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Africa, Australia) use the airport's AMSL (above mean sea level) elevation as a reference. During approaches to landing, there are several other references that are used, including AFE (above field elevation) which is height referencing the highest point on the airfield, TDZE (touchdown zone elevation) or TH (threshold height) which both refer to the elevation of the landing end of the runway measured AMSL and AGL respectively.
211:, can therefore be set in such a way as to indicate the height of the aircraft above ground. This is done by communicating with the control tower of the airport (to get the current surface pressure) and setting the altimeter so as to read zero on the ground of that airport. Confusion between AGL and AMSL, or improper calibration of the altimeter, may result in
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In weather and climate studies, measurements or simulations often need to refer to a specific height or altitude, which is naturally AGL. However, the values of geophysical variables measured in various places on the natural (ground) surface may not be easily compared in hilly or mountainous terrain,
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that provides a zero reading on the ground of the airport is a reference available to pilots, in commercial aviation it is a country-specific procedure that is not often used (it is used, e.g., in Russia, and a few other countries). Most countries (Far East, North and South
America, all of Europe,
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system, which is the ratio of the pressure at a location (latitude, longitude, altitude) divided by the pressure at the nadir of that location on ground surface (same latitude, same longitude, altitude AGL = 0).
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because part of the observed variability is due to changes in the altitude of the surface. For this reason, variables such as pressure or temperature are sometimes 'reduced' to mean sea level.
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In general, "altitude" refers to distance above mean sea level (MSL or AMSL), "height" refers to distance above a particular point (e.g. the airport,
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is explicitly represented, the altitudes of these locations are set above the simulated ground level. This is often implemented using the so-called
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Procedures for Air
Navigation Services – Aircraft Operations (PANS-OPS), Volume II: Construction of Visual and Instrument Flight Procedures
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298:. In this case, height AGL is the only important measurement for aviation authorities, which require that some tall towers have proper
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of a station. Rather, it is HAAT (the height above the average terrain (in the surrounding area)) which is used to determine how far a
230:, or ground at present location), and "elevation" describes a feature of the terrain itself in terms of distance above MSL.
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78:). In other words, these expressions (AGL, AMSL, HAE, AAT) indicate where the "zero level" or "reference altitude" – the
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of the plane with respect to the landing area (usually an airport). The altimeter, which is usually a
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From aviation safety perspective though, the more important aspect is the height of the
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are specified or computed at a number of discrete locations and heights. When the
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and prepare for landing. Therefore, the pilot needs reliable information on the
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In broadcasting, altitude AGL has relatively little direct bearing on the
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List of aviation, avionics, aerospace and aeronautical abbreviations
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215:, a crash of a fully functioning aircraft under pilot control.
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Height measured with respect to the underlying ground surface
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The
Private Pilot's Licence Course: Navigation, Meteorology
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352:. UK Civil Aviation Authority. 28 May 2015.
113:aviation, atmospheric science, broadcasting
207:calibrated in units of distance instead of
70:(HAE, as reported by a GPS receiver), or
191:conditions) must rely on the aircraft's
58:measured with respect to the underlying
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246:, the state and properties of the
242:In general circulation models and
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183:A pilot flying an aircraft under
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62:. This is as opposed to height
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218:While the use of a barometric
213:controlled flight into terrain
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414:(3rd ed.). met22–met23.
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195:to decide when to deploy the
164:height above average terrain
287:) transmission will travel.
170:average surrounding surface
130:nautic, technics, geography
127:height above mean sea level
72:height above average terrain
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410:Pratt, Jeremy M. (2003) .
325:Index of aviation articles
110:height above ground level
44:height above ground level
185:instrument flight rules
144:height above ellipsoid
385:. 2006. Archived from
300:aircraft warning paint
279:(or any other sort of
187:(typically under poor
68:height above ellipsoid
476:Broadcast engineering
461:Altitudes in aviation
350:Radiotelephony Manual
330:Minimum safe altitude
244:global climate models
136:barometric altimeter
76:broadcast engineering
466:Aviation meteorology
294:used to support the
234:Atmospheric sciences
209:atmospheric pressure
147:navigation, science
64:above mean sea level
36:atmospheric sciences
150:math surface model
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444:2007-09-28 at the
133:sea level average
102:Measuring devices
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18:Above ground level
277:broadcast station
220:altimeter setting
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74:(AAT or HAAT, in
66:(AMSL or HAMSL),
16:(Redirected from
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381:(5th ed.).
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359:9780-11792-893-0
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260:sigma coordinate
228:runway threshold
119:radar altimeter
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394:. Retrieved
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267:Broadcasting
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124:AMSL, HAMSL
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40:broadcasting
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292:radio tower
99:Zero level
96:Main usage
93:Stands for
455:Categories
396:2015-08-15
336:References
308:collisions
283:or higher
256:continents
252:topography
248:atmosphere
189:visibility
161:AAT, HAAT
107:AGL, HAGL
362:. CAP413.
306:to avoid
205:barometer
193:altimeter
442:Archived
314:See also
179:Aviation
32:aviation
254:of the
54:) is a
471:Clouds
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304:lights
201:height
56:height
390:(PDF)
379:(PDF)
152:WGS84
416:ISBN
383:ICAO
354:ISBN
302:and
141:HAE
52:HAGL
42:, a
38:and
281:VHF
50:or
48:AGL
30:In
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34:,
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46:(
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