Finding my first benchmark.

[whitekn3]

Back around 1955-1960 my grandfather showed me a brass plate fixed to a concrete pillar that was near a fence corner on the family farm. Ten or 20 years ago I tried to find it again and could not. Someone said they thought a bulldozer clearing brush may have wiped it out.

 

I recently learned that some "benchmarks", and this was a true benchmark with an elevation inscribed on the top, had a marker buried "below plough depth" below the surface and they can be refound. I looked at an overlay of USGS markers on a google map and the marker was not shown at all.

 

Is there any practical way of locating the original marker? Did elevation benchmarks ever have a lower stone marker?

[Bill93]

Very few elevation marks have an underground backup disk. I've seen some MORC data sheets that had a rivet below the pipe the disk was on, but that was not common practice for either USGS or C&GS/NGS. Only triangulation stations typically had underground disk.

 

If your disk had an elevation stamped it was very likely USGS as C&GS/NGS did not stamp elevations as a regular practice. And only a small fraction of USGS disks were measured to the standards to get in the NGS data base.

 

So I am not optimistic for you but wish you luck.

 

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Edit: the locations of elevation marks were usually SCALED off a topo map, which might be good within a few yards where there were features on the map to compare to, but the the values were truncated (not rounded) to whole seconds of lat-lon. Thus you can figure that even if the disk was perfectly located on the map, you have up to 100 ft north and 75 ft of west of the coordinates to search.

 

The way to find bench marks from the data sheet is to go to the lat-lon coordinates and then put the GPS away. Get out the tape, and measure from the features listed in the to-reach instructions on the data sheet.

Edited September 25, 2016 by Bill93

[Z15]

Here is an NGS map to zero in on the location to see if any marks are in the database that fit...

 

NGS Explorer