[Qgis-user] Trimble GeoXT 2005 Accuracy

[Springfield Harrison]

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,
>> _______________________________________________
>> Qgis-user mailing list
>> Qgis-user at lists.osgeo.org
>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>