# The future of British mapping coordinate systems

As discussed in [Ordnance Datum Newlyn](https://docs.os.uk/more-than-maps/a-guide-to-coordinate-systems-in-great-britain/ordnance-survey-coordinate-systems/ordnance-datum-newlyn), ODNis the national height datum used across mainland Great Britain. There are, however, a number of other British height datums that are used on the surrounding islands. The main ones being; *Lerwick* on the Shetland Islands, *Stornoway* on the Outer Hebrides, *Douglas* on the Isle of Man and *St. Marys* on the Scilly Isles. All of these height datums are incorporated within the National Geoid Model OSGM15.