System and method for augmenting DGNSS with internally-generated differential correction
In the invention, a rover receiver first utilizes data from a base Receiver, a DGNSS reference network, or other differential source to compute a differentially corrected location. Then, using this location and data observed only at the rover, the rover computes an internal set of differential corrections that are stored in computer memory, updated as necessary, and applied in future times to correct observations taken by the rover. The possibly mobile rover receiver, therefore, corrects its own observations with differential corrections computed from its own past observations; relying on external differential for the sole purpose of establishing a reference location, and this is unlike prior art.
1. A method of computing differentially corrected global navigation satellite system (GNSS) measurements within a rover receiver in a GNSS system including a base receiver, which method comprises the steps of:
at the rover receiver, observing code and carrier phase GNSS signals from first and second satellite sets;
at the rover receiver, either: 1) receiving from the base receiver GNSS signal observations and a GNSS-defined base receiver location, and computing first satellite set differential corrections; or 2) receiving from the base receiver first satellite set differential corrections;
storing said first satellite set differential corrections in computer memory in said rover receiver;
receiving at the rover receiver at a first instant of time (Time 1), first satellite set measurement information;
computing in the rover receiver at Time 1 a differentially-corrected location for the rover receiver using the first satellite set measurement information and the first satellite set differential corrections;
observing at the rover receiver, at Time 1, second satellite set measurement information;
predicting geometric ranges for the second satellite set using the differentially-corrected Time 1 location computed by the rover receiver;
computing second satellite set differential corrections based on said predicted geometric ranges for the second satellite set minus the observed second satellite set measurement information;
observing at the rover receiver at a second instant of time (Time 2), second satellite set measurement information; and
computing, at Time 2, the rover receiver's location using the second satellite set differential corrections and the Time 2 second satellite set measurement information.
2. The method of claim 1 , which includes the additional step of:
solving for integer ambiguities in said second set of satellite measurement information.
3. The method of claim 1 wherein GNSS satellite measurement information is received by said rover receiver from one or more of the group consisting of: GPS; GLONASS; Galileo; Compass; a satellite-based augmentation system (SBAS); a regional satellite system; the wide-area augmentation system (WAAS); a transmitter located on or near the ground; and a pseudolite.
4. The method of claim 1 wherein said GNSS satellite measurement information contains one or more of the group consisting of: a phase; and a pseudorange.
5. The method of claim 1 wherein said differential enabling data contains one or more from the group consisting of: a differential correction; clock correctors; orbit correctors; a pseudorange; and a phase.
6. The method of claim 1 wherein said communication link is to one or more of the group consisting of: a base station; an SBAS satellite; an Inmarsat satellite; and a network RTK source.
7. The method of claim 1 , which includes the additional step of:
updating the second satellite set differential corrections based on the Time 1 minus Time 2 variation from the first satellite set differential corrections.
8. The method of claim 1 , which includes the additional steps of adjusting the second set of differential corrections for:
modeled atmospheric changes; and
orbit/ephemeris parameter changes.