[Qgis-user] Trimble GeoXT 2005 Accuracy

[Nicolas Cadieux]

Hi,
I don’t currently have enough internet to check out the unit but I imagine this is a single band unit with an onboard antenna.  I imagine you are using it in “point and shoot mode” or static mode where you are not taking measurements over a long period  time, nor are you using a second unit for correction or doing any kind of post processing.  If this is the case, you are getting a very good reading!

Getting a systematic error in the same area (NW) would indicate you are getting a bad satellite coverage or that perhaps, you have a obstacles.

Make sure you have a clear sky, that the unit has been working for 10 to 20 minutes before the reading, that the satellites are well distributed and that you are picking up up 4 or more (8 or more is better).  Take multiple reading on the same point over a long period (you can average out the positions) make sure you don’t have another unit close by.  Using satellite from other constellation (like the Russian gps) can make thing more problematic some times.  

This is good for static mode where you just point and shoot and get a instant reading.  Anything under 5 m with a 200$ to 1000$ unit is good.  Anything under 1m with a 1500$ to 4000$ unit is good.

Nicolas Cadieux
https://gitlab.com/njacadieux

> Le 6 mars 2021 à 03:35, Springfield Harrison <stellargps at gmail.com> a écrit :
> 
> 
> Hello All,
> 
> I recently acquired a Trimble GeoXT 2005 Series and am puzzled by the results it produces:
> 
> 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.  
> Points are collected and then mapped in QGIS as NAD83, UTM Zone 10 N.  
> 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.  
> 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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