Garmin G500 Pilots Guide - Page 131

Foreword Sec 1 System Sec 2 PFD Sec 3 MFD 4.2 Terrain Proximity Garmin TERRAIN is a non-TSO-C151b-certified terrain awareness system provided as a standard feature of GDU 620 to increase situational awareness and help reduce controlled flight into terrain (CFIT). Terrain may be displayed on the Map page group Navigation 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 (GPS-MSL altitude) and is used to determine TERRAIN alerts. GPS-MSL 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. GPS-MSL 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 GPS-MSL 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 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/airport terrain database. Sec 4 Hazard Avoidance Features Sec 5 Additional Sec 6 Annun. & Alerts Sec 7 Symbols Sec 8 Glossary Appendix A Appendix B Index 190-01102-02 Rev. B Garmin G500 Pilot's Guide 4-3