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Are altimeters accurate?
With proper calibration, the barometric altimeter of an outdoor watch or handheld will report elevation readings ranging from -2,000 to 30,000 feet with an accuracy of +/-50 feet. Elevation values greater than 30,000 feet can be generated, but may not be accurate due to environmental factors.
How accurate is GPS elevation data?
Elevation calibrated by GPS is accurate to +/-400 feet with a strong GPS signal. Elevation is determined by the device acquiring a GPS signal, while maps will provide elevation information based on survey data.
Can GPS detect altitude?
GPS watches with barometer measure ambient air pressure to calculate altitude and altitude changes. In general, air pressure gets lower when ascending and gets higher when descending. The watch calculates your current altitude based on: Your surrounding air pressure AND.
How does a barometric altimeter measure altitude?
Barometric altimeters measure altitude above a standard reference (usually sea level) by using a known/standard pressure lapse rate (~1 in.Hg per 1,000 feet) and measuring the difference in pressure at the instrument.
How is the altimeter in a GPS watch accurate?
But altitude is not the only factor that causes variations in pressure; weather changes do too (high temperature = pressure drop, and vice versa). So, to get an accurate reading, a traditional barometric altimeter watch would need to be calibrated almost on a daily basis to match the known reference height.
What is the precision of a digital altimeter?
Digital altimeters are extremely precise (often offering one-foot precision in their display, and 0.01 inches of mercury for the pressure setting). I believe the precision requirements for altimeter markings are specified in the relevant TSOs, but I don’t have those documents handy.
What do you need to know about a mechanical altimeter?
A mechanical altimeter has a knob that needs to be manually adjusted to make it point to 0 on the ground before jump, and if the landing spot is not at the same altitude as the takeoff spot, the user needs to adjust it appropriately.