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Ordnance Survey Benchmark

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You may have seen one of these before on your travels. This is the one on All Saints' church here in Milton. It's an Ordnance Survey benchmark, a type called a "cut mark" one, i.e. it's carved into the stone. If you look it up in their database it's 7.646m above sea level and 1.1m above the ground and it's a secondary mark. Last levelled in 1971. Verified in 1984.

Having read up on this then if I understand the maths correctly the nearest "fundamental benchmark", which is considered error free, is at Wicken, which is 11.35km away and hence the error on this benchmark1 is:

±5mm × √11.35 = ±17mm

Uh huh. I'll bear that in mind when I'm trying to keep my nose out of the water.

  1. As it's a secondary, it would ±2mm if it was a Geodetic and ±12mm if it was a Tertiary.

Tags: Milton, photos Written 10/05/15
File Name:20150510_085557_02824.jpg
File Size:7264KB
Make:SONY
Model:NEX-6
Date/Time Taken:2015-05-10 08:55:57
Exposure Time:1/30s
F Number:f/8
ISO:200
Focal Length:unknown
Focal Length In 35mm Film:
Lens Model:Minolta MD Zoom 35-70mm MDIII
Location:0° 9' 58.67" E,   52° 14' 39.11" N

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