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.
