PPP solutions with SSR corrections for a single frequency receiver

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.


4 thoughts on “PPP solutions with SSR corrections for a single frequency receiver”

  1. RTKlib 2.4.2 supported Rtknav real-time single-frequency PPP correction with the u-blox M6T, which I recall might also have needed an RTCM3 correction from an NTRIP or other correction station.

    Sadly, Rtklib 2.4.3 does not appear to support single-frequency PPP anymore. I can understand that 1-2 meters of ionospheric error over time is horrible, however if WAAS and/or RTCM3 could partially correct for this and the single-frequency receiver were run in a PPP (Phase-based) position for several days, it might just be possible to resolve sub-meter accuracy from a single frequency receiver.

    Before someone retorts with why not just use RTK if you have an RTCM3 correction already, well that correction station might be too far away at 20+ km to resolve an RTK fix or you might not trust the ground truth or altitude of the correction station, especially if you don’t know the added height of the GNSS survey antenna installed at the reference station.


  2. The internal Ublox solution might actually give a better result.

    I’m guessing it won’t matter much, but can you use SBAS corrections (Tropo/Iono) with SSR corrections and the Ublox receiver?

    I doubt single frequency PPP will ever amount to much. When you dig into the details like in the GEO++ SSR reference you’ll see they talk about 30 cm (1 sigma) accuracies with “state of the art” single frequency receivers. Even if a simple Ublox receiver is used to get similar accuracies often a high end antenna costing a lot more than the receiver is used. With the announcement of several presumably low cost multiple frequency chips hitting the market over the next several months single frequency technology is probably going to fade for anything considered high accuracy.


    1. Hi JB. In theory you should be able to combine the SBAS atmospheric corrections with the SSR oribital/clock corrections but I believe there is a bug in the present RTKLIB code that prevents using SBAS corrections with single frequency PPP solutions.


  3. Thanks for publishing your experiments with SSR corrections. I’m very curious to see how useful SSR turns out to be for consumer-level GPS devices. I understand that it’s possible to use SSR data to compute RTCM corrections that could be used by receivers like the uBlox M8P. Is this something you think you might experiment with?


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: