These days (and probably forever going forward) altimeter watches either use GPS or barometric pressure to figure out your altitude.

Barometric pressure altimeter watches, as their name implies, use air pressure to determine elevation. Most altimeter watches are barometric altimeter watches, because the technology is self contained and does not depend on communication with any external source. GPS altimeter watches communicate geographic position with a satellite in the earth's atmosphere and return altitude based on map datum. A GPS enabled altimeter watch does not need to be re-calibrated and is generally more accurate than a barometric pressure altimeter watch.

If your altimeter watch is GPS enabled, the way it calculates altitude is by sending your latitude and longitude to a satellite, which likely communicates with the manufacturer and returns your altitude, among a number of other data points. Because of this GPS altimeter watches are considered to be more accurate that their barometric watch counterparts. Not having to recalibrate is one of the obvious benefits to owning a GPS enabled altimeter watch. However, one of the downsides is your position and altitude is often subject to terrain - on flat, open terrain you will have near perfect communication with the satellite. However, in mountainous terrain, particularly in a canyon or gorge, you will often have poor satellite signal, resulting in inaccurate latitude and longitude positioning. Obviously, this results in somewhat questionable accuracy of your elevation. Examples of GPS enable altimeter watches are the Forerunner 305 or the Suunto X10.

Most altimeter watches using barometric pressure have a built in software component that uses the watch barometer to calculate altitude. While the exact function that the watch uses to determine altitude is beyond the scope of this article, it is important to remember that barometric pressure changes rapidly as weather changes. Because of this, during outdoor activity it is important to use known positions to calculate altitude and recalibrate your watch if necessary. While there are literally hundreds of watches out there using barometric pressure to calculate altitude, some of the more popular brands are HighGear, St.Moritz, and Suunto.

Now that we have reviewed how GPS and barometric pressure altimeter watches function - the obvious next question is cost. While the price points for altimeter watches are varied, generally GPS enabled altimeter watches are more expensive that barometric pressure watches. That said, it is not as simple as either GPS or barometric pressure to determine cost. Manufacturing quality, feature set, and brand also can influence the price point.

Learn more about the types of Altimeter Watches. Stop by Anthony Edward's site where you can find out all about the best altimeter watch for your needs.