agencies
and organizations in order to maintain safety of navigation.
Résumé
Le système de visualisation des cartes électroniques et d’information (ECDIS),
conjointement avec d’autres technologies récentes, telles que le radar et les AIS,
présente des avantages pratiques qui favorisent la sécurité de la navigation et les
pratiques de veille sur la passerelle. La capacité de l’ECDIS souffre toutefois de
problèmes récurrents y compris des incohérences dans le codage des données des
cartes électroniques de navigation (ENC), des différences entre le contenu qui apparaît
sur les cartes papier et les ENC correspondantes, ou de l’existence de chevauchements
et de couverture ENC contradictoires et de l’interprétation et de l’application de la
Bibliothèque de présentation de la S-52 de l’OHI pour présenter les symboles des ENC.
Cet article aborde les efforts de l’Organisation hydrographique internationale pour
rassembler, analyser et résoudre ces problèmes afin qu’ils puissent être résolus par les
agences et organes appropriés dans le but de maintenir la sécurité de la navigation.
Resumen
El Sistema de Información y de Visualización de la Carta Electrónica (ECDIS), junto con
otras tecnologías recientes como el radar y el Sistema de Identificación Automática (AIS),
tiene beneficios prácticos para facilitar una navegación segura y para las tareas de
guardia en el puente. Sin embargo la capacidad del ECDIS se ve afectada por temas en
desarolloque incluyen: incoherencias en la codificación de datos de la Carta Electrónica
de Navegación (ENC), diferencias entre el contenido mostrado en las cartas de papel y la
ENC correspondiente, el solapamiento y una cobertura discordante de ENCs y la
interpretación y aplicación de la Publicación S-52 de la OHI – Biblioteca de Presentación,
para representar los símbolos ENC. Este artículo trata sobre el esfuerzo de la Organización Hidrográfica Internacional para reunir, analizar y resolver estos problemas, de modo
que puedan ser tratados por las agencias y organizaciones adecuadas para mantener la
seguridad de la navegación.
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INTERNATIONAL HYDROGRAPHIC REVIEW
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Importance of ECDIS
facturers, type-approval laboratories, training
establishments, professional mariner and industry bodies, and maritime Administrations. [4]
Numerous studies have been conducted concerning
the importance of Electronic Chart Display and

The International Hydrographic Bureau (IHB)
Information System (ECDIS). Some of these studies
hosted the workshop in Monaco on 15-16
concern the physical state of the mariner whilst other
February 2011. The workshop was attended by
studies related the mental state whilst using the
37 leading representatives from stakeholder
ECDIS technology. A study conducted by the
groups including the IMO Secretariat, IHO and
Russian Federation [2], found a reduction in a user's
IMO
Member
States,
Intergovernmental
pulse rate by some 10-12% when using ECDIS
Organizations, Non-Governmental International
compared with others who were not using it. The
Organizations, data service providers, ECDIS
mariner’s ability to handle navigationally-challenging
manufacturers and type-approval authorities.
areas such as maneuvering to avoid a collision with
The Chair and Vice-Chairs of IHO HSSC and
other vessels in close proximity, is significantly
TSMAD working groups also attended the
improved when using ECDIS. Another important
workshop. [5]
benefit is the intelligent integration of the radar
image and Automatic Identification System (AIS)  UKHO has found over 900 differences between
information with the ECDIS display brings further
paper charts and their equivalent ENC product
practical benefits to facilitate safe navigation and
that have potential significant implications for
bridge watch keeping. ECDIS is also used for
navigation safety. These differences cover 400
pre-sailing activities such as voyage planning,
ENC cells from 30 different producer nations. [6]
execution and monitoring. [1]
IHO Standards for ECDIS
ECDIS Anomalies
IHO Circular Letter 46/2011 [7] identified the current
Because of the benefits that ECDIS provides, status of the IHO ECDIS related Standards and
several concerns have been raised about identified these are listed in Table 1.
ECDIS anomalies. These anomalies could be that
IHO Standard
Name
Effective date of
ECDIS equipment at sea does not perform optimally
latest edition
or as expected because of shortcomings in the
S-57 Edition 3.1
IHO Transfer StanNovember 2000
nature of the ENC data, the ECDIS software
dard for Digital
implementation, the implementation of current IHO
Hydrographic Data
ECDIS-related standards, and/or various combina- S-52 Presentation IHO Presentation
January 2008
tions of these and other factors.
Library Edition 3.4
Library for ECDIS
International Efforts
S-63 Edition 1.1
IHO Data Protection
Scheme
March 2008
Several efforts have taken place internationally to
address these ECDIS anomalies. Examples of Table 1. IHO ECDIS Standards
these efforts are listed below:
Based on the above standards, any ECDIS

At the 88th session of the International Maritime purchased before 1 January 2008 will not have been
Organization (IMO) Maritime Safety Committee built or type-tested in accordance with the latest IHO
(MSC), Japan, Norway, the United Kingdom, the chart standards. Mariners, whose ECDIS software is
International Chamber of Shipping (ICS), and the not up to date, should contact the manufacturer or
International Federation of Shipmasters’ Asso- the service agent for assistance. [7]
ciations
(IFSMA)
submitted
document
MSC88/25/6 on “Operating anomalies identified One of the main concerns is that the ECDIS software
within ECDIS”. [3]
is not conforming to the latest IHO standards. It
should be possible to interrogate the operating

UK made a presentation entitled “ECDIS Anomasoftware in any ECDIS to determine if the latest
lies and Safety Implications”. [3]
standards have been implemented by the manufac
The UKHO and the UK Maritime and Coastguard turer. However, the method for finding this
Agency co-hosted a technical workshop in information differs from system to system and is not
London attended by invited experts to review the always easy to locate. In any case, it does not neccurrent situation with reported ECDIS issues. essarily guarantee that the latest IHO standards
The participants comprised 23 leading ECDIS have been comprehensively implemented. For these
experts from IHO Member States, ECDIS manu- reasons, the IHO developed a test data set in the
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INTERNATIONAL HYDROGRAPHIC REVIEW
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form of three dummy ENCs that mariners can use to Figures 2 and 3 illustrate how the HYPACK ENC
check if the latest IHO Standards have been Editor 12.0.0.0 and CARIS Easy View 2 display the
implemented in their equipment. All together, there features.
are six different tests designed to check the status of
the ECDIS [7]. The tests require that you load the
three dummy ENC cells. The six tests involve
looking carefully at various chart objects contained in
the ENC cells.
For this paper, 5 of the 6 tests have been consolidated into 3 Checks as follows:

Check 1 – Display of navigation areas recently
recognized by the IMO.

Check 2 – Display of complex lights.

Check 3 – Display of underwater features and
isolated dangers.
Figure 1. Correct display of 4 objects based on the S-52
Presentation Library edition 3.4
A final test involving the detection of objects by route
checking in voyage planning mode was not included
in a Check as the software being tested are not
ECDIS equipment but ENC viewing software.
Check Results
Even though these tests are designed to check
ECDIS performance, they have been run on two
ENC viewers. The ENC viewers are HYPACK ENC
Editor 12.0.0.0 and CARIS Easy View 2 (freely Figure 2. HYPACK ENC Editor 12.0.0.0 depiction of the 4 objects
available from the CARIS home site). The tests were
conducted on 16th June 2012.
Check 1 – Display of navigation areas recently
recognized by the IMO
Figure 1 illustrates four symbols that should be
displayed to highlight navigation areas that were
recently adopted by the IMO and resulted in changes
to S-57. These areas include:

Archipelagic Sea Lane (ASL)

Environmentally Sensitive Sea Area (ESSA)

Particularly Sensitive Sea Area (PSSA)

Also included in this Test is an encoding of a new
IHO object called NEWOBJ which will display as
a black square and have labeled text
“Presentation Library 3.4”. This test is to display a
new chart object without any change to the IHO
Presentation Library.
Figure 3. CARIS Easy View 2 depiction of the 4 objects
As shown in Figures 2 and 3, HYPACK ENC Editor
12.0.0.0 managed to show Archipelagic Sea Lane,
Environmentally Sensitive Sea Area and Particularly
Sensitive Sea Area symbology correctly but CARIS
Easy View 2 could not. However, CARIS Easy View
2 shows the Presentation Library 3.4 symbology but
HYPACK ENC Editor 12.0.0.0 doesn't show it.
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Check 2 – Display of complex lights
As shown in Figures 5 and 6, both packages fail to
depict the correct sector light symbol meanwhile
Figure 4 shows how complex light should be shown both depict the light characteristics correctly.
along with light characteristics.
Check 3 – Display of underwater features and
isolated dangers
The display of obstructions and isolated dangers in
ECDIS is complex. Unfortunately, not all ECDIS
equipment performs as intended by the IHO
Standards. This test is intended to confirm that the
more common display issues are not present in the
ECDIS display.
Figure 4. Correct display of complex lights objects.
Figure 7. Correct display of isolated dangers in OTHER mode
with 10m safety contour/safety depth
Figure 5. HYPACK ENC Editor 12.0.0.0 depiction of the complex
light objects.
Figure 8. HYPACK ENC Editor 12.0.0.0 depiction of the isolated
dangers.
Figure 6. CARIS Easy View 2 depiction of the complex light
objects
Figure 9. . CARIS Easy View 2 depiction of the isolated dangers.
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INTERNATIONAL HYDROGRAPHIC REVIEW
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According to Figures 8 and 9, both packages depict 
the isolated dangerous symbols labeled 9 and 10
correctly.
The checks that have produced negative results
vary between manufacturers and different software versions from the same manufacturer.

No check reveals the same failure across all 15
manufacturers’ systems reported to the IHB. This
appears to confirm that certain parts of the
requirements of the ECDIS standards have been
interpreted and implemented in different ways by
different manufacturers. [9]
The results of these tests have been sent to both
software manufactures. HYPACK Company
upgraded its ENC Editor 12.0.0.0 to comply with IHO
standards and will be released in the next version.
ECDIS Validation Test Results
ECDIS Non-Conformance – recommended
The IHO’s ENC Data Presentation and Performance
actions
Check was issued in October 2011. By the end of
February 2012, 500 reports from testing parties had

If after applying the IHO test and finding that the
been received. These reports covered 15 out of
ECDIS is not complying, the mariner should
approximately 25 recognized and widely used type‐
contact the manufacturer to upgrade the ECDIS
approved ECDIS manufacturers.
software. Untill ECDIS has been upgraded it is
recommended to perform certain actions
The results were divided into three major findings;
depending on what test your ECDIS fails to
satisfy.
 One third of the systems fulfill the check and

During the test, the following areas should be
function as expected;
displayed - ASL, ESSA, PSSA, as well as the
 A further third display all significant underwater
New Object. If these areas are not displayed on
features, including underwater obstructions, but
the ECDIS screen, and the borders contain “?”
the isolated danger symbol required to be shown
marks, interrogate all “?-?-?” type borders or “?”
under certain conditions is not always used; and
symbols, using the function usually known as
Chart Query or Chart Pick. If any symbol could
 Most of the remaining third failed to display some
not be seen at all, it is essential to consult other
significant underwater features in the "Standard"
nautical publications during the route planning
display mode. All these features are however
phase including Sailing Directions and Mariners‟
displayed in the “Full display” or “All display”
Routing Guides, to identify the existence of
modes. [8]
ESSA, PSSA and ASL and then include them
manually as Mariners Objects in the ECDIS.
The analysis of results that were received by IHO
shows that:

Symbols of different sector light and light
A significant number of ships reported that they
were unable to clearly identify the recently IMOadopted ASL, PSSA or ESSA objects on the
ECDIS display;

Ships reported that lights with complex characteristics such as multiple colored sectors were
not displayed as intended by the IHO standards;
characteristics should be displayed. If they are
not shown at all or not shown correctly, notes
should be recorded.

The display of underwater features and isolated 
dangers was reported as variable across the
different manufacturers’ systems. However in
most cases the display gave a safe, if not entirely
correct, interpretation of the ENC data;

A high proportion of ships reported that navigationally significant objects, such as certain land
features, “area to be avoided” and marine aqua- 
culture installations, did not raise an appropriate
warning in the route checking mode of ECDIS;
Among the objects that should be displayed
during the test, are underwater and isolated
dangers. If any of the objects are not displayed, it
is essential to consult other sources of information such as paper charts and publications to
ensure that all underwater dangers and isolated
dangers are identified.



Few ships in the nearly 500 reports received by
the IHB, appear to have an ECDIS that successfully passed all parts of the IHO checks;
51
During the voyage planning phase, cross-check
the information about lights shown on ECDIS
with the information shown in the relevant List of
Lights.
The last check on this test is the detection of
objects by route checking in voyage planning,
mode. If hazardous objects don't raise alarms in
voyage planning, it is recommended to carry out
a visual examination so as to detect them and to
highlight them manually in ECDIS as "manual
updates".
INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
Conclusions
ECDIS is an important enabling technology to
improve navigation safety. ECDIS software, just like
any system on the ship's bridge, must be maintained
and kept up to date. The mariner’s awareness of the
need to upgrade ECDIS software should be
improved. In using ECDIS systems that fail to
adequately show underwater features, the mariner
must navigate in conjunction with the paper chart to
ensure that all wrecks and underwater obstructions
can be properly identified.
References

[1] DEVELOPMENT OF CARRIAGE
REQUIREMENTS FOR ECDIS, Proposal to
amend regulation 19 of SOLAS chapter V.

[2] DEVELOPMENT OF CARRIAGE REQUIREMENTS FOR ECDIS, IMO, NAV 54/14,
2008.

[3] International Hydrographic Organization,
Circular Letter, 83/2010, Monaco, 2010.

[4] International Hydrographic Organization,
Circular Letter, 86/2010, Monaco, 2010.

[5] International Hydrographic Organization,
Circular Letter, 19/2011, Monaco, 2011.

[6] International Hydrographic Organization,
Circular Letter, 40/2012, Monaco, 2012.

[7] International Hydrographic Organization,
Circular Letter, 46/2011, Monaco, 2011.

[8] International Hydrographic Organization,
Circular Letter, 33/2012, Monaco, 2012.

[9] International Hydrographic Organization,
Circular Letter, 18/2012, Monaco, 2012.
Biography
Dr. Mohasseb is currently the head of the Navigation Division in the Egyptian Naval Hydrographic
Office and a Hydrographic survey instructor at the
Arab Academy for Science and Technology and
Maritime Transport (AASTMT), Alexandria, Egypt.
He received his CAT B certificate from US Naval
Oceanographic Office in 1998, his Master of Science
degree from AASTMT in 2001 and a PhD degree
from AASTMT in 2006 with the award of best
dissertation. He then achieved CAT A certification
and his Master of Science with the award of
Outstanding Academic and Practical Performance
from the University of Southern Mississippi in 2009.
e-mail : [email protected]
cell phone: (+201001448673)
52
Note from IHB :
At the time of publication, IHB can report
significant progress has been made by ECDIS
manufacturers and software producers to
address the anomalies identified. As a result of
discussions between IHO, IMO and various key
stakeholders, considerable efforts have been
made by manufacturers to contact system users
to provide up-grades which meet the IHO
Standards. Performance monitoring remains an
ongoing task. For further information see the
IHO website: ENC & ECDIS.
INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
A TECHNICAL METHOD ON CALCULATING THE LENGTH OF COASTLINE
FOR COMPARISON PURPOSES
Laurent LOUVART
(Eng. Corps & Hydrograph., SHOM - FRANCE)
on behalf of the IHO Correspondence Group
Abstract
A quick web search illustrates the wide variation in the quoted lengths of the coastline of a
unique State, with ratios from 1 to 100 and in some examples, even more. This illustrates the
need for a common measuring method. The length of a coastline, for the purpose of comparison between States, can be calculated according to the guidance and specifications
described in this paper.
This specification describes a harmonized approach to determining the length of a coastline.
It may only be relevant for comparison purposes and should not to be regarded as definitive
nor suitable for all purposes. Based on official ENC datasets, the advantage of this method is
that it gives comparable results that can be easily verified.
Background
Following a request from the European Commission, the 20th IHO CHRIS Meeting
(November 2008) encouraged the creation of a Correspondence Group (CG) aimed at
harmonizing the way Member States define and measure the length of their national
coastlines.
France volunteered to coordinate such a CG to study the feasibility of such standardization
and members were invited to join the group. The HSSC-2 meeting in October 2010 invited
the CG on the Definition and Length of Coastline to complete its work by HSSC-3.
The CG met on 30-31 March 2011 in Brest, France, with participation from Germany, Finland,
Spain, Cyprus, USA, Slovenia and France. A first draft method was proposed to HSSC-3 in
2011. This last version clarified the aspects related to determinations between S-57 Usage
Band ENC’s.
Users’ need and purposes for length of coastline
The CG found that there are no clear legal, or other obligations to define how the length of
coastline is determined. It is possible to define the length for various different purposes such
as, administrative and comparison purposes (allocating fishing quotas, referencing aquaculture production statistics, coastal zone management, defining “hydrographic interest”, etc.),
environmental protection (for example, evaluating response capacity requirements) and
scientific purposes.
It was found that there are often several lengths available for the calculated or estimated
length of coastlines, but only few metadata is associated with these values. There are many
worldwide digital source data sets available. There also exist several GIS software tools
available to make the calculations.
The CG recognized that the coastline is by nature a fractal object, so it is not possible to
provide an unambiguous length. The length may be calculated in as much detail as is desired
and the length may therefore grow to infinity. There is never one simple solution (see
Appendix 1).
However, the CG noted that there are often requirements to be able to compare the length of
coastlines between States for certain administrative purposes. Thus a standardised method
for calculating these lengths is required.
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General requirements
The CG noted that in order to develop a harmonised approach, there are many issues that must be clarified
before the length of a coastline can be calculated for a given purpose. Among these are:








Requirements on the level of detail
Sources to be used
Scale of the sources
Method to be used
Generalisation
What to be included (islands, inland waters, artificial structures…)
How far do we measure river mouths
Dynamic aspects and evolution of coastline
The CG identified some general requirements, specifications and guidance for those who may need to calculate the length of a coastline:




Have a common definition of what is used in calculations
Sufficient metadata should be associated with the calculated length. These include information
on the methods used, source data, purpose of the calculation, what is included in the calculation,
specifications used, expected use of the results
The calculated results should be repeatable
The results should be auditable
Coastline Length calculation for comparison purposes based on ENCs
The CG has developed a specification on a harmonised approach to define the length of a coastline for
comparison purposes, based on official, standardised and available data: S-57 Electronic Navigational
Charts (ENC).
The ENC coverage at Navigation Purpose code 1 (Overview), which is almost complete, is recommended
as the basis for the calculation. Where this coverage is not available or suited for comparison purposes,
Navigation Purpose code 2 or largest existing scales should be used. The key concept here is that the initial selection of equivalent scale products is fundamental to appropriately comparing lengths of coastline
between two or more States.
The CG noted the following benefits of using ENC as the basis for the calculations:






ENCs are officially produced under the authority of national Hydrographic Offices (HOs).
The coverage of small scale ENCs is effectively complete.
The ENC product specification does not allow overlaps in the same navigation purpose code –
hence a single unambiguous source of data should normally be available.
It is possible to identify the Producer State from the ENC data for each coastline segment.
Data is already in a consistent structure and in a uniform format and associated with a unique
geodetic datum
There are tools to extract coastlines from unencrypted ENC data sets.
The following specification identifies the sources to be used for the calculation, what elements should be
included and the metadata to be associated with the results. Appendix 1 provides examples of calculated
lengths together with relevant metadata.
Calculation details
1.
For the purposes of this method, the coastline is defined as the High Water Line as represented by
the Coastline, Shoreline Construction and Causeway object classes of the applicable Electronic
Navigation Charts (ENC).
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2.
The length of the coastline between two points is the sum of the lengths of the three Coastline,
Shoreline Construction and Causeway object classes between those points.
3.
Equivalent scale and vintage products are recommended for the calculation to support comparative
analysis. The following approaches are recommended:

The relevant lengths obtained from Navigation Purpose code 1 (overview) ENC cells should be
considered first for the calculation.

If Navigation Purpose code X ENC cells have not been published or are not suited for comparison purposes, data from Navigation Purpose code X+1 ENC cells (largest scales) should be
used.

In cases where data from Navigation Purpose code X ENC cells is supplemented by data from
Navigation Purpose code X+1 ENC cells, the latter is counted from the vertex closest to the last
vertex of the code X ENC corresponding curve (see Appendix 2).
4.
River mouths should be included in the calculation to the point where they become a line feature in
the ENC band that is used for the calculation. When the chart ends first or when there is no greatest ENC scale to complete the river, a straight line is drawn across the mouth and included in the
measurement of the length of coastline.
5.
Water bodies, such as inland lakes, which may be upstream of a river line should not be included in
the calculation of coastline (for example: in the case of inland water linked to the sea by a canal).
6.
The end of each State coastline will be at the agreed or declared border line.
Data and descriptive metadata
Whatever the way of calculation of the length of coastline, the results should at least include the following
metadata:




Country name
Two-letter Country code (IHO S-62)
Length
Unit of Measure (UoM)
Some metadata should be also included with the result of the calculation.
Note: elements marked * are repeatable.









Any comments
Point of contact of the organisation responsible for the calculation (such as the postal address or
web addresses of the HO)
Method of calculation (e.g. International Hydrographic Review reference)
Date of calculation (YYYY/mm/dd)
Identifier of the ENC cell(s) used for the calculation *
Edition date of the ENC(s) *
Producer code of the ENC(s) (IHO S-62) *
Scale of the line segment(s) used *
Object Classes included in the calculation *
Conclusions
France achieved some tests to validate this method and results are shown in Appendix 3. Now, it is up to
nations or interested readers to complete it.
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Biography of the Author
Laurent LOUVART
He is currently deputy director of research & innovation department, SHOM Headquarters. Amongst other
duties, he is responsible for managing the survey fleet renewal project and representing SHOM at the IHO’s
Hydrographic Services & Standards Committee (HSCC).
e-mail : [email protected]
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Appendix 1 - Examples of different calculations for the same State
This example is based on a quick web search. It illustrates the wide variation in the quoted lengths of the
coastline of Finland - from 1,100 km to 314,604 km, thus illustrating the need for a common metric and
minimum metadata.
Length [km]
1100
1250
What is included
Only sea border line.
Metadata
No metadata available
No metadata available
2774
Shoreline only.
4600
6299
Coastal shorelines.
Based on 1:4.5M.
No other metadata available
No metadata available
No metadata available
31119
No metadata available
39125
Basic topographic map
1:10.000.
No other metadata available
No metadata available
46198
314604
Coastal shorelines including shorelines of islands
and of lakes on islands.
Coastal shorelines and
shorelines of lakes including shorelines of islands
and of lakes on islands.
No metadata available
57
Source
Unspecified document
CIA World Fact book:
Worldwide list of lengths
of coastlines
Unspecified document
Unspecified document
Finnish Environmental
Centre
NGA World Vector
Shoreline
Unspecified document
Finnish Environmental
Centre
Finnish Environmental
Centre
INTERNATIONAL HYDROGRAPHIC REVIEW
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Appendix 2 - An Example of how incorporate rivers
using Navigation Purpose codes 1 and 2 ENC cells
Below is an illustrated example on how Navigation Purpose codes 1 and 2 ENC cells should be handled so
that the latter supplement the former.
Fig.1 : Navigation Purpose code 1 ENC (blue), classes Coastline, Shoreline construction and Causeway
The line presents a discontinuity that can be supplemented by Navigation Purpose code 2 ENC data (red).
The next figure displays the cropped area (dashed box).
Fig.2 : Crop on the discontinuity.Navigation Purpose code 1 data is supplemented by Navigation Purpose
code 2 data from the vertex closest to the last vertex of the code 1 ENC curve (arrows).
Fig.3 : Calculation can now be based on the composite coastline.
58
Note : Figures are not official. It was carried out as an illustration of the ENC based method.
Appendix 3 - Lengths of coastlines for comparison purposes
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INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
NEW SCIENTIFIC CONTRIBUTION
TO THE KING ABDULAZIZ UNIVERSITY
The King Abdulaziz University of Saudi Arabia is to be newly equipped with a new ultra
sophisticated vessel in the field of research and scientific exploitation.
This vessel, to be delivered early 2014, is a composite built by a French shipyard renowned
for this type of construction, appropriate for the conditions of the Red Sea, is specialised in
all maritime areas :
- Hydrography with latest generation of sonars : Multi-beam 3000m, single beam,
-
sidescan, SVP, subbottom profiler, GPS, DGPS, GPS RTK and other instruments and
softwares.
Oceanography
Marine Physics
Marine Biology
Fishing
Underwater Research with a ROV 1000m and the new GAPSS system
Navigation and communication
Meteorology
Archeology
The vessel is able to stay at sea for 25 days and able to be on scientific mission for 45 days
with 25 members on board, including both crew and scientists.
This new multipurpose vessel brings to completion the King Abdulaziz University scientific
shipping fleet, which already includes two 15m vessels, to broaden its scientific research
locally and internationally.
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INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
NOUVELLE CONTRIBUTION SCIENTIFIQUE
DE L’UNIVERSITE « KING ABDULAZIZ»
L’Université King Abdulaziz d’Arabie Saoudite va se doter d’un nouveau navire ultra sophistiqué dans le domaine de la recherche et de l’exploitation scientifique.
Ce navire qui sera livré début 2014, est un bâtiment en composite construit par un chantier
naval français expert dans ce type de construction, approprié aux conditions de la mer rouge
et specialisé dans tous les domains maritimes :
- Hydrographie avec les dernières générations de sonars : multifaisceaux 3000m,
-
monofaisceaux, à balayage latéral, SVP, profileurs sous-marin, GPS, DGPS, GPS
RTK et autres instruments et logiciels
Océanographie
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Recherche sous-marine avec engins télécommandés (ROV) à 1000m et le
nouveau système GAPSS
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Ce navire a la capacité de rester durant 25 jours en transit et 45 jours en mission scientifique
et peut accueillir à son bord 25 personnes incluant l’équipage et les scientifiques.
Ce nouveau navire polyvalent vient compléter la flotte scientifique de l’Université King
Abdulaziz déjà constituée de 2 navires de 15m, pour élargir ses recherches scientifiques
aussi bien localement qu’internationalement.
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INTERNATIONAL HYDROGRAPHIC REVIEW
MAY 2013
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