[Qgis-user] Trimble GeoXT 2005 Accuracy

[Springfield Harrison]

Hi Kirk, thanks for your comments.

Note that the unit is not a Garmin.

My concern is not with the accuracy /per se/ but the systematic 
displacement of the results.  GPS error is usually "random", at least 
over the longer term.

The unit was kept static, 50-60 positions were averaged over 4+ minutes 
and the correction was real time SBAS.  The two readings per site were 
separated in time, code based only.

I've since deferentially corrected the file, results yet to be reviewed.

In a later post, Greg refers to datum issues which I think might be the 
culprit.

Thanks very much . . . .

-----
Cheers, Spring



On 06/Mar/2021 03:36, kirk wrote:
> That is the limitation of the unit you have. Without using 
> differential correction or real time kinematic techniques, that is 
> about as good as it gets. You can improve your position a bit by 
> keeping the unit static and averaging the 1 hz position data for at 
> least 2 minutes. This will give you an average of >120 observations..
> A clear view of the sky we also help improve the accuracy.
>
> For post processing work, you will need  unit that records raw rinex 
> format data which ghe garmin units typically do not.
>
> Kirk Schmidt
>
>
>
> Sent from my Galaxy
>
>
> -------- Original message --------
> From: Springfield Harrison <stellargps at gmail.com>
> Date: 2021-03-06 4:35 a.m. (GMT-04:00)
> To: qgis-user <qgis-user at lists.osgeo.org>
> Subject: [Qgis-user] Trimble GeoXT 2005 Accuracy
>
> Hello All,
>
> I recently acquired a Trimble GeoXT 2005 Series and am puzzled by the 
> results it produces:
>
>  1. Compared to a variety of "known" points, it consistently records
>     positions that appear to be in error by 1.2 - 1.5 m NW from the
>     known point.
>  2. Points are collected and then mapped in QGIS as NAD83, UTM Zone 10 N.
>  3. The known points include property survey pins, Government control
>     survey monuments, Total Station survey points derived from the
>     above, other GPS results (Trimble ProXRS) and identifiable points
>     on orthophotos.
>  4. I'm using SBAS correction in the GeoXT.
>
> It appears to be adding a consistent offset to the GPS result although 
> no offset has been set in TerraSync.
>
> Many thanks for any thoughts on this situation . . . . .
>
> -----
> Cheers, Springfield Harrison
>
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