Pettec 15256 Einleitung Seite 25

Positioning methods
GPS tracking only functions outdoors when our tracker can make contact with 3 satelli-
tes. The triangulation of 3 satellites determines the location to within 5m exactly.
Distance measurement
If the tracker can't find a connection to any satellites, the tracker will automatically
switch to the so-called LBS location method. In this location method, the tracker can
only determine the signal strength to the nearest three cellular towers. Since the signal
strength is strongly influenced by the environment, the positioning as well as distance to
the towers, this positioning is less accurate than satellites. This limits the search area to
a radius of approximately 1 km if the tracker doesn't have GPS reception.
Signal strength measu-
rement
Accurate GPS tracking
Possible limitation of the GPS signal:
• In buildings or tunnels
• Under bridges and overpasses
• Terrain (mountains, trees, etc.)
LBS area tracking
25