Avidyne IFD550 - Page 210

IFD500 Series Pilot Guide
4-54 Map Subsystem
 GPS position accuracy is excessively low
 Terrain database is invalid or not available
 Obstacle database is invalid or not available
 Nav database is invalid or not available
 Aircraft is on the ground
 The system is configured for an external TAWS system
 The TAWS option is not enabled