Altimeter / Barometer

Firefighters use an altimeter/barometer to measure elevation.  The altimeter/barometer can provide a sufficiently accurate identification of a location.   But, firefighters can use a compass and a topographic map in combination with an altimeter/barometer to confirm or get a more precise identification of their location. 

Changes in weather patterns may affect the altimeter/barometer.  The altimeter/barometer uses pressure differences to record elevation, so a change in atmospheric pressure after the reference elevation is set, may lead to spurious readings thereafter.  It is good practice to continuously check altimeter/barometer readings throughout the period of use against additional reference elevations.

Global positioning systems (GPS) also note elevations without regard to atmospheric pressure.  However, GPS elevational error is around +/- 50-to-65 feet (15 to 20 meters).

Altimeter/barometers can be purchased with either English or metric displays.