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Minimum Safe Altitude
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Minimum Safe Altitude is a generic expression, used in various cases to denote an altitude below which it is unsafe to fly owing to presence of terrain or obstacles. An ICAO definition of a term "minimum safe altitude" as such does not exist.
Minimum altitudes are calculated in relation to the highest terrain or obstacle within a specified area, allowing a buffer for error, and adding a specified margin.
The expression "minimum safe altitude" is also used in relation to the MSAW function of ATC systems.
Note. The acronym MSA is also often used in place of 'minimum safe altitude' however that term may be defined in a given circumstance. Since this is contrary to the ICAO definition of the acronym for Minimum Sector Altitude, where the abbreviation is encountered, care should be taken to establish which term it refers to.