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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

OSTN02 now defines OSGB36 National Grid (in conjunction with the National GPS Network). In this respect OSTN02 can be considered error free (not including any GPS positional errors). The agreement between OSTN02 and the old triangulation network stations (down to 3rd order) is 0.1m rms (Great Britain only).

The standard error in height of OSGM02 for each regional vertical datum are included in the table below. This error budget is for OSGM02 only and does not include any GPS heighting errors

Standard error statistics

Regional datumStandard error (m)
Great Britain0.02
Outer Hebrides0.09
Isle of Man0.03
St. Kilda0.06

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