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Re: ✘PX1172RH_DS performance
Gary E. Miller
Re: ✘PX1172RH_DS performance
Wed, 6 Apr 2022 13:56:27 -0700
On Wed, 06 Apr 2022 16:17:53 -0400
Greg Troxel <email@example.com> wrote:
> > 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.
So much that I don't know. My current plan for this summer is to do
a whole day on top of a USGS monument.
> >> 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.
Still only makes sense if I do a lot of things that use the calibration
files, like PPP. Which I do not. Yet.
> >> 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
Maybe they do, but their RTCM3 broadcasts that they use the "NULL"
> The APC is usually a few cm higher than the ARP, so you need
> to take that into account to get cm-level heights.
hard to be a few CM higher when the entire height of the anteann
case is on 2 cm.
> >> > 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.
Maybe to you. Not to us near the middle of nowhere.
> 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?
Yup. OPUS does not fail, they refuse to even try.
> >> > 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.
Then your expectations are off.
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
firstname.lastname@example.org Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can't measure it, you can't improve it." - Lord Kelvin
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