Pylon is a Greek word that means "gateway," from pyle, "gate or entrance."
To find the height of a specific pylon. stand on the same level as the pylon, use something to look at exactly 45 degrees. then move backwards or fowards untill the top of the pylon is in line with your line of sight.
This is a quick geo cache and very easy to spot in an open area where Pylons run through.
Hope you enjoy the cache.