Whenever I talk about grabbing a benchmark I here “They are not worth a smiley.” That is usually the ends of it so I have given up unless you need some for a challenge cache GC3HV14. A lot of them seem to be on private land around me. I have placed a couple on Waymarking.com and have never had a find. I placed a cache at one and still nobody has marked it. GC5D0FY That is a poor explanation.

What is a benchmark?
A benchmark is a point whose position is known to a high degree of accuracy and is normally marked in some way. The marker is often a metal disk made for this purpose, but it can also be a church spire, a radio tower, a mark chiseled into stone, or a metal rod driven into the ground. Over two centuries or so, many other objects of greater or lesser permanence have been used. Benchmarks can be found at various locations all over the United States. They are used by land surveyors, builders and engineers, map makers, and other professionals who need an accurate answer to the question, “Where?” Many of these markers are part of the geodetic control network (technically known as the National Spatial Reference System, or NSRS) created and maintained by NOAA’s National Geodetic Survey (NGS).

Why search for benchmarks?
The interesting thing about benchmarks is that a majority of them are located in plain sight (though largely ignored by the general public). Searching out these locations and documenting them allows others to share pictures of the various areas where they are placed. There’s a certain excitement to be the first to find and document a control point, as well as seeing what others have found through photos on the website’s benchmark gallery. Some of these points haven’t been visited and documented in a very long time, so you may also be rediscovering long neglected objects of American history as well! :w

More info at http://www.geocaching.com/mark/#Whatis