Hi Kirk,
OK, I'll rule out the PPP for now, although it doesn't seem to be
practical for production mapping anyway.
I think my antennas are probably OK, none of them have a ground plane,
not practical for field mapping. I've only seen them in geodetic
applications. Of course, the aircraft installation is free of multipath
except while on the ground. Longer observing periods should minimize
the impact of multipath zingers.
The tight clustering of the GeoXT points in Map A doesn't smell of
multipath to me.
Earlier you noted the possibility of antenna shielding by the operator.
With that in mind, I use a tripod or a range pole with the antenna above
head height. WAAS is actually quite accurate, good for certain (lower
order?) precision approaches.
I'm still digesting all this helpful feedback and will work on a summary
shortly. Thanks again . . . .
-----
Cheers, Spring
On 09/Mar/2021 12:14, Kirk Schmidt wrote:
Hi Springfield:
PPP requires long observation times in the order of hours and
therefore a new field survey. I would try post processing from a high
precision site with your existing data.
Another issue may be the aviation antennae you mentioned. These are
usually mounted on the top of a fuselage and therefore the aluminum
acts as a ground plane to effectively filter out multipath. If you
use a metal disk or plate and a ground plane on your antennae and
mount it on a tripod, you may find you end up with better results.
You will notice survey grade antennae's have a large diameter plastic
case since the contain an internal 10 cm metal disk.
Kirk Schmidt
On 3/9/2021 1:36 PM, Springfield Harrison wrote:
Hello Garth,
Thanks very much for that reference. I have used the service in the
past.
I'm in the middle of other work but may try to re-process some Map A
files using PPP to see what changes.
Your work sounds more like surveying than mapping, interesting.
I do use the GPS reception planning tools but SV availability is
certainly better than in the early days.
Thanks again . . . .
-----
Cheers, Spring
On 09/Mar/2021 09:01, Garth Fletcher wrote:
Nicolas Cadieux wrote:
Kirk could be on the right track. You could try PPP using this
site. You will need to create a user name and password. Then, you
upload the Rinex file. I am 99% sure you can process point from
outside of Canada.
I routinely use CSRS PPP to post process RINEX files from Southern New
Hampshire (43°N, 72°W).
Using an iGage iG3s (L1/L2 dual frequency, GPS + GLONASS) recording at
5 second epochs in forested areas, from post processing I get
30 minute recordings, 95% error ellipses < 1 meter
10 hour recordings, 95% error ellipses < 2 cm
CSRS-PPP site is
<https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php?locale=en>
enter your email address
select Static and which NAD 83 epoch you want, or ITRF
Submit a RINEX file (.zip compressing the file is encouraged)
they will email back a detailed report
You can submit for 1 of 3 levels of post processing
ultra-rapid : submit > 90 minutes after end of recording
rapid: submit > 24 hours after end of recording
final: submit ~ 3 weeks after end of recording
Major part of corrections are in ultra-rapid, the higher levels provide
further refinements.
FYI: Trimble provides occupation planning aids at
<https://www.gnssplanning.com/#/charts>
just enter your location and date and it shows you the DOP as
a function of the hour of day.
Cordially,
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