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.
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)|
|Outer Hebrides (Stornoway 15 datum)||0.011|
|Isle of Man||0.030|