Understanding GPS-GNSS. Michael Buschermohle Precision Agriculture Specialist UT Extension. Global Navigation Satellite System (GNSS). Satellite Systems. GNSS = GPS + GLONASS + future additional satellite systems. Global Positioning System (GPS): 24 Satellites ( USA)
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GNSS = GPS + GLONASS + future additional satellite systems
Global Positioning System (GPS): 24 Satellites (USA)
GLONASS : 18 Satellites (Russia)
Galileo: 2 Satellites (European Union)
Need 5 satellites to maintain RTK-fix
Satellites broadcast several pieces of information
Sources of GPS Error
Let’s put some numbers on it
Altitude = 12,500mi.
Speed of light = 186,000 mi/sec
Transmission Time = 0.067 sec
What happens if we are off a little?
0.001 sec * 186,000 mi/sec = 186 mi
Ephemeris (Orbital) Variation
University of Tennessee Extension
Good (low) DOP
Poor (high) DOP
Satellite-Based Differential GPS Correction
Real-Time Kinematic (RTK) GPS Correction
Virtual Reference Station
Continuous Operating Reference Station (CORS)
Courtesy of Fulton, Auburn University