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An altimeter is a type of barometer that measures altitude by detecting changes in atmospheric pressure. An analog altimeter shows changes in elevation using a compass-style needle, whereas a digital altimeter displays electronic numbers on a screen. Digital altimeters come in various shapes, sizes and packages, and are used for a multitude of activities, such as hiking, skydiving and flying planes.
People often use altimeters for work, leisure activities and sometimes more serious endeavors such as search and rescue missions. Skydivers use them to know the exact elevation to deploy their parachutes. Hikers can use them to gauge their location on a mountain peak or backcountry trail. Pilots use altimeters to note their elevation, without which ascending, landing, and avoiding the flight paths of other planes would be far more dangerous. When camping, it may help to know one's elevation to assess how long food will take to cook over a fire. Researchers also often use altimeters when sending objects in flight.
Digital altimeters come with a variety of elevation ranges. Some give accurate measures from sea level to 2,000 feet, while others can calculate your height even at the top of Mt. Everest. For the right price, one can purchase a digital altimeter capable of a far greater range than the average instrument. Naturally, the necessary range one needs depends on the particular activity for which the altimeter will be used.
With analog altimeters, one can get an idea of whether adverse weather might by on the way if the instrument's readings are less than accurate. This is due to the fact that altimeters are also barometers, and any atmospheric pressure change caused by weather will influence the reading. So it is with many digital altimeters as well, but the savvy user no longer has to craftily interpret one altimeter reading for multiple purposes; one can simply buy a device that functions as both a digital altimeter and a weather barometer. In fact, digital technology has allowed the outdoorsman to use all-in-one altimeters that can handle far more than two functions: they can tell time, serve as a compass guide, gauge weather conditions, and even be used as a thermometer.
Each time a digital altimeter is used, it's wise to adjust it to account for weather conditions. Pressure changes in the air due to inclement weather can skew a reading by multiple feet, which over the course of a few hours can add up to a woefully inaccurate reading. In order to compensate for this, one simply adjusts the digital altimeter to the current atmospheric pressure of his or her location. Current barometric pressure conditions can be obtained from a variety of weather sources via radio, TV and Internet.
Altimeters aren’t the only device that can automatically track elevation; Global Positioning System (GPS) devices can also calculate elevation using satellites to pinpoint an object’s coordinates. GPS devices are not, however, true altimeters, because they don’t measure barometric pressure. In the outdoor world, devices that function as both a GPS and an altimeter have grown in popularity. The use of two simultaneous systems to better pinpoint elevation has resulted in digital altimeter/GPS devices capable of delivering more precise altitude readings.