In my last post, I demonstrated some PPP solutions using real-time SSR corrections from the CLK93 data stream with various dual frequency receivers. Results were quite good with errors after four hours generally below six centimeters in each axis.
Many of my experiments are done using RTK solutions with short baselines where the differences between dual frequency receivers and single frequency receivers can be fairly small. With PPP solutions however there are significant differences between single frequency and dual frequency receivers. This is because the ionospheric errors increase with increasing baseline and the dual frequency measurements are much more effective at coping with these errors.
To demonstrate this, I duplicated the previous experiment with a single frequency receiver, collecting twelve hours of raw observations with a u-blox M8T receiver along with the CLK93 real-time data stream for SSR corrections. I processed the data with the same configuration settings as last time, except using “L1” instead of “L1+L2” for frequencies and ionospheric corrections set to “broadcast” instead of “ionospheric-free” (dual-freq) corrections.
As expected, the errors, even after 12 hours were fairly large. Here is the result. Even after 12 hours, the vertical error was nearly two meters.
Presumably the single frequency PPP/SSR results will improve if RTKLIB is extended to support the RTCM SSR Phase 2 and Phase 3 ionospheric correction messages.