Hi, all Not sure if this is 100% within scope of the list, but still: I am trying to get some good stability measurements of my hydrogen maser, using GPS L1/L2 and PPP. I collect L1/L2 code and phase observables continously, and process daily RINEX-files with PPP software and IGS corrections. I've used the NrCAN-PPP online service, which gives reasonably good results. The issue with NrCAN is that it only process in the forward direction (at least, this is what I assume, looking at the results.) So I want to run the processing locally so that I can run it both forward and reverse. I have not been able to get a copy of the nrcan-ppp softwarepackage, so I am looking elsewhere. ESA gLAB looks like it might fit the bill. The problem, in short, is that the data I get from postprocessing with gLAB is much, _much_ noisier than the results I get from submitting the RINEX files to NrCAN-PPP online service. (see attached screenshot - note I've cut away the first 2-3 hours of noisy data from nrcan) I've tested this on both a Trimble NetRS and a Novatel OEMV3, and I get comparable results from both: nice smooth data from NrCAN (except the first 2-3 hours), jagged noisy data from gLAB. (The Novatel required jumping through MANY hoops before I could get any usable data, including writing a RINEX-converter. In case someone wants to play along..) I'd be tempted to think NrCAN applies smoothing somewhere, but the .sum file contains "Parameter smoothing: NO" I am running gLAB with 5-second interval observations, IGS Rapid products (*.sp3, 10 degree clock interpolation), forward/reverse, throw away the forward, grab clock offset from the FILTER output, convert to ns - as A. Wallin is doing in ppp-tools. So, in summary; does anyone know what is going on? Am I missing some step in the gLAB processing? Thanks for any insight. Ole [image: Inline image 1]

> I have not been able to get a copy of the nrcan-ppp softwarepackage, so I > am looking elsewhere. ESA gLAB looks like it might fit the bill. The > problem, in short, is that the data I get from postprocessing with gLAB is > much, _much_ noisier than the results I get from submitting the RINEX files > to NrCAN-PPP online service. > Hi Ole! I did a comparison of a few PPP results some years ago, maybe you saw it already http://www.anderswallin.net/2013/12/comparing-gps-ppp-solutions/ For the web-service running NrCAN, there was an URL API that allows running the filter/algorithm forward and backward ("filtfilt" in matlab or numpy), to get rid of the initial transient in only the forward solution. You could ask the maintainers, or I can try to dig in my archives (I should have python code that submits RINEX to the service and retrieves the results). >From my link above it looks like the troposphere-models are quite different. Here is a recent ".sum" summary file from a NrCAN run: https://pastebin.ca/3816315 in section 2.7 it has the troposhpere model type, and in section 3.1 a parameter "TZD random walk (mm/hr): 5.000" if you dig in the ESA gLAB settings, can you set the ZTD-model identically and see what happens? If you post your RINEX:es and other relevant data I can try processing also and see what I get. cheers, Anders

> > I did a comparison of a few PPP results some years ago, maybe you saw it > already > http://www.anderswallin.net/2013/12/comparing-gps-ppp-solutions/ Ah, yes I forgot about that! Nice, I'll revisit RTKlib again. > For the web-service running NrCAN, there was an URL API that allows running > the filter/algorithm forward and backward ("filtfilt" in matlab or numpy), > to get rid of the initial transient in only the forward solution. You could > ask the maintainers, or I can try to dig in my archives (I should have > python code that submits RINEX to the service and retrieves the results). > That could be an option, I will contact the maintainers. if you dig in the ESA gLAB settings, can you set the ZTD-model identically > and see what happens? > I will investigate the TZD-model, thanks for the tip. I was trying to wrap my head around differential code biases; It seems NrCAN PPP applies corrections, but I believe gLAB does not by default (and it crashes when I give it -model:dcb:p1c1 strict). Not sure if DCB would show up as an issue at the level I am looking at now, though. If you post your RINEX:es and other relevant data I can try processing also > and see what I get. Appreciate the offer! :) Link to a recent RINEX that gives a reasonable result from NRcan PPP: https://www.dropbox.com/s/er9o6lfg4gva486/2017.05.21.zip?dl=0 Thanks! Ole