Complex sentence: The Ordnance Survey of Great Britain (OSGB) produces a number of highly accurate maps based on survey data defined on the OSGB36 datum which, in turn, is based on the Airy 1830 reference ellipsoid with major and minor axes equal to 6377563.396m and 6356256.910m respectively.
Split into simpler sentences: The Ordnance Survey of Great Britain (OSGB) produces a number of highly accurate maps. The survey data is defined on the OSGB36 datum which is based on the Airy 1830 reference ellipsoid which has major and minor axes equal to 6377563.396m and 6356256.910m respectively.