density altitude?

Answer 1

Air molecules are affected by gravity, so that the density of air is greater near sea level than it is at high elevation. This is a predictable and measurable affect. The barometric altimeter in your airplane instruments is calibrated for the change in pressure with altitude. However weather patterns cause small changes in total barometric pressure, so the altimeter requires a slight correction to be applied to be accurate. This correction is available from the airport weather station as conditions change.

Because so many planes use barometric altimeters, those pilots that have radar or radio altimeters have to be aware that other planes may be flying at the barometric altitude.

Answer 2

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