Terrain Proximity - Garmin G900X Pilot's Manual

6.2 TERRAIN PROXIMITY

WARNING:
intended only to enhance situational awareness.
Terrain data is not displayed when the aircraft latitude is greater than 75 ° North or 60 ° South.
NOTE:
G900X Terrain Proximity is a non-TSO-C151b-certified terrain awareness system. It increases situational
awareness and aids in reducing controlled flight into terrain (CFIT). Do not confuse Terrain Proximity with
Terrain Awareness and Warning System (TAWS). TAWS is more sophisticated and robust, and it is TSO-C151b
certified. Terrain Proximity does not provide warning annunciations or voice alerts. It only provides color
indications on map displays when terrain and obstacles are within a certain altitude threshold from the aircraft.
Although the terrain and obstacle color map displays are the same, TAWS uses more sophisticated algorithms to
assess aircraft distance from terrain and obstacles.
Terrain Proximity requires the following components to operate properly:
• Valid 3-D GPS position
• Valid terrain/obstacle database
Terrain Proximity 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 G900X GPS receiver provides the horizontal position and altitude. 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 Proximity
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.
190-00726-00 Rev. A
Do not use Terrain Proximity information for primary terrain avoidance. Terrain Proximity is
Garmin G900X Pilot's Guide
HAZARD AVOIDANCE
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