XKCD has a fun comic about a guy who recalculates the world records of pole vaulters based on the gravity of the locations of various events. Earth's surface g

XKCD has a fun comic about a guy who recalculates the world records of pole vaulters based on the gravity of the locations of various events. Earth's surface gravity is by no means constant -- it varies, presumably due to the density and altitude of any particular location. Indeed, "sea level" is defined as the level that the sea would be at, if the area of question didn't have the land mass, but still had the same gravity. Of the various possibilities, this particular definition is useful, in that it you can expect the air pressure at a particular altitude to be the same, regardless of where you are, after factoring in things like temperature and humidity -- which is kindof important if you're a pilot of some sort!