Kirk is spot on. That unit is for GIS use and cannot receive RTK GNSS corrections. You will need a survey grade receiver, with RTK corrections (or post processed) for better accuracy.
Budget option for cm accuracy is the Emlid Reach RS or RS2 On Sat, 6 Mar 2021 at 23:53, Greg Troxel <[email protected]> wrote: > > Springfield Harrison <[email protected]> writes: > > > 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 . . . . . > > I'm really not clear on what this particular receiver is purporting to > do, but a consistent meter-ish offset smells like an incorrect datum. > > If you are using SBAS and in the US, that means WAAS. So you are > getting results that in some CRS that the list hasn't figured out what > it is, but "ITRF2008 current epoch" is my best guess. That's > essentially equal to "WGS84(G1762) current epoch". > > Those frames are definitely not equal to any flavor of NAD83. > > qgis, via proj, will treat "WGS84" and "NAD83" both as datum ensembles > and because each ensemble has a low-accuracy member treat them as equal, > and thus choose a null transform. IMHO this is the wrong thing to do, > as WGS84(G1762) and NAD83(2011) are both datums with high intrinsic > accuracy and are definitely not equivalent. > > Converting from ITRF2014 to NAD83(2011) will apply a datum shift. > > Advice 1 is to shift your project CRS from NAD83 to ITRF2014 and see if > the relative position of the observations and controls changes. If so, > you have datum transform trouble. > > My real advice 2 is to take the data file from the unit and label it as > ITRF2014, and then see how things line up. If you are talking about a > meter you need to really pay very close attention not only to datum > labeling but also in understanding the transformations your software is > making. > > Greg > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >
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