ITM – GPS Compatible Mapping
ITM - Irish Transverse Mercator
A ‘GPS’ Compatible Reference System
Survey Ireland 2007
ITM Tutorial
Colin Bray, Ordnance Survey Ireland
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
ITM
• What is ITM?
• Why was ITM developed?
• Irish Grid / ITM comparison
• ITM lineage
• Benefits of ITM
• Implementation Issues
• Transformation utilities
• How can OSi help implementation
• Questions & answers
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
What is ITM ?
ITM is a GPS compatible mapping system that takes advantage of the
accuracy of GPS whilst minimising mapping distortions
–
GPS compatible (no transformations required)
–
Takes advantage of the accuracy of ETRF89
–
Minimises mapping distortions
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Why was ITM developed?
• Extensive use of GPS in geomatics
• Need for geometric interoperability (GPS & geographic data)
• International compatibility
• Shortcomings of the ‘Irish Grid’
–
–
–
–
Legacy distortion issues
Not GPS compatible
Dependant on transformation relationship to GPS
Can only realise IG to better than 1m using GPS
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Mapping System Parameters
Reference Ellipsoid
Central Meridian
Scale on CM
True Origin
False Origin
ø
λ
IG
ITM
Airy (modified)
GRS80
8° West
8° West
1.000 035
0.999 820
53° 30' North
8° West
53° 30' North
8° West
200 000 W
250 000 S
600 000 West
750 000 South
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Irish Grid & ITM Comparison
‘Irish Grid’ Mapsheet
‘ITM’ Mapsheet
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
ITM & Irish Grid
• 400,000 / 500,000 coordinate
difference
• Relationship defined via official
OSi / OSNI polynomial
transformation
– between ETRF89 and Ireland
1975 (accuracy better than 1m
everywhere in Ireland)
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Development of ITM
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
ITM Lineage
• 1999
– Concept introduced at ‘Survey Ireland 1999’ conference
• 2000
– Preliminary user information circulated
• 2001
– Consultation paper circulated
• 2001
– ITM Seminar road show (Cork, Belfast, Dublin, Galway)
• 2001
– ITM parameters formally adopted at ‘Survey Ireland 2001’
• 2002
– OSi converts production flowlines to ITM
• 2002/3 – ITM Technical Working Group
• 2002
– ‘Grid InQuest’ transformation utility available
• 2002
– On-line transformation utility available on OSi website
• 2003/7 – ITM presentations at various user groups / conferences
• 2004
– Irish Institution of Surveyors (IIS) recommends ITM adoption
• 2005
– Land Registry goes digital with ITM
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
ITM Consultation Process
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
IIS Recommends Adoption of ITM to Surveyors
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
What are the benefits of ITM?
• A more accurate coordinate reference system
– with the realisation of ETRF89 (IRENET95)
• Geometric interoperability between mapping and modern surveying
instrumentation
– Relationship not dependent on transformations
• Mapping distortions are minimised
• International compatibility
• Consistent standard / framework for relating geographic information
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Implementation Issues
• Accessing ITM data
• Viewing ITM data
• Converting between Irish Grid and ITM
• Relating ITM to legacy Irish Grid paper records
• Implementation phases
– Maintain existing Irish Grid geographic records and output
in ITM format when required
– Fully implement ITM across all systems and data
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
ITM Technical Working Group (TWG)
Members
• BKS Surveys
• Land Registry Ireland
• Bord Gais
• Land registry Northern Ireland
• Cork City Council
• LGCSB
• Electricity Supply Board
• NTL Northern Ireland
• ESBI Computing
• Ordnance Survey Ireland
• European Air Surveys
• Ordnance Survey of Northern Ireland
• GPS Surveys
• Proteus Solutions
• Irish Institution of Surveyors
• Translink
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
ITM TWG
Key Issues
• Data migration
• Grid / sheet indexing
• Legal issues
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Data Migration
Key Issues for consideration
• User education
• Software (vendor products)
• Application developers
• OSi / OSNI datasets
• Raster maps and aerial photography
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Grid Indexing
• The ITM TWG recommended a grid index referencing system based
on a 1km x 1km grid to be associated with the ITM mapping system
• ITM grid coordinate dimensions:
– Min
– Max
400,000.000 Easting (m)
800,000.000
“
500,000.000 Northing (m)
999,000.000
“
• Therefore a 1km x 1km grid index reference system would require a
6-digit numeric to uniquely refer to a specific 1km x 1km grid location
(bottom left hand corner)
• Example:
– ITM grid coordinate reference =
Survey Ireland 2007, Malahide
600,850
15th May 2007
ITM – GPS Compatible Mapping
Legal Issues
• The only precedent to this situation was the migration of data
from the Cassini projection to Irish Grid in the 1960’s
• There is no evidence of any legal issues arising from that
transition. As none of the TWG members enquires have
identified potential legal difficulties, it was concluded that, at this
point in time, there are no obvious legal impediments to the
introduction and use of ITM.
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Data Migration
• The main issue affecting successful migration to ITM is project
management. The basic migration process is well defined, but
requires detailed planning, control and quality assurance.
• If properly planned and managed, the migration to ITM will be
equivalent to a complete update of existing third party data, and a
new release of software.
• With proper planning, migration to ITM can be achieved within the
normal timescales for new releases of software and base datasets
• The involvement of the software application providers and the
software developers is key to successful migration
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Transformation Utilities
Currently available
• Interactive coordinate conversion on OSi website www.osi.ie
• Down loadable coordinate converter shareware from OSi
website www.osi.ie
Required
• All major GIS software vendors to implement polynomial
transformation
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
How can OSi help with implementation
• Providing software application providers and software developers
with the required software (DLL & developers manual) to facilitate the
implementation of data conversion at the user application end
• Setting up a software application provider / software developer user
group to progress their implementation of file conversion utilities
• Facilitating dual supply of ITM & Irish Grid during transitional phase
• Developing a shareware look-up utility that will enable users to easily
relate the 1:5,000 sheet index to ITM
Survey Ireland 2007, Malahide
15th May 2007
ITM – GPS Compatible Mapping
Thank you for your attention
Survey Ireland 2007, Malahide
15th May 2007