FENDT varioguide, Operator'S Manual

Page: 21 / 158

3.1 Definitions
3.1.1 GNSS and correction signal
GNSS (Global Navigation Satellite System) is a global navigation satellite system designed for position
determination and navigation using satellite signals and signals received from pseudolites (terrestrial
transmitters which emit signals like those of a satellite).
Data for position determination is currently supplied by North America's NAVSTAR GPS and Russia's
GLONASS system. Galileo, the European satellite navigation system, is currently under development.
VarioGuide processes both GPS and GLONASS signals and is designed to operate with future systems.
GNSS satellites communicate their exact position and time via radio. For position determination a receiver
has to be supplied with signals from at least four satellites simultaneously. The four signal propagation
times (from the satellites to the receiving aerial) are then calculated in the receiving device. This is used to
determine the current position.
Stationary receiving stations improve positional accuracy by transmitting correction signals (DGPS) to
users:
• with geostationary satellites such as Europe's EGNOS, North America's WAAS and OmniSTAR
(VarioGuide functions with VBS and HP).
• terrestrially with a base station or RTK network.
3.1.2 Satellite reception
• The GNSS signal and the correction signal may
be obstructed by dense trees, copses,
buildings, high-voltage power lines etc.
Fig. 1
• VarioGuide loses the correction signal when the
correction signal satellite is less than 5 to 8
degrees above the aerial level.
NOTE:
The correction signal satellite is geostationary
above the equator.
Fig. 2
3. VarioGuide definitions and specifications
VarioGuide 21
438.020.070.012