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The orbital correction provided by ntrip.itsware.net (how to use it in RTKNAVI) #365

Open monsak opened 6 years ago

monsak commented 6 years ago

I found that ntrip.itsware.net is providing a real-time Ephemeris correction and would like to use it to correct my coordinate solution from RTKNAVI.

I search the Internet and tried multiple settings in RTKNAVI/RTKLIB but cannot make that work so far. Questions

  1. Am I correct that the real-time Ephemeris correction from ntrip.itsware.net can be used as a correction source in RTKNAVI?
  2. If so, how can I use it? Below are what I tried . 2.1 Input RTCM3EPH as a correction (a type of input streams) in RTKNAVI. 2.2 Apply the positioning method method PPP Static, PPP Kinematic, and PPP Fixed. Both does not seem to improve the positioning solutions at all.

You guys can try the real-time Ephemeris correction using the information below. ntrip.itsware.net port 2101 mount point RTCM3EPH

DavidKelleySCSC commented 6 years ago

@ monsak: That stream "RTCM3EPH" is just a set of all broadcast orbits from all GNSS systems. You can get it from several places, including the NTRIP.use-snip.com:2101 and the RTK2go.com:2101 Caster sites. It in fact comes from products.igs-ip.net (God bless the folks at IGS!) and the SNIP Casters are just repeating it. It will not "correct" anything in that regard.

Here are its message contents. bcastorbits

But what you need for PPP is the precise orbits and clocks, which are issued as corrections (SP3 format) to the above broadcast data, And you need L1+L2 signals (so a uBlox devices would not suit as I understand RTKLIB today, hope I am wrong on that). Read the RTKLIB manual for details and data sources. Make these the "corrections" input-3 on Navi.

Here is a fragment taken off the SNIP knowledge base page that may point you the right way.

These two articles provide a very good job of explaining the issues and mention which RTCM message are used for various needs. Keep in mind that you need to be sure what reference frame is being used with the different orbital data feeds as well. http://www.igs.org/rts/products https://igs.bkg.bund.de/ntrip/orbits

We run this stream for our own needs, where we are often combining it with an RTK base station in the hopes that the Rovers will fair better when the correction streams drop off for periods of time. You are free to use this or connect to the above source directly. clkproducts

You can also 'trick' NAVI by loading up the current Bcast orbital data and then changing the process corrections stream. Or you can make the Bcast orbital data input-2 and then use the precise data as input-3. Again, you need an L1/L2 set of observables, use any Base Station you want as input-1 to get some if you do not have a suitable rover device. Hope this helps.

rinex20 commented 6 years ago

RTCM3EPH is a broadcast-grade ephemeris, not precise.It is the same as the broadcast ephe received by your rec.