[FOSS-GPS] first steps with RTK and RTKPOST

Felipe G. Nievinski fgnievinski at gmail.com
Fri Nov 27 07:13:41 PST 2015

> - the quality flag, Q, is set to 5: Single, solution by single point
> positioning.
> Shouldn't it be equal to 1 or 2 ?
for some reason it's not doing relative positioning with respect to the
base station.  try enabling debug information in one of the tabs in
rtkpost, then check the output files for warnings.

- I wonder why, in the input of the rinex observable file, we can't select
> many files ? (same question for rinex navigation file)I mean, I can have
> many files, each one from a different permanent GNSS base station. Do I
> have to merge those files before processing in RTKPOST ?
rtklib does one base station at a time.
you can try different bases in different runs.

other software are capable of merging the results
from multiple baselines as a weighted average.

> - In my results, I get a gap of around 5 meters, in comparison to my RTK
> gps track log without post processing. This looks to me as a very important
> gap. I can't say if the result is better, but is it possible to get a so
> important gap between RTK with and without postprocessing?

do you mean a shift or offset in coordinates?
well, as you said, your "base is not installed on a known point."
you should find a similar 5-m difference
processing your base with respect to the
permanent base station -- do it in static mode.

In my rinex observable file from the rover , I had 1 and 1 for WAVELENGTH
> FACT L1/2, that's enough to ensure RTK mode had really worked ?
please ignore those records, that's just weirdness of some receivers.
see rinex file format specification if you're curious.

> - Also I have noise, on the post processed track log. Small noise : around
> 10 cm for 0.3 second for example, but this noise does'nt exist on my RTK
> gps track log without post processing.

not sure what's the 0.3 sec you mention.
is the 10 cm a sporadic spike or intermittent scatter?
try sending a figure/plot.

And the change of ionosphere correction to Iono-Free LC didn't successed to
> remove the noise. How can I remove the noise ?
how far is the permanent base?
if it's less than 10 km, don't use I-F.

I heard that PPP solution is not suitable for my configuration as the
> solution as no time to convert, the flight is too short. If you have any
> comments about this, there are welcome.
20 min might be enough to converge
with a dual-frequency receiver...

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