GNSS data processing strategies
There are multiple strategies to process GNSS raw measurements in order to obtain the position. The most common ones are:
- Single Point Positioning (SPP)
- Precise Point Positioning (PPP)
- Real Time Kinematics (RTK)
- Post-processing Kinematics (PPK)
With the advent of new constellations and the inflationary number of additional signals and frequencies (between the original L1 and L2 from GPS) as well as the requirements of convergence time in dynamic scenarios, new techniques based on innovative data models (such as undifferenced and uncombined processing) or a combination of classic techniques (PPP-RTK) are gaining relevance in front of these.
| strategy | needs base? | uses carrier-phase? | orbits & clocks | accuracy |
|---|---|---|---|---|
| SPP | no | no | broadcast | < 5 m |
| PPP | no | yes | precise | cm (multi-freq), dm (single-freq) |
| RTK | yes | yes | broadcast | cm (multi-freq), dm (single-freq) |
| PPK | yes | yes | broadcast | cm (multi-freq), dm (single-freq) |
- needs base? implies if the technique is a differential technique (requires the provision of GNSS data from a base station with known coordinates)
- uses carrier-phase? the carrier-phase is required to achieve decimeter or centimeter accuracy.
- orbits & clocks which type of orbit and clock products does the technique require.
- accuracy is a ballpark indicator of the accuracy that can be achieved for the strategy.
Besides the technique to process data itself, one can inform the filter wether the rover moves (dynamic) or stays still (static). This can be configured in Virtual-lab: select only static if you are sure the receiver was not moving during the data campaign, otherwise leave the default, which assumes a moving (dynamic) rover.
Finally, please consider that the number of frequencies tracked by the receiver might be crucial in terms of performance. For standalone techniques (SPP, PPP), which do not require base station, tracking 2 or more frequencies will allow to remove the ionosphere error, leading to greater accuracies. In general however, and this is valid for all strategies, tracking multiple frequencies will provide not only better accuracies but also increased level of robustness and faster convergence times.