PPP-Wizard: Precise Point Positioning With Integer and Zero-difference Ambiguity Resolution Demonstrator

The PPP-WIZARD demonstrator is a 'proof of concept' of the zero-difference ambiguity resolution method developped in the orbit determination service at CNES.

One can find all the details on this method in the publications available in the links page.

This method can be applied to the precise positioning in real-time using GNSS measurements and allows to obtain a centimeter accuracy positioning. Its advantages are the following:

  • The precision is about one order of magnitude better than the standard PPP methods (1 cm RMS vs 10 cm RMS).
  • It does not need a reference station, unlike local methods like RTK
  • It can be applied globally, with a very low additional required bandwidth, compared to PPP. In particular, this bandwidth is comparable to what is used in SBAS systems or will be used for the Galileo Commercial Service (below 500 bits/sec).
  • It is  well suited for isolated areas, where no reference station is available.
  • It is NOT a regional augmentation method. In particular, it does not estimate atmospheric parameters and does not need a dense network of stations.

This demonstrator is built around 3 parts:

  1. The 'SSR computation' part, which consists in the computation of orbits and clocks of the GPS and GLONASS satellites, in a state space representation. This is a representation that uses a very low bandwith for broadcast corrections. This part is by far the more complex one. It uses a global network of real-time GNSS stations.
  2. The broadcast part, which consists in the transmission of the orbits and clocks to the users, using a predefined protocol and standard. This part uses the  IGS caster.
  3.  The user part, called 'PPP Monitoring', which along orbits/clocks and measurements of a receiver, performs precise positionning with integer ambiguity resolution in real-time, as well as the comparison with an absolute reference position, to analyse the quality of the broadcast solutions. For this purpose, the PPP module is limited to stationnary receivers.

The following figure shows the overall architecture of the demonstator: