Beacon: In Surveying and Benchmark hunting, there might be several meaning for the term beacon. Here are several. There might be more:
Airway Beacon: When early aircarft began to fly longer distances than down the road to the next town, there were no aids to help pilots find their way around. Pilots essentially flew by looking out of the window at the ground, and sometimes used whatever maps they could find (such as automobile road maps). This was OK for daytime, but airmail pilots flew at night also. Some pilots (and their friends on the ground!) began using bonfires , which became the first artificial "beacons" for night navigation. By about 1923, ideas were tried like lighted airport boundaries, spot-lit windsocks and signs, etc. To support airmail flying, the Post Office worked to complete a transcontinental airway of beacons on towers spaced 15 to 25 miles apart, each with enough brightness to be seen for 40 miles in clear weather. Each tower had site numbers painted on it for daytime identification. At night, the beacons flashed in a certain sequence so that pilots could match their location to the printed guide that they carried. One fixed tower light pointed to the next field and one to the previous tower, forming an aerial roadway. After World War II, these airway Beacons were eventually replaced by various radio (electronic) navigation systems, such as "A-N" airways, Non-Directional Beacons (NDB), VOR, and eventually GPS!
Obviously, Airway Beacon sites had to be accurately located, and so their locations were surveyed. Although most Airway Beacons have been torn down (or allowed to fall down!), there are a few still standing, and there are efforts to save the remaining ones. The NGS still contains a number of Airway Beacons, and they are fun to find! An example of one is