Monday, November 09, 2009

emapsite: Benchmark Layers to OS MasterMap data

Surveyors in Great Britain are using emapsite to continue to access the locations and heights of traditional benchmarks despite their removal from the latest Ordnance Survey digital map data. emapsite has reintroduced benchmarks as an additional layer in the latest OS MasterMap data which can be viewed online in emapsite’s Plans Ahead mapping service.

Benchmarks were the mainstay of traditional survey control information in Great Britain until the growth of GPS. They record height above Ordnance Datum and are most commonly found on buildings or other semi-permanent features. Nearly 200 ‘fundamental’ bench marks were built and maintained, establishing more than 500,000 ‘lower order’ marks for measurement purposes over several decades.

As it was not economically viable to continue maintaining the physical network given the move to GPS, Ordnance Survey eventually began removing benchmark information from the updates to its large-scale OS MasterMap Topography Layer dataset in summer 2009.


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