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I am looking for a positioning accuracy that is higher than normal consumer-grade GNSS receiver (mostly GPS/GLONASS hybrids with +- 5m precision). I came across RTK with dual receiver setup (base station + rover) which is supposed to do cm-level precision although it has the "disadvantage" while it needs a base station or another source of correction data that one may not be able to supply.

I am interested in getting the most of a single receiver setup. I read Precise Point Positioning (PPP) is able to achieve sub-meter (or maybe even 20cm-level) accuracy. I think PPP needs raw data from sensor which I can do. I will do readings from a moving vehicle in my application so I can not go with stationary "averaging" over time for getting the accuracy. However, I do not need a real-time solution as I will only collect mobile data and evaluate it later so I can do positioning in post-processing.

U-blox also has a page on PPP where I get the impression their solution is just an ordinary raw data chip with a "better firmware" that can do some additional calculations (quote: "... by stabilizing measurements of the distance between GNSS satellites and the receiver (pseudo-ranges) using carrier phase tracking") so it has better precision than ordinary chip.

I read the Wikipedia article but I do not really understand how PPP works. So how exactly is this PPP correction technically done? Where do the corrections come from?

I read RTKLIB can do PPP too. My location is Czech Republic.

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PPP relies on post-processing using precise orbit and clock data from the satellites. This is data for the same timespan as your measurements, and is based on logged information from reference stations. If you require on-the-fly positioning I doubt you can use PPP.*

Depending on your location there may be correction services available where you instead of a base station retrieve corrections from reference stations by radio or telephone. For the Czech rep., take a look at CZEPOS

One-Centimeter Accuracy with PPP: The Future of Satellite Navigation from Inside GNSS seem to give a thorough run-through of the method.

*It seems you can get real-time data as well, based on broadcasted data, as announced in GPS World under the title IGS Launches Real-Time Service. This would presumably not be as accurate as post-processed data.

  • Thx for answer. My location is Czech Republic. However, I do not need a real-time solution as I will only collect mobile data (stereo imaging) and evaluate it later so I can do positioning in post-processing. I edited my question accordingly. I also would like to avoid streaming (or downloading for post) any correction data at all as this is not available everywhere around globe... not a convenient solution for a global community project. I am just wondering about the best possible accuracy for an offline single receiver without 3rd party correction data. – Kozuch Sep 4 '14 at 9:17
  • "using precice orbit and clock data from the satellites" - so does this mean for PPP you have to supply data from reference GNSS base station(s) or where can one get the corrective data? – Kozuch Sep 4 '14 at 9:24
  • To get the corrections you will need "someone" to log data from know reference station. The main point with the method of PPP is that you don't need to have your own reference staion, as the data are global. I think you should be able to get data from e.g. IGS – HavardMoe Sep 4 '14 at 9:25
  • Ok, I see. For two receiver RTK you need a base station possibly close to your rover station, but for PPP the corrective data are global, so a single ref station anywhere in the world is enough. This seems to make PPP have a greater "value for money" if you dont really need cm-precision... – Kozuch Sep 4 '14 at 9:38
  • It depends on what you want to achieve when it comes to accuracy, I guess. You could threoretically manage with one ref. station, but you would get better results using multiple station and preferraby not too far away (i.e. in your country) to make sure you get the corrections for athmospheric distortions etc. – HavardMoe Sep 4 '14 at 9:47

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