All our data is supplied in OSGB'36 British National Grid, with elevations recorded above Ordnance Datum Newlyn (AODN).
Our current (2017) composite is transformed to the OSTN'02 geoid model.
The Ordnance Survey geoid models have updated over time as they have become more sophisticated. We have always used the latest models available at the time of survey. For time stamped data and point cloud data please refer to the metadata catalogues for the specific geoid model used for a survey. For all surveys carried out post 26th August 2016 we have used the latest (OSGM'15) geoid model.