Minimum Safe Altitude Warning (MSAW) is an automated warning system for air traffic controller

Air traffic controller

Air traffic controllers are the people who expedite and maintain a safe and orderly flow of air traffic in the global air traffic control system. The position of the air traffic controller is one that requires highly specialized skills...

s (ATCO). It is a ground-based safety net intended to warn the controller about increased risk of controlled flight into terrain

Controlled flight into terrain

Controlled flight into terrain describes an accident in which an airworthy aircraft, under pilot control, is unintentionally flown into the ground, a mountain, water, or an obstacle. The term was coined by engineers at Boeing in the late 1970s...

 accidents by generating, in a timely manner, an alert of aircraft proximity to terrain or obstacles.

Description

ICAO Doc 4444 requires that radar systems should provide for the display of safety-related alerts including the presentation of minimum safe altitude warning. It is worth mentioning that ICAO Doc 4444 does not provide a definition of the term MSAW. Instead the term MSAW is ambiguously used in ATC

Air traffic control

Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...

community to identify such warnings as well as for data processing systems providing the alert function.