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USGS quad says "BM", but no datasheet?


phil_langlois
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There are lots of survey marks on the land, only a fraction of which are in the NGS database. Could it be one placed by a state or local agency? Having said that, I would have thought that given the limited number of BM designations on topo maps, that they would likely be ones in the NGS database. But maybe not.

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I've often wondered about that too.

Is there a database somewhere of the BM's that show up on the topo maps? They must be cataloged somewhere?! Some of the maps around here have a number next to the triangle and the "BM" label...don't know if that's altitude or some kind of a reference number.

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on military maps, benchmarks are indicated by the - BM - symbol. Non-monumented benchmarks are indicated with just the - BM - ,while monumented benchmarks have an - X - with the - BM -. The number following the BMx is the elevation in meters. So for example...

 

A monumented benchmard 1234 meters asl would be:

 

BMx1234

 

and a non-monumented benchmark 963 meters asl would be:

 

BM 963

 

hope it helps.

 

Mike. KD9KC.

El Paso, Texas.

 

Seventeen minutes after her FIRST call for help, police officers arrived to find Ronyale White dead.

 

Prohibiting self defense is the ultimate crime. Police carry guns to protect themselves. What protects YOU ???

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