What To Look For
Altimeters are excellent outdoor tools that can provide useful and interesting information. All altimeters provide a reading of your altitude, but a couple of distinguishing characteristics separate different models. Altimeters can come as standalone units or as a feature on digital devices like GPS units and sports watches. Though most altimeters are digital, there are a number of analog altimeters on the market. One helpful feature found on more expensive altimeters is temperature compensation, which keeps the unit unaffected by changes in temperature that limit the accuracy of lesser altimeters. These altimeters can be transferred from your pocket to the outside air without experiencing any loss in accuracy. Another thing to be aware of when shopping for an altimeter is the maximum altitude provided, which can vary from model to model.
Even though you may never scale Everest, it doesn't hurt to purchase an altimeter that displays up to its peak height (29,035 feet). In the same vein, the lowest land point on Earth is at the Dead Sea at -1371 feet, so get an altimeter that covers the full range. This way you know the altimeter is capable of displaying any possible altitude you'll need in the outdoors. The lower the increments used (altimeter resolution) to display your altitude (20 feet, 10 feet) the better, since larger increments won't really allow you to hone in on your position as effectively. Consider something that uses a resolution of 5 feet or less. Finally, consider what else the device can do with the information provided by the altimeter. Many sports watches use altimeter-based readings to provide additional details like total vertical gained and vertical ascent/descent rate. If you're looking to track your stats, consider a device that offers these features. Sufficient memory to hold data from multiple trips or runs may also be useful to you.
Common Pitfalls
Altimeters are quite useful in providing your elevation at any given moment and statistics like vertical gain. They can also be excellent navigational tools in allowing you to pinpoint your exact location on a topographic map, based upon the elevation contours of the map. However, barometric altimeters are not completely accurate and are affected by weather. Since the altimeter relies on air pressure to measure altitude gain, pressure increases or decreases brought on by changing weather can also change the reading of your altimeter, making it less accurate. You will want to calibrate the device often and depending upon your usage, it may be an unnecessary device. Further, it may not be wise to purchase an expensive altimeter for hundreds of dollars when you'll have to check its accuracy against a topographic map anyway.
Where To Buy
Altimeters can be purchased at any quality outdoor sports store. For the best selection, larger retailers like Backcountry and REI are good places to start. If you're looking for an analog altimeter, you can find a good selection online at the Altimeter Store. A local outdoor sports shop would also be a good option to try the altimeter in person.
Cost
The cost of altimeters varies greatly based upon the specific device and additional features offered. Sports watches that include altimeters begin around $150 and run upwards of $600 for advanced GPS and performance software systems. Standalone altimeters can be found for as low as $50 for basic, analog models. More accurate, high-end models will run up to $500. Standalone digital models start at around $125.
Comparison Shopping
GPS units may provide altitude in two separate ways: all units can use GPS satellites to calculate elevation and some also use a barometer to measure air pressure change. The latter is comparable to other altimeters used in sports watches or sold alone. Barometric pressure is a more accurate way to measure altitude; look for a GPS that includes a barometric altimeter as well as a GPS-based one. Digital altimeters generally offer lower increments allowing you to better hone in on your altitude than do analog altimeters. Digital altimeters also usually measure the full range between -1371 and 29,035 feet, if not greater, whereas analog altimeters may not.
