The D2 packs a chronograph,
pressure altimeter, thermometer, compass and an aviation GPS.
Despite the
pressure altimeter being a marvel of mechanical engineering, it is error-prone.
Abstract: Variation in atmospheric pressure is a potential source of information that might be used by flying animals as the basis of a
pressure altimeter and/ or meteorological forecasting.
I heard "Altitude, altitude!" My eyes darted to the
pressure altimeter and caught the thin needle racing through 3,500 feet.
We even had time to reset our
pressure altimeter to the exact local pressure by first descending to 400 ft.
As I read that, I reflected on my airline days where we used a
pressure altimeter set to read our height above the airport.
Along the lower edge of the screen, the XRX displays "local" heading and altitude, which are data points taken from the device's onboard compass and
pressure altimeter. If wired into the ship's audio, the XRX issues traffic alerts aurally, beginning with a voice advisory and beeps at .6 to 2 miles, escalating to a warning and four beeps at .3 to .7 miles.
Variation in atmospheric pressure is a potential source of information that might be used by animals as the basis of a
pressure altimeter and/or meteorological forecasting.
With a chronograph,
pressure altimeter, compass and thermometer inside, you get a lot of pilot stuff in one package.
The result is that on a hot day on the glidepath, your
pressure altimeter will indicate lower over a fix than on a cold day, and you might bust that crossing altitude.
Let's put you back on the ILS to 30R and see the results when you reach DH (at -25 degrees C) as indicated on the panel-mount
pressure altimeter. The DH is 1073, which is 250 HAT.
Pressure altimeters are calibrated to indicate true altitude (actual height above sea-level) under standard conditions only, and any deviation from standard conditions produces an error in the indicated altitude.