5x12 pentomino tiling

Ordnance Survey Benchmark


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
Date/Time Taken:2015-05-10 08:55:57
Exposure Time:1/30s
F Number:f/8
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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