Look–Ahead Terrain Alerting
The GPWS terrain data base contains detailed terrain data near major airports, and data in
lesser detail for areas between airports. Terrain within 2,000 feet of
airplane barometric altitude shows on the navigation display. The terrain data is
not designed to be an independent navigation aid.
Note: The GPWS terrain data base, look-ahead terrain alerting, and terrain
display do not account for man made obstructions.
The terrain display is generated from a data base contained in the GPWS computer and
correlated to GPS position. Terrain and weather radar cannot show together on a display.
If one pilot selects terrain and the other pilot selects weather radar, each display updates
on alternating sweeps. All other displays (TCAS, LNAV routing, etc.) can show with terrain
data. Look-ahead terrain alerts are based on the airplane’s position, barometric altitude,
vertical flight path, and ground speed.
