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NGS not USGS! Whose markers are they really?

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First off I like the new benchmark searches! Great job in setting this up. On the homepage you state:

What is a benchmark?

Benchmarks, also called Survey control markers or disks, are disks (and other various items) that are permanenty affixed at locations all over the United States to help land surveying. The United States Geological Survey (USGS) maintains a database of these locations, though much of the data is outdated.


Just to clear up what seems to be a source of confusion - the benchmarks you have in this database are part of the geodetic control network maintained by the National Geodetic Survey (NGS). The USGS (US Geological Survey) is the mapping agency that happens to show a lot of the benchmark locations on there topo maps but that is about it. You should change your link on the benchmark home page to

National Geodetic Survey homepage.


There are lots of brass caps/disks/survey markers and the NGS ones are very precise and provide a geodetic control for mapping and surveying in this country. But you will find lots of others!


The US Army Corps of Engineers place lots of survey markers at their dams, dikes, flood control structures, etc. And the BLM and your county surveyor place them all over to reference land survey corners as part of the public land survey system. And your local highway department will have them along the highways, at major bridges, overpasses, etc. Explaining all this (better than I have!) in some sort of fact sheet would help with the confusion folks (see other threads already posted!) have whenever they find a survey marker that is not in your database!

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