Altimeter Watch Tutorial: Types Of Altimeter Watches
There are two methods 99% of altimeter watches use to calculate altitude - global positioning systems (GPS) or barometric pressure.
For those that own an altimeter watch that gives altitude based on GPS readouts, your altitude will be as accurate as the map datum the watch is using to generate altitude. We'll discuss why in a minute. The majority of altimeter watch owners have an altimeter watch that calculates altitude using barometric pressure. In the following paragraphs I'll discuss the difference between GPS and barometric pressure altimeter watches and give examples of each.
GPS altimeter watches use latitude and longitude coordinates to identify your position on the grid and read out an altitude. This data is delivered to the watch from the manufacturer satellite and usually is based on USGS datum. If you have a GPS enabled altimeter watch you never need to recalibrate your watch since the information being displayed comes from a satellite and not from "on ground" conditions. Examples of GPS enable altimeter watches include the Forerunner series from Garmin and the Suunto X10.
Almost every non-GPS altimeter watch on the market uses barometric pressure to determine altitude. The watch has a function in it's built in software that takes the barometric pressure and calculates altitude. Because of this, the altitude readout accuracy needs to be carefully scrutinized, particularly if the weather has changed significantly since you last calibrated your watch. Examples of barometric pressure altimeter watches are the High Gear Axis and the Suunto Core. As already discussed, barometric pressure altimeter watches are subject to the outdoor weather conditions and as such should be calibrated at regular intervals.
The price points on GPS and barometric pressure watches are varied, with GPS enabled altimeter watches generally being more expensive. An altimeter watch using barometric pressure (such as the HighGear Axis or Suunto Vector) can be found for as little as $100. The GPS enabled altimeter watches are generally more expensive, with an entry price of around $250.
