Garmin aera 795/796 Pilot’s Guide 190-01194-00 Rev. A96Hazard AvoidanceOverviewGPS NavigationFlight PlanningHazard AvoidanceAdditional FeaturesAppendicesIndexNote 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 theaircraft. Aircraft GPS altitude is derived from satellite position. GPS altitude is thenconverted to a mean sea level (MSL)-based altitude (GPS-MSL altitude) and is used todetermine terrain and obstacle proximity. GPS-MSL altitude accuracy is affected bysatellite geometry, but is not subject to variations in pressure and temperature thatnormally affect pressure altitude sensors. GPS-MSL altitude does not require localaltimeter settings to determine MSL altitude. It is a widely-used MSL altitude source.Terrain and obstacle databases are referenced to MSL. Using the GPS positionand altitude, the Terrain feature portrays a 2-D picture of the surrounding terrain andobstacles 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 thesurrounding terrain and obstacles. In this way, the pilot can view predicted dangerousterrain 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 inthe Terrain Setup.TERRAIN INFORMATIONTwo 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 orabove the aircraft. The yellow terrain areas are between the user-defined CautionElevation and 100 feet below the aircraft. By default, the Caution Elevation is 1,000feet; therefore, the areas in yellow are between 1,000 feet and 100 feet below theaircraft. The black areas are further than the Caution Elevation. A projected point ofimpact is marked with an “X” symbol.OBSTACLE INFORMATIONObstacles 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 nmor below.
