User guide

Rev 2.3 Feb.12 205
D : Global Positioning System (GPS)
• Configuring the
AirLink Device for
GPS
• RAP Configuration
• NMEA
Configuration
• TAIP Emulation
Configuration
The AirLink device is equipped with a Global Positioning System
receiver (GPS) to ascertain its position and track the movements of a
vehicle or other devices which move. The AirLink device relays the
information of its location as well as other data for use with tracking
applications.
Tracking Applications used with Sierra Wireless PinPoint line
modems:
• Air-Trak
• Track Your Truck
• Tra ck S t a r
• DeLorme Street Atlas USA
• Microsoft Streets and Trips
• CompassCom
• Zoll Data
GPS Overview
The Global Positioning System (GPS) is a satellite navigation system
used for determining a location and providing a highly accurate time
reference almost anywhere on Earth. The US military refers to GPS
as Navigation Signal Timing and Ranging Global Positioning System
(NAVSTAR GPS).
GPS consists of a “constellation” of at least 24 satellites in 6 orbital
planes. Each satellite circles the Earth twice every day at an altitude
of 20,200 kilometers (12,600 miles). Each satellite is equipped with
an atomic clock and constantly broadcasts the time, according to its
own clock, along with administrative information including the orbital
elements of its motion, as determined by ground-based
observatories.
A GPS receiver, such as the AirLink device, requires signals from four
or more satellites in order to determine its own latitude, longitude,
and elevation. Using time synced to the satellite system, the receiver
computes the distance to each satellite from the difference between
local time and the time the satellite signals were sent (this distance is
called psuedoorange). The locations of the satellites are decoded
from their radio signals and a database internal to the receiver. This
process yields the location of the receiver. Getting positioning