The plane grid form of OSTN02 is not easily compatible with some GIS systems. So a transformation data format known as NTv2 is used.
In its original form, OSTN02 consists of a plane 700km by 1250km grid of 1km resolution with an eastings and northing shift at each grid node.
NTv2 format is a gridded format but the grid is realised on a latitude/longitude graticule and the shifts are expressed as differences in latitude and longitude.
You can access the Defence Geographic Centre (DGC) conversion of the plane grid version of OSTN02 to NTv2. The difference in transformed coordinates between the original OSTN02 format and the NTv2 format is insignificant (0.001m on average, 0.01m maximum).
The 10km off shore buffer is retained in the NTv2 version of OSTN02 so users must be aware that no transformation will take place beyond this limit. Unlike in a dedicated implementation of the original OSTN02 grid, a GIS system using the NTv2 version of OSTN02 is unlikely to warn the user that coordinates are outside the 10km boundary, and will therefore not be transformed.
The data file
The zipped archive contains a text version (.txt) and a binary version (.gsb) of the OSTN02_NTv2 data file. There is also a text file of the NTv2 header information. Ordnance Survey and Defence Geographics Centre cannot provide guidance on how to install OSTN02_NTv2 into GIS systems. Please contact your GIS system vendor for help with this.
We recommend you test the transformation once installed.
Data copyright and other intellectual property rights
The OSTN02 data has been created by Ordnance Survey Great Britain and it has been converted into the NTv2 format by the Defence Geographics Centre (part of the Ministry of Defence).
The copyright and database rights in OSTN02 data in NTv2 format are therefore owned by the Crown.
The OSTN02 data in NTv2 format is licensed to users pursuant to the terms of the Open Source Initiative BSD Licence.
The copyright notice which must be attached to the software under the terms of the BSD licence is as follows:
© Crown copyright, Ordnance Survey and the Ministry of Defence (MOD) 2002. All rights reserved.
The OSTN02 data in NTv2 format is provided ‘as is’ and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. In no event shall Ordnance Survey or the Ministry of Defence be liable for any direct, indirect, incidental, special, exemplary or consequential damages (including but not limited to procurement of substitute goods or services, loss of use, data or profits, or business interruption) however caused and on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of the OSTN02 data in NTv2 format.