Sites of Special Scientific Interest Units (England)

asNeeded

All data is captured to the Ordnance Survey National Grid sometimes called the British National Grid. OS MasterMap Topographic Layer produced and supplied by Ordnance Survey from data at 1:1250, 1:2500 and 1:10000 surveying and mapping standards - is used as the primary source. Other sources acquired internally and from external suppliers - may include aerial imagery at resolutions ranging from 25cm to 2m, Ordnance Survey 1:10000 raster images, historical OS mapping, charts and chart data from UK Hydrographic Office and other sources, scanned images of paper designation mapping (mostly originally produced at 1:10560 or 1:10000 scales), GPS and other surveyed data, and absolute coordinates. The data was first captured against an August 2002 cut of OS MasterMap Topography. Natural England has successfully uploaded an up-to-date version of OS MasterMap Topographic Layer. However, we have not yet updated our designated data holding to this new version of MasterMap. This should occur in the near future, when we will simultaneously apply positional accuracy improvement (PAI) to our data.