Terrain Proximity; Displaying Terrain Proximity Data - Garmin G900X Pilot's Manual

HAZARD AVOIDANCE

6.5 TERRAIN PROXIMITY

Do not use Terrain Proximity information for primary terrain avoidance. Terrain Proximity is
WARNING:
intended only to enhance situational awareness.
Terrain data is not displayed when the aircraft is outside of the installed terrain database coverage
NOTE:
area.
G900X Terrain Proximity is a terrain awareness system that does not comply with TSO-C151b certification
standards. It increases situational awareness and aids in reducing controlled flight into terrain (CFIT). Do not
confuse Terrain Proximity with the optional Terrain Awareness and Warning System - Class B (TAWS-B). TAWS-B
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-B 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 the height above geodetic sea level (GSL), which is the height above
mean sea level calculated geometrically. GSL altitude is used to determine terrain and obstacle proximity. GSL
altitude accuracy is affected by satellite geometry, but is not subject to variations in pressure and temperature that
normally affect pressure altitude sensors. GSL 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 GSL 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.

DISPLAYING TERRAIN PROXIMITY DATA

The symbols and colors in Figure 6-119 and Table 6-16 are used to represent obstacles and aircraft altitude
when the Terrain Proximity Page is selected for display. Terrain Proximity uses black, yellow, and red to
represent terrain information relative to aircraft altitude. The color of each obstacle is associated with the
altitude of the aircraft.
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Garmin G900X Pilot's Guide
190-00726-00 Rev. J