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Hemel Hempstead: High Street Green Triangulation Pillar

Now rather incongruously sited in the grass verge on the east side of High Street Green and surrounded by houses and trees, this survey triangulation pillar, which was originally surveyed in 1948, served its purpose before and during the development of Hemel Hempstead after the Second World War. Its published co-ordinates are Easting 507237.625, Northing 208316.031, but these have not been realised through the current ETRS89 (European Terrestrial Reference System 1989) and OSTN02 transformation parameters, so the OS would not consider them now to be the true co-ordinates. The height of the reference mark on the flush bracket on the side of the pillar is 148.556 metres above sea level.