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New Benchmarks


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My wife is just finishing up a book written by Clarence King, Mountaineering in the Sierra Nevada, (a book she can recommend for any Benchmarker's library) and it got me to thinking. Does the USGS put out new Benchmarks?


It seems with all the mishaps I read about the demise of Benchmarks, that eventually the U.S. will be denuded of them :blink:


The second part of my question: how often does GC.com update the Benchmark database?


Oh yeah, go ahead and Markwell me :o

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I don't know USGS but I do know that the Missouri DNR (our state geodetic survey agency) continues to place survey markers around here. They were active through the 1990s and I believe that I have seen some from the 2000s. (The newer ones are not in our GeoCaching database though, thus I don't actively search them out.) I have also stumbled on some disks placed by other agencies around St. Louis -- probably not submitted to NGS however.

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At this time, GC.com does not update its benchmark data base. The most recent update took place in the year 2000.


Replacement monumenting varies by state. The North Carolina Geodetic Survey sets many new benchmarks every year. These make it into the NGS data base within two to four years, and they carry a unique PID series ("DG----"). The NC Dept of Transportation also sets new marks. Most of these are not included in the NGS data base.


Although some new marks are set as replacements for marks which have been destroyed, I find that many are part of a current project. This could be advance work for a new lake, or a new highway. They might be associated with a new survey of a county or state boundary line (often done to resolve a dispute). You might also encounter "height modernization" projects which can include both new marks, as well as upgrades to older marks.


Numerically, new marks only partially offset those which have been destroyed. Does this mean we will someday run out of benchmarks to hunt? No, because someone still has to visit the site and determine if a mark has been destroyed.


But I often wonder if we will run out of easy benchmarks to hunt. :P



Edited by PFF
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USGS puts new marks in, but they are mostly related to their stream gauge network and are rarely submitted to NGS for inclusion in the National Spatial Reference System. NGS still puts marks in for certain projects. There is currently a major leveling program being conducted in Puerto Rico and we recently completed a series of level lines in the U.S. Virgin Islands. NGS also puts marks at airports and from time-to-time other special projects.

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The GC benchmark top level page says 126450 benchmarks have been recovered ...There are 736425 in the data base.


That's 17.2% reported, so there are a lot left to hunt. We know that some of those reports aren't accurate, so the percentage left for conscientious mark dusters is more than 83%.


The ones left tend to be the harder ones as we make progress, so we won't lack for challenges.


And we will still need to check on the ones we found to see if they are still there ten years later, although that won't be as much fun as finding them the first time.

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