A benchmark should be relatively permanent, which is why one is often set at a corner of a building, large boulder or some other location that will be there for a long time. If you were to work off a surveying post established by the U.S. Geological Survey, you would be working off a benchmark where the elevation is given in terms of elevation above sea level. In my part of the world, it means an elevation of approximately 1,100 feet above sea level. Obviously, we do not need to know how high above sea level we are to install a
