In aviation

Aviation

Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

, minimum reception altitude (MRA) is the lowest altitude on an airway

Airway (aviation)

In aviation, an airway is a designated route in the air. Airways are laid out between navigational aids such as VORs, NDBs and Intersections ....

 segment where an aircraft

Aircraft

An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 can be assured of receiving signals from navigation aid

Radio navigation

Radio navigation or radionavigation is the application of radio frequencies to determine a position on the Earth. Like radiolocation, it is a type of radiodetermination.The basic principles are measurements from/to electric beacons, especially...

s like VOR

VHF omnidirectional range

VOR, short for VHF omnidirectional radio range, is a type of radio navigation system for aircraft. A VOR ground station broadcasts a VHF radio composite signal including the station's identifier, voice , and navigation signal. The identifier is typically a two- or three-letter string in Morse code...

 or NDB

Non-directional beacon

A non-directional beacon is a radio transmitter at a known location, used as an aviation or marine navigational aid. As the name implies, the signal transmitted does not include inherent directional information, in contrast to other navigational aids such as low frequency radio range, VHF...

. Typically, the greater the distance between navigation aids, the higher the MRA. MRA is becoming less important with the availability of GPS satellite navigation, which allows aircraft to get navigational guidance all the way down to the ground.

See also

• Above ground level
  Above ground level
  In aviation and atmospheric sciences, an altitude is said to be above ground level when it is measured with respect to the underlying ground surface. This is as opposed to above mean sea level , or in broadcast engineering, height above average terrain...
  
  
• Minimum enroute altitude
  Minimum enroute altitude
  Minimum en route altitude , alternately spelled as Minimum enroute altitude, is the lowest published altitude between radio navigation fixes that assures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes.The definition given here is that of the...
  
   (MEA)
• Minimum obstacle clearance altitude
  Minimum obstacle clearance altitude
  Minimum Obstacle Clearance Altitude, or MOCA, is the lowest published altitude in effect between fixes on VOR airways, off-airway routes, or route segments that meets obstacle clearance requirements for the entire route segment. Within the United States, this altitude also assures acceptable...
  
   (MOCA)
• Minimum safe altitude
  Minimum safe altitude
  Minimum safe altitude is a concept used in planning and executing aircraft flights. It is an altitude which allows adequate vertical clearance from nearby terrain and manmade obstacles, and allows proper navigational functions.-IFR flights:...