Maximum elevation figure (MEF) is a type of
visual flight rule (VFR) information that indicates the
elevation
The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § ...
of the highest
geographical feature within a
GEOREF quadrangle area. It is of interest to pilots, who want to be aware of the highest mountain peaks and tall towers nearby, so that they can fly above them to avoid
controlled flight into terrain
In aviation, a controlled flight into terrain (CFIT; usually ) is an accident in which an airworthy aircraft, under pilot control, is unintentionally flown into the ground, a mountain, a body of water or an obstacle. In a typical CFIT scenari ...
. ("Features" includes terrain, trees, towers, and other obstacles.)
Much like the
minimum safe altitude (MSA) used for flight under
instrument flight rules
In aviation, instrument flight rules (IFR) is one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other is visual flight rules (VFR).
The U.S. Federal Aviation Administration's (FAA) ''Instrument F ...
, the MEF includes a margin for aircraft clearance ''above'' the terrain and
altimeter
An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. The m ...
error.
[Aeronautical Information Circular 26/11 VFR Navigation Charts—Clarification of the Maximum Elevation Figure](_blank)
/ref>
In a VFR flight, the MEF is commonly referred to as a "quadrantal altitude" (not to be confused with an IFR minimum sector altitude).
United States
In the US, the Federal Aviation Administration
The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...
issues sectional charts. Each rectangular area covering one degree of latitude and one degree of longitude is divided into four smaller areas called ''quadrangles'' (in accordance with the World Geographic Reference System, or GEOREF), each spanning half a degree of latitude and half a degree of longitude. Each quadrangle has its MEF printed in it in thousands and hundreds of feet above mean sea level. For example, 105, means that the highest elevation is 10,500 feet within that quadrangle.
MEFs are determined by taking the highest of the following:
1) The point of highest ''terrain'' within a quadrangle, adding 200 ft for obstacles which are not required to be portrayed, and then adding 100 feet for vertical error and then rounding up to the next hundred feet; or
2) The height of the highest ''manmade obstacle'' in the quadrangle, adding 100 feet for vertical error
and then rounding up to the next hundred feet.[
]
Canadian VNCs
The MEF on Canadian
Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...
VFR navigation charts is calculated by taking the higher value of:
* the top elevation of the highest obstacle plus the vertical accuracy (a variable number of feet) of the terrain source data; or
* the elevation of the highest terrain plus 328 feet plus the vertical accuracy variable of the terrain source data.
Australia
In Australia, Visual Navigation Charts (VNCs) and Visual Terminal Charts (VTCs) usually indicate MEF information by use of bold elevation figures for each grid. Pilots are also required to ensure their planned route does not contravene the minimum flying altitude regulations contained i
CAR 167
This restriction is normally 1000FT above populated or built-up areas and 500FT elsewhere.
Procedures are different when flights are conducted under IFR, where LSALT is commonly used. LSALT may be determined in a number of ways as explained in the Australian Aeronautical Information Publication o
AIP
See also
* Minimum safe altitude (for IFR flight), including area minimum altitudes (AMA)
References
Altitudes in aviation
Cartography
Highest points
{{cartography-stub