UNIVERSITY OF KWAZULU-NATAL
EXAMINATIONS: JUNE 2014
ENSV2HY
HYDROGRAPHIC SURVEYING
DURATION: 3 HOURS
BSc (Surv)
TOTAL MARKS: 100
INTERNAL EXAMINER:
Mr J. Jackson
EXTERNAL EXAMINER:
Mr. A. Forbes
INSTRUCTIONS:
1. MAKE SURE YOU READ ALL INSTRUCTIONS AND THE NOTES VERY CAREFULLY,
BEFORE ATTEMPTING THE QUESTIONS.
2. READ THE QUESTIONS CAREFULLY BEFORE ANSWERING.
3. PLEASE WRITE ANSWERS IN YOUR OWN WORDS
4. UNTIDY WORK WILL BE PENALISED, PLEASE WRITE CLEARLY.
5. PLEASE WRITE YOUR ANSWERS FULLY BECAUSE MARKS WILL BE GIVEN FOR
METHOD.
IMPORTANT NOTES:
1. THIS IS AN OPEN BOOK EXAM
2. This exam counts 70% towards the final mark for this module
3. The use of programmable calculators is permitted.
University of KwaZulu-Natal
EXAMINATIONS
HYDROGRAPHIC SURVEYING
June 2014
ENSV2HY
QUESTION 1 The physics of the oceans [20 Marks]
(a) Draw a sketch profile of the seabed, showing the following: The continental shelf, the
continental slope, , the abyssal plain ,the continental rise
(4)
(b) What is a typical depth for the continental shelf, the abyssal plain and an ocean trench?
(3)
(c) Where do you find most ocean trenches and what processes create them? Explain why
you should not expect to find a continental rise near an ocean trench.
(3)
(d) Explain why there is no ocean trench near South Africa.
(5)
(e) Explain why most hydrographic surveys are carried out on the continental shelf rather
than the abyss
(5)
[20]
QUESTION 2 Positioning Depth Determination [20 Marks]
(a)
Explain the relationship between the Order of a survey and a Zone of Confidence.
(2)
(b)
Give an example of data collected on an “opportunity” basis. What would be a typical
ZOC for a chart based on such data?
(2)
(c)
The red curved lines in the map below show where flight MH370 could have been
when it sent messages to IMMARSAT. (i) What is the name hydrographic surveyors
use for such a line? (ii) What do they call where three such lines cross? (iii) What do
land surveyors call the similar graphic they use?
(6)
(d)
Explain why it is sensible for the hydrographic surveyor to use LAT as chart datum,
and why it is sensible for the land surveyor to use MSL.
(4)
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University of KwaZulu-Natal
EXAMINATIONS
HYDROGRAPHIC SURVEYING
June 2014
ENSV2HY
Question 2 (continued)
(e)
Land surveyors almost always use carrier-phase GNSS but hydrographic surveyors
usually use code phase GNSS for positioning. Explain why.
(3)
(f)
Classify each of the following devices as transmitters, receivers or dual function:
Hydrophone, pinger, transducer, transponder, acoustic beacon
(3)
[20]
QUESTION 3 Depth measurement, feature detection.
(a)
Suppose a sound beam is projected from the surface downwards at a nadir angle of
about 60 degrees. Using Snell’s law of refraction and the typical sound velocity profile
shown below, draw a sketch showing the features of the beam direction down to a
depth of 5.5km. Annotate your sketch to explain what you are trying to show
(6)
(b)
Suppose two hydrophones are 0.10m apart, on the hull of the vessel. H2 receives a
return signal 0.05 milliseconds after H1. If c=1500m/s what is the nadir angle to the
beacon?
(5)
(c)
For a ZOC A2 inshore survey chart in depth 30m at a scale 1:25000 what should be
the line spacing and the sonar range scale?
(3)
(d)
Suppose you need to detect an object 2.2m long by guaranteeing 5 pings in the near
field at a slant range of 15m. The ping interval is 0.2 seconds. If the beam width is
1.5 degrees, what should be your speed of advance?
(6)
[20]
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University of KwaZulu-Natal
EXAMINATIONS
HYDROGRAPHIC SURVEYING
June 2014
ENSV2HY
QUESTION 4 Water Levels and Tides [20 Marks]
(a)
What do the terms “Lower High Water” and “Higher High Water”mean?
(3)\
(b)
What do the terms “Spring tide” and “Neap tide” mean?
(3)
(c)
Explain how “perigee and perihelion, apogee and aphelion” affect the strength of the
tides.
(3)
(d)
Why could it be important for a ship navigator to know the times of flow tide, ebb
tide and slack water?
(3)
(e)
Suppose you are to do a survey in a channel far from a standard port. Explain what
equipment would you need to correct depth measurements to chart datum, where
would you deploy this equipment and how would you use the measurements.
(6)
(f)
When rescue aircraft first found floating debris they thought could have come from
MH370, they deployed buoys fitted with GPS to track the current movement. Were
these Eulerian or Lagrangian type current meters?
(2)
[20]
QUESTION 5 Maritime Boundaries [20 Marks]
(a)
The term “baseline” can mean several different things in different surveying contexts.
Explain what it means in the context of maritime boundaries and explain what it
means in one other surveying context.
(5)
(b)
Explain how the power of the state is limited in each of these:
1) Territorial Waters
2) Contiguous Zone
3) Exclusive Economic Zone
4) High Seas
5) Internal Waters
(c)
(10)
Describe how the rights and obligations of authorities are defined by the following:
Air Defence Identification Zones, Flight Information Regions, Volcanic Ash Advisory
Centres, Maritime Search and rescue Regions.
(5)
[20]
[TOTAL 100]
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