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Limitations of existing systems
 
The existing systems (GPS and GLONASS) have four major limitations preventing their use in applications such as civil aviation where safety is a high priority. These are:
  • lack of integrity
  • lack of availability and continuity of service
  • lack of accuracy (for critical phases of flight)
  • no control by an international civil body

 
 
Reasons for inaccuracies in existing systems
 
With the existing systems there are also four possible sources of errors, these are:
  • Satellite errors
    Errors with the satellite signal due to clock and orbital uncertainties
  • Atmospheric errors
    Delays with the signal propagation through the atmosphere (ionosphere, troposphere)
  • Receiver errors
    Errors on the computed user position due to the receiver's technology
  • Environmental errors
    Perturbation with the satellite signals due to the local environment of the user. These could be caused by reflections, surrounding buildings or interference.
     
     
    Last update: 9 November 2001
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