Bench Mark 2646 - Oswestry, St Oswald's Church SJ 28849 29351

An Ordinanace Survey Benchmark on the wall of the church. Benchmarks were fixed points which were used in the past to calculate a height above the mean sea level.

Today, access to the national height reference is through the OS Net permanent GPS stations, The advantage of using this method is that anyone with accurate GPS can access the height system anywhere. Also with old bench marks, particularly in mining areas where subsidence occurs, the readings can be wildly inaccurate.