Terrain Information; Obstacle Information - Garmin aera 796 Pilot's Manual

Hazard Avoidance
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 aera 795/796 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,
as well as an unsafe descent rate. These alerts depend on user-defined parameters in
the Terrain Setup.

TERRAIN INFORMATION

Two views are displayed by the Terrain function: the Map View, and the Profile View.
The areas of the terrain shaded red are predicted to be within 100 feet below or
above the aircraft. The yellow terrain areas are between the user-defined Caution
Elevation and 100 feet below the aircraft. By default, the Caution Elevation is 1,000
feet; therefore, the areas in yellow are between 1,000 feet and 100 feet below the
aircraft. The black areas are further than the Caution Elevation. A projected point of
impact is marked with an "X" symbol.

OBSTACLE INFORMATION

Obstacles are shown on the Terrain Map View, at or below the map range of 12 nm.
Obstacles are also shown on the Navigation Map when the map range is set to 5 nm
or below.
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Garmin aera 795/796 Pilot's Guide 190-01194-00 Rev. A