How do flight computers in planes know how high above the ground they are.

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How do flight computers in planes know how high above the ground they are.

In: Technology

So there are a few ways.

– Barometric altimeters measure the atmospheric pressure outside the plane and use that to (fairly accurately) estimate the height above sea level. This works because atmospheric pressure drops at a predictable rate as you increase your altitude, but because air pressure in a region can fluctuate you may need to adjust for local conditions. This gives you your elevation above sea level, so you have to calculate your height above ground based on your exact location.

– Radar altimeters bounce radio waves off the ground beneath the plane and measure the time it takes for the waves to return. Since radio waves travel at a constant, known speed, you can measure your height above the ground this way.

– GPS altimeters use satellites orbiting Earth to pinpoint your exact location, in three dimensions. They work on a similar principle as radar, but instead of measuring your distance to the ground, they measure your distance from three (or more) satellites. If you know the location of the satellites and you know your distance from them, then you know your location. This, obviously, gives you your altitude.

Different planes may use one, two, or a combination of all three of these to give an accurate and reliable measurement of altitude.