Hans Mayer <[email protected]> writes: > sorry for this off-topic message, but maybe it's for interest for somebody > else.
totally on topic! > As you know I did some measurements and I was interested how the results are > distributed. > Below you see blue, red and green dots in the graph. > The blue one are measurements with averaging each done over 24 hours. I have > done this about 2 years ago. > The red I have done with gpsrinex and sent to CSRS-PPP at Canada immediately > when the run was done. Sent some weeks ago. > The green are identical to the red but sent 2 weeks later a second time to > Canada. ( Final ) I suggest that you convert to UTM or some such so the plot is in meters. Also, I suggest that you plot on paper at 1:1. A friend did an experiment measuring a geodetic monument multiple times over multiple days (using RTK with MaCORS, not gpsd -- now that's off topic!), and plotted the obtained positions and the published position. He plotted these on graph paper at 1:1 scale, so that 10 mm on the ground was 10 mm on the paper. A radical choice! It really gave a good perspective on how tight the MaCORS-derived positions were and how the official position was consistent. Before you do this, I suggest you clean up 1, maybe two things. The first is that you should make sure you are using the same datum. Positions from gpsd, if using EGNOS (guessing you are in .at), are in the frame of EGNOS. That's a harder question than you might realize. See page 20 and onwards: https://www.euspa.europa.eu/sites/default/files/brochure_os_2017_v6.pdf If not using EGNOS, then it's WGS84. With CSRS-PPP, they have mulitple offerings and you didn't specify. After that, if you are using a dynamic datum (Egnos TRF, ITRFnn, WGS84), or a static datum on the wrong plate (NAD83 in EU), then you need to bring positions to a common epoch to compare them. > The most interesting question is "what is the distance?" The maximum is about > 80 cm ( 2,6 ft ) I don't find that super interesting because I don't expect accurate answers from averaging GPS. I do find the rapid->final CSRS coordinate shift interesting (guessing at pairs, would be cool to draw lines). And the clustering of the 4 PPP results. It would be nice to also show some kind of error bounds on each. I suspect that showing error bounds will point out that the error bounds are not credible.
