Garmin Pilot Guida Utente

190-01501-00 Rev. N

175

 WARNING: Do not use Terrain information for primary terrain avoidance.  

Terrain information is intended only to enhance situational awareness.

The Terrain function displays altitudes of terrain and obstructions relative to 

the aircraft position and altitude with reference to a database that may contain 
inaccuracies.  Terrain and obstructions are shown only if they are in the database.  
Terrain and obstacle information should be used as an aid to situational awareness.  
They should never be used to navigate or maneuver around terrain.

Note that all obstructions may not be available in the terrain and obstacle database.  

No terrain and obstacle information is shown without a valid 3-D GPS position.

The device or external GPS receiver provides the horizontal position and altitude of 

the aircraft.  Aircraft GPS altitude is derived from satellite position.  GPS altitude is then 
converted to a mean sea level (MSL)-based altitude (GPS-MSL altitude) and is used to 
determine terrain and obstacle proximity.  GPS-MSL altitude accuracy is affected by 
satellite geometry, but is not subject to variations in pressure and temperature that 
normally affect pressure altitude sensors.  GPS-MSL altitude does not require local 
altimeter settings to determine MSL altitude.  It is a widely-used MSL altitude source.

Terrain and obstacle databases are referenced to MSL.  Using the GPS position 

and altitude, the Terrain feature portrays a 2-D picture of the surrounding terrain and 
obstacles relative to the position and altitude of the aircraft.  GPS position and GPS-
MSL altitude are used to calculate and predict the aircraft’s flight path in relation to the 
surrounding terrain and obstacles.  In this way, the pilot can view predicted dangerous 
terrain and obstacle conditions.

Alert windows appear to inform the pilot of proximity to the terrain and obstacles.