Fundamental of GNSS

• GNSS Consists of


  • GPS
  • Glonass
  • Galileo
  • Beidou
  • SBAS
• SBAS


  • Function is to enhance the Basic systems above and the primary objective is for navigation safety
  • WAAS
  • EGNOS
  • MASAS
  • GAGAN
• GPS-Glonass


  Outcome of differences of capabilities and outcome for precision but Glonass so far has 9 Satellites operational
• Galileo


  • Truely a system of innovations that their objective is more with the safety of public in navigation and transport systems –benefit of Institutions and Organisations
• Common Attributes


  • Satellite Components
  • Ground and Geosystem Control Stations
  • User Segment
• GPS Signal Frequencies


  • L1 on 1575.42 Mhz
  • L2 on 1227.6 MHz
  • L5 on 1176.45 MHz
• GPS has L3 and for Atomic Bomb detection and also adding the L5 for safety in the modernisation program
• Galileo is almost like GPS but compared to GPS is the implementation of global/regional segments for integrity monitoring
• Galileo Objective


  • To assist the Safety critical aircraft navigation, locate and guide railway trains operations
• ECEF (Earth Centred, Earth Fixed) Geocentric System


  Relationship with the Geographic System Lat, Long and Height
• Galileo Refers to Galelio Terrestrial Reference Frame (GTRF) similar to ITRF
• GTRF and WGS84 differ by few cm
• Glonass- PZ90 Coordinate System ITRF of WGS84 System and on ECEF system
• IERS does the transformation of the system
• Observation Techniques


  Measure the difference of time travel from the satellite to the receiver to compute location and time
• Signal Frequencies


  • Code Pseudorang Measurments for very basic Receivers- Standalone
  • Phase Pseudorange for High Precision Receivers
• System Observable Errors


  • Satellite Clock Errors
  • Orbit Errors (Satellite Drift)
  • Ionospheric
  • Tropospheric
  • Receiver Clock
  • Multipath
• GNSS Positioning Techniques


  • Single Point Positioning
  • Differential Positioning