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MSchwiebert

Benchmark on older Quadrangle Map - but not in database

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The photo is from a portion of the Hamler (OH) quadrangle that I have.  My copy was photo revised in 1973 so I'd suspect that it's not current.  Notice the "733" BM called out. This one does not have a data sheet in the current NGS explorer.  Is there a way to tell when/why it "fell out" of the database of data sheets? I'd guess it was destroyed at some point between 1973 and 2006 (I printed out copies of the Datasheets available then for Henry Co.) but would like to know to be sure.

IMG_5715.jpg

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The one marked BM 733 is likely a US Geological Survey disk, that may or may not still be there. I would guess it was never in the C&GS now NGS data base, because it is just a mile+ off of the D 17, E 17, F 17 line that goes north-south.  USGS put in a lot of marks to help with the mapping work but most of them aren't in the NGS data base.  It could also be some other semi-permanent feature instead of a disk, such as a chiseled mark on a culvert.

Edited by Bill93

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