Garmin GPS Receiver 400/500 User Manual download pdf (Page 37)

Section 1

Introduction

Figure 1-1: The Garmin TERRAIN system offers many

of the features of Garmin TAWS but is non-TSO-

C151b-certiﬁed.

PART THREE

TERRAIN INTERFACE

Section 1: Introduction

Overview

Garmin TERRAIN is a non-TSO-C151b-certiﬁed terrain awareness system incorporated into 400/500

Series units to increase situational awareness and aid in reducing controlled ﬂight into terrain (CFIT).

TERRAIN functionality is a standard feature found in 400 Series units with main software version 5.01

or above, and in 500 Series units with main software version 6.01 or above, along with appropriate

hardware upgrades.

Operating Criteria

The Garmin TERRAIN system requires the following to operate properly:

• The system must have a valid 3D GPS position solution

• The system must have a valid terrain/obstacle database

GPS Position and GPS-MSL Altitude

Garmin TERRAIN uses information provided by the 400/500 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 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.

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Garmin GPS Receiver 400/500 User Manual Page 37