In the altimeter what is it measuring in AGL or MSL or ASL?

Answer 1

Altitude above MSL (Mean Sea Level). Altimiters work on differences in air pressure and have to be recalibrated for the local barometer settings as you move from area to area. Only a radar alitimeter can give you AGL info.

Answer 2

MSL usually.

A barometric altimeter is usually set to QNH, QNE and in some countries like Russia, QFE.

Q is Morse code for station (weather station at an airport).

NH = Normal Height or height above mean sea level when using the local station pressure and standard temperature.

NE = Normal Enroute or approximate height above mean sea level when in the Flight Levels. An aircraft transitions from QNH setting to QNE passing 18,000 feet in the US airspace and possibly much lower altitudes in other regions. This puts all aircraft in flight levels at the same altimeter setting: 29.92 in. Hg (mercury) or 1013.2 millibars or hectopascals in the metric system.

FE = Field Elevation
QFE can be used for an approach to a specific runway so that the altimeter reads meters above touchdown zone elevation. The altimeter would then read zero at touchdown.

Aircraft that have GPWS (Ground Proximity Warning System) installed have a Radio Altimeter. It becomes usable below 2500 feet above the ground. So it shows height above the terrain or Absolute Altitude.

Answer 3

The pressure altimeter measure altitudes with respect to what it believes to be zero. If you set the zero altitude as MSL, it will read in terms of height above MSL and likewise for AGL, ASL.

Answer 4

Altimeters measure MSL unless you have a radar altimeter which reads the terrain below an aircraft. In that case you are reading distance AGL

Answer 5

MSL ( mean sea level) For example. If the field elevation is zero feet, then the altimeter reads zero. But if you are on the ground at an airport with an elevation of 1000 feet above sea level, the altimeter will read 1000 feet. Unless it isn't adjusted to for the current atmospheric pressure (barometer), then it could read higher or lower then 1000 ft.

Answer 6

The altimeter measures air pressure; adiabatic lapse, (one of those five dollar words I don't get to use very often,) is the decrease in density of air pressure as altitude increases.

The altimeter displays one's elevation above MSL, meaning mean, (average, thanks to tides,) sea level. So if you're in my neighborhood where the surveyed height of the ground is about 650' above MSL, your altimeter is correctly set and showing 2,000', you're 2,000 MSL and 1350' AGL.

ASL is the abbreviation for absolute sea level, and only used for flights above 18,000'. That benchmark seperates for the most part, the pistons poppers from the jets. Above 18,000' everyone dials their altimeters to ground, air pressure reading of 29.92 in. HG and all the traffic simply moves up and down at the same time as the atmospheric pressures they move through change.

Theoretically, your flight at 35,000' could be off by as much as a thousand feet, but all the other aircraft in the same flight level, or adjacent flight levels, are reading the same altitude that you are, minimizing the risks collisions.

It sounds better to say "we're going to reach our cruising altitude of FL360" than it does to say "we're going to reach our cruising altitude of 36,000', give or take."

Answer 7

depends on what QNH you set dude.