Accuracy of OS Net, OSTN15 and OSGM15

Find out about the accuracy of our OS Net stations and coordinate transformations.

OS Net station coordinate accuracy

The standard errors of OS Net base station coordinates are generally better than 0.008 m in plan and 0.020 m in height.

Download OS Net data

OSTN15/OSGM15 transformation accuracy

OSTN15 now defines OSGB36 National Grid (in conjunction with the OS Net stations). In this respect OSTN15 can be considered error free (not including any GNSS positional errors). The agreement between OSTN15 and the old triangulation network stations (down to 3rd order) is 0.1m rms (Great Britain only).

The standard error in height of OSGM15 for each regional vertical datum are included in the table below. This error budget is for OSGM15 only and does not include any GNSS heighting errors

Regional height datum Standard error (m)
Great Britain 0.008
Orkney 0.017
Shetland 0.018
Outer Hebrides (Stornoway 15 datum) 0.011
Isle of Man 0.030

Use our online OSTN15-OSGM15 transformation tool

Download Grid InQuest2 software, incorporating OSTN15 and OSGM15

Download OSTN15 and OSGM15 raw data files


Accuracy information for legacy data sets