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The Great War (1914-1918) Forum

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Trench map BM codes?


Hull17KSLI

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Just a question on what the B.M codes stand for on the trench maps. I've been looking at a few and then numbers show some form of order but i'm unsure what they mean.

The ones I can see are B.M.151.7 and B.M.151.8

 

Thanks

Hull

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I believe it stands for bench mark or benchmark; a known, permanent, and marked survey height above sea level. You will notice on the map that the figures after the B.M. are very close to the value of near height contours shown, e.g. 151.7 will (I hope) show a contour line of 150 (metres above sea level) nearby.  

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Very far off what I was thinking, but makes far more sense. Thanks for clearing it up for me!

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