RTK (Real-Time Kinematic) and PPP (Precise Point Positioning) are two well-known technologies in GNSS positioning that have been developed over decades.
RTK (Real-Time Kinematic) and PPP (Precise Point Positioning) are two well-known technologies in GNSS positioning that have been developed over decades. In RTK positioning, the rover station obtains simultaneous observation data from the base station or CORS for double-difference ambiguity fixing, so as to quickly achieve high-precision real-time positioning.
However, RTK positioning technology is limited by the communication link for correction data transmission and the distance between the rover and the base station (or the coverage of the CORS network), resulting in a lack of operational coverage.
PPP positioning can directly achieve high-precision positioning by using a single GNSS device, breaking through the limitation of the operating range and greatly increasing the flexibility of the device’s use, while it takes a certain amount of time to converge to obtain the results of PPP-AR (Precise Point Positioning with Ambiguity Resolution).
With the rapid development and iteration of high-precision real-time positioning technology, both RTK and PPP have been applied in many fields, such as autonomous driving, intelligent agriculture, UAV, marine positioning and other emerging industries. According to the characteristics of RTK and PPP, the appropriate positioning technology should be selected. The reason for the difference between RTK and PPP lies in the difference in their positioning methods.
How GNSS Positioning Errors Are Eliminated
The essence of GNSS high-precision positioning is a process of eliminating errors in GNSS positioning. In terms of the sources of GNSS positioning errors, the single-point positioning of a GNSS device includes satellite-side orbital errors, clock errors, satellite bias, the effects of the ionosphere and troposphere on the propagation path, and receiver-side errors.
RTK Positioning
In RTK positioning technology, the observation data of the base station or the virtual base station calculated by a CORS service is transmitted to the rover station through radio, network and other communication links. Centimeter-level positioning is then realized by eliminating satellite-side error and propagation path delay through the double-difference calculation of observation data from the base station and rover station.
PPP Positioning
The idea of eliminating error in PPP positioning technology is completely different. For satellite-side orbit error, clock error, bias and other errors, the GNSS device directly receives ORB, CLK and other data broadcast from the satellite to eliminate these errors. It then uses UPD (Uncalibrated Phase Delay) phase fractional deviation estimation and other methods to achieve PPP ambiguity resolution and ultimately obtain high-precision results.
Operational Differences
From the two methods above, it is not difficult to find that the correction-data transmission communication link is crucial in RTK positioning technology.
If the rover station is in the vicinity of the base station and the communication link is smooth, the RTK positioning effect is best. PPP positioning technology directly receives positioning error correction data from the satellite side, so it no longer communicates with the base station and does not need to focus on the distance from the base station.
The two are a bit like the daily use of smartphones through a ground base station to obtain 5G network signals, compared with connecting to the Internet directly through Starlink.
Tersus TAP
As a leading high-precision satellite navigation professional enterprise, Tersus has recently launched TAP, a satellite-based rapid convergence service under PPP positioning technology. This also means that Tersus GNSS boards or receivers can achieve both RTK positioning technology and meet the requirements of PPP positioning technology, realizing high-precision positioning requirements in different scenarios.
