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Find out about the accuracy of our data and surveying, base stations and coordinate transformers, and how these work with the national Global Positioning System (GPS) system.

Network accuracy

The standard errors of base stations are generally better than 0.008 m in plan and 0.020 m in height.

Coordinate transformer 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

Standard error statistics

Regional datumStandard error (m)
Great Britain0.008
Outer Hebrides (Stornoway 15 datum)0.011
Isle of Man0.030

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© Ordnance Survey 2016