10-6
GTN 625/635/650 Pilot’s Guide
190-01004-03 Rev. P
Terrain
10.4
Terrain Proximity
Garmin Terrain Proximity is a non-TSO-C151c-certified terrain awareness
system provided as a standard feature of GTN 6XX to increase situational
awareness and help reduce controlled flight into terrain (CFIT). Terrain may be
displayed on the Map and Terrain pages.
Terrain Proximity uses information provided from the GPS receiver to
provide a horizontal position and altitude. GPS altitude is derived from satellite
measurements. GPS altitude is converted to a Mean Sea Level (MSL)-based
altitude (GSL altitude) and is used to determine Terrain alerts. GSL altitude
accuracy is affected by factors such as satellite geometry, but it is not subject
to variations in pressure and temperature that normally affect pressure altitude
devices. GSL altitude does not require local altimeter settings to determine MSL
altitude. Therefore, GPS altitude provides a highly accurate and reliable MSL
altitude source to calculate terrain and obstacle alerts.
Terrain Proximity utilizes terrain and obstacle databases that are referenced
to mean sea level (MSL). Using the GPS position and GSL altitude, Terrain
Proximity displays a 2-D picture of the surrounding terrain and obstacles relative
to the position and altitude of the aircraft. In this manner, Terrain Proximity can
provide advanced alerts of predicted dangerous terrain conditions.
Terrain Proximity requires the following to operate properly:
• The system must have a valid 3-D GPS position solution.
• The system must have a valid terrain/obstacle database.
360
Arc
View
Flight Plan
Legend
Layers
Figure 10-1 Terrain Proximity Page Functional Diagram
Summary of Contents for GTN 625
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