Htaws Operation - Garmin GTN 625 Pilot's Manual

10.4.1.3
Foreword
NOTE: The data contained in the terrain and obstacle databases comes
Getting
from government agencies. Garmin accurately processes and cross-
Started
validates the data, but cannot guarantee the accuracy and completeness
of the data.
Xpdr Ctrl
HTAWS displays terrain and obstructions relative to the flight path of the
Com/Nav
aircraft. Individual obstructions may be shown if available in the database.
However, all obstructions may not be available in the database and data may be
FPL
inaccurate. Never use this information for navigation.
Direct-To
NOTE: Terrain databases do not consistently represent foliage. Some trees
may extend above HTAWS protection limits in some operating modes.
Proc
Terrain information is based on terrain elevation data contained in a database
Wpt Info
that may contain inaccuracies. Terrain information should be used as an aid
to situational awareness. Never use it for navigation or to maneuver to avoid
Map
terrain.
HTAWS uses terrain and obstacle information supplied by government
Traffic
sources. The data undergoes verification by Garmin to confirm accuracy of the
content. However, the displayed information should never be understood as
Terrain
being all-inclusive.
Weather
10.4.2
Nearest
10.4.2.1
Services/
HTAWS uses information provided from the GPS receiver to provide
Music
a horizontal position and altitude. GPS altitude is derived from satellite
Utilities
measurements. GPS altitude is converted to a mean sea level (MSL)-based
altitude (GSL altitude) and is used to determine HTAWS alerts. GSL altitude
System
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
Messages
devices. GSL altitude does not require local altimeter settings to determine MSL
altitude. Therefore, GPS altitude provides a highly accurate and reliable MSL
Symbols
altitude source to calculate terrain and obstacle alerts.
Appendix
HTAWS utilizes terrain and obstacle databases that are referenced to mean
sea level (MSL). Using the GPS position and GSL altitude, HTAWS displays a
Index
2-D picture of the surrounding terrain and obstacles relative to the position and
10-20
Limitations

HTAWS Operation

HTAWS Alerting
Garmin GTN 625/635/650 Pilot's Guide 190-01004-03 Rev. F