Setting Up in the Real World – UK Coordinate Systems

Update - November 2016: Ordnance Survey recently published OSTN15, "the new geoid for Britain". We are working towards making this available. This blog will be updated once we have done so.

UK users creating new data should always use the OSGB-GPS-2002 GCS when working with the UK National Grid  to ensure that when converted to ETRS89 or WGS84 based datums, projection coordinates are the most accurate possible.

The other British National Grids included in our libraries are used to import older data that was created prior to the introduction of OSGB-GPS-2002.

Some long running infrastructure projects may have particular specifications that overrides this advice. Where project specifications for geo-referencing exist always use them to be consistent with other project participants!

How to access OSGB-GPS-2002

When you open the GCS Library in MicroStation or AECOsim Building Designer you won't find OSGB-GPS-2002.

To make it available download OSGB-GPS-2002 Grid Shift File and extract OSTN02.txt to the appropriate location:

  • MicroStation V8i: C:\Program Files (x86)\Bentley\MicroStation V8i (SELECTseries)\MicroStation\GeoCoordinateData
  • MicroStation CONNECT Edition: C:\Program Files\Bentley\MicroStation CONNECT Edition\MicroStation\GeoCoordinateData
  • AECOsim Building Designer V8i: C:\Program Files (x86)\Bentley\AECOsimBuildingDesigner V8i Ss6\AECOsimBuildingDesigner\GeoCoordinateData

Note: As updating to AECOsim Building Designer SS6 Update 1 is an install over process if you added this file in SS6 it will still be in place after the upgrade.

This will need to be done for every machine that requires this GCS. It will then be listed as shown:


If compatibility with this coordinate system is needed please download the OSGB-GPS-1997 Grid Shift File. It should be installed using the method described above.

Also see

Setting Up in the Real World – GeoReferencing