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OSTN15 and OSGM15 for developers

See our developer pack to incorporate OSTN15 transformation and OSGM15 geoid models into your software.

Our developer pack and Grid InQuestII software contain the polynomial transformation and OSGM15 geoid models for use in Ireland and Northern Ireland.

OSTN15/OSGM15 replaced the previous models OSTN02/OSGM02 in August 2016. There are several ways these models can be incorporated into your software.

Everything you need – OSTN15/OSGM15 for developers

  • Developer pack (13MB) – use the raw dataset from the developer pack. This includes the grid of transformation parameters, the procedures/equations to use, a worked example and some sample files for testing. Technical information is also included.
  • NTv2 format files (28MB) – NTv2 is popular with many GIS systems. The zip archive contains both text and binary NTv2 format files for OSTN15, sample files for testing and a user guide.
  • OSGM15 GTX format (2MB) - OSGM15 geoid model data in GTX format.
  • Grid InQuestII software – the Grid InQuestII software application contains DLLs and tools to enable the use of OSTN15 and OSGM15 with other software and web applications.
  • Grid InQuestII source code – the source code for Grid InQuestII is available for re-use and modification.
  • OSTN15_OSGM15 Lite Developer pack (70KB) – A reduced density version of OSTN15 and OSGM15 on a 20km grid. Lower accuracy (0.08m horizontal RMS tested against full version) from a much more compact parameter set.

Read our guide to coordinate systems in Great Britain (PDF) for important background information relating to OSTN15 and OSGM15. Further background information on the collection of the transformation data set and creation of the model was published in a comprehensive paper in Survey Review. The paper was for OSTN02 but applies equally to OSTN15.

This software is licensed as per the terms of the BSD Licence.


OSTN15/OSGM15 replaced the previous models of OSTN02/OSGM02 in August 2016. There are resources available to help you with OSTN02/OSGM02: