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).
Now, I don't go out looking for benchmarks like I go out hunting for caches. However, if the cache description tells me there is a near by benchmark, or I happen to come across one - I will make the find.
Ironically, I have found 4 benchmarks in the last week. All of them happened to be right near caches. It is typical, but not mandatory, for the "finder" to upload a picture of their GPS by the Benchmark. Here is what many of the pictures end up looking like:
Some benchmarks will also have a Witness Post.
Here is one Witness Post that has seen better days.
I've only found 6 bench marks, so I can't give your a very detailed lesson, but I can point you in the right direction. You can learn more about benchmarks and benchmarking here.
If you are not a Geocacher - I hope I've at least introduced you to something new!
If you are a Geocacher I'd like to know... have you gotten a benchmark before? Do you only get them while caching, or do you seek them out even if there is not a cache near by?
What is Geocaching? Answer here.