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 <[email protected]>
Date: 2021-03-06 4:35 a.m. (GMT-04:00)
To: qgis-user <[email protected]>
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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