Re: ✘PX1172RH_DS performance

[Greg Troxel]

"Gary E. Miller" <gem@rellim.com> writes:

>> OK on RCC-261-00 but there is still an important difference between
>> spread relative to average and spread relative to the correct answer.
>
> Where do I find ground truth for 7mm, when my local CORS wanders over 1cm
> in each direction?

If you get position a different way and it's within 1 cm of the average,
you call that great.  But until you compare you don't know.


>> >> I am 99% guessing
>> >> that you don't have a mm-level position for the APC,
>> >
>> > Uh, what is APC?  
>> 
>> Antenna Phase Center.  The physical location whose position is
>> actually determined by a GNSS receiver in the most straightforward
>> setup.  On better antennas, this is specified relative to an Antenna
>> Reference Point (ARP), which is something you can physically access
>> to measure. Typical ARP is horizontally the center of the 5/8 thread
>> and the vertically "Bottom of Antenna Mount".
>
> Oh, yeah.  I can'f afford those antennas.

This one is under $200; it's the low end of calibrated.
  
https://www.ardusimple.com/product/calibrated-survey-gnss-multiband-antenna-ip67/

>> Getting more hard-core, there are antenna calibration files and the
>> APC varies with satellite elevation and sometimes also with azimuth.
>
> Even ORGN is not that hard core.

I find that very surprising.  I would expect that the reference stations
are using something like Leica or Trimble and have calibrated antennas
and are using ANTEX cal files in their base setup.  The APC is usually a
few cm higher than the ARP, so you need to take that into account to get
cm-level heights.

> When I get around to doing a PPP from the current setup, compare it with
> other PPP on the same location, code up new plots, etc.
>
> So much to do, so little time.

Sure.


>> >>   raw observations for 24h (same bits) and use OPUS
>> >
>> > OPUS is not available where I live.
>> 
>> Really?   OPUS takes raw L1/L2 files and calculates positions based on
>> NOAA CORS Network stations.  I am 99% sure it works anywhere in CONUS.
>> Maybe they are too far away to get really good positions.
>
> There is only one CORS station within 100 miles of my position.  Not
> enough for OPUS to try to do a PPP.

That's surprising.   But OPUS does not do PPP.  It does carrier phase
differential.   Are you saying that you took a L1/L2 24 hour raw file in
RINEX and you can process that with NRCAN PPP but if you submit to OPUS
it fails?

>> > Thus the need for the roof mount.  Which makes it not very practical
>> > as a mobile application.
>> 
>> I haven't tried it on a car yet, but walking around in places without
>> a lot of trees works well, with MaCORS.
>
> But you have an F9P, and this is a PX1172RH_DS.  Apples and organges.

They are basically the same architecture: dual-frequency with RTK code.
I would expect similar performance.

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