[Qgis-user] Trimble GeoXT 2005 Accuracy

Sun Mar 7 03:54:47 PST 2021

Hi Springer.I assume your raw data files are being converted to gpx on  a computer since the raw terrasync files are proprietary binary files. If you are using trimble pathfinder, you can post process differentialy correct the data if you have access to  base station logged at the same time you captured your field data.  Having a base station 100 miles away will not improve your results as the baseline is too long.I do not know if you can write a gpx file directly from pathfinder but I would not bother. I would write a shapefile which will contain the coordinate system you specify.  Simply open in qgis and you should be good to go. If your older unit works better, I would expect it may be an issue with the setup within pathfinder or perhaps the software version.I think your consistent offset is a direct result of how you are converting your data from trimble to gpx.As I mentioned in my previous comments, there are many issues which affect accuracy.  Just because the box says it is accurate  you will rarely replicate that in the field.  In terms of WAAS dataframes, these are processed internally on your field unit.Kirk Schmidt Sent from my Galaxy
-------- Original message --------From: Springfield Harrison <stellargps at gmail.com> Date: 2021-03-07  5:57 a.m.  (GMT-04:00) To: kirk <kirk at nortekresources.com>, Jorge Gustavo Rocha <jgr at geomaster.pt>, qgis-user at lists.osgeo.org, Greg Troxel <gdt at lexort.com>, Dan <19dmb83 at gmail.com>, Nicolas Cadieux <njacadieux.gitlab at gmail.com> Subject: Re: [Qgis-user] Trimble GeoXT 2005 Accuracy 
    Hello All,

      Thanks for the comments, I'll reply more fully tomorrow.

      The receiver is Trimble mapping grade:

      "The GeoExplorer 2005 series consists of:
      • The GeoXH™ handheld, providing subfoot (30 cm) accuracy, or even
      8-inch (20 cm) accuracy
      with the optional Zephyr™ antenna.
      • The GeoXT™ handheld offering submeter accuracy for GIS data
      collection and data
      maintenance.
      • The GeoXM™ handheld with 1–3 meter GPS accuracy for mobile GIS
      applications."

      "Post processed carrier accuracy: 1-30cm".  This receiver was
      probably $5-8000 (?) new.

      Data collection was stationary, open sky, good satellite
        coverage, several minutes of 5 sec observations, good PDOP
      SBAS and/or post processed

    The concern is not the accuracy as such, but the systematic NW
      shift.  This has been observed over several months, consistently. 
      My old Trimble ProXR (1994?, $20K new!) is actually better in this
      regard than the GeoXT!

      The Trimble manuals make no mention of the SBAS CRS, implying
      "turn it on and go, the receiver will integrate the SBAS into the
      rover file."  

      More tomorrow, thanks . . . . .

    -----
Cheers, Spring

    On 06/Mar/2021 15:56, kirk wrote:

      A few notes.

      sbas which is waas in north America is based on
        equatorial satellites which will get you in the 1 m range in
        southern Canada. 

      you can achieve sub decimeter accuracy
        consistently using rtk ,either through a ntrip  caster (base
        station) broadcasting over the intenet or with your own base
        station and a radio link. there are a few chip sets and break
        out boards that you acquire and assemble your own system. This
        is a very inexpensive option.

      Another option in Canada is to use precise point
        positioning (PPP) which requires 6 to 12 hours of observation
        data using L1, L2 or L1 and L2 data and rinex log files. This
        comes in handy if you need to establish a remote base station.

      A proper antennae with a metal ground plane is
        also critical to getting quality results.

      Observing under a forested canopy is difficult
        especially in summer under leaf on conditions,  after a rain
        which creates multiparth mayhem.

      There is a reason survey grade equipment is
        relatively expensive. If you require repeatably accurate results
        in a variety of conditions this is an option.

      Kirk Schmidt 

        Sent from my
          Galaxy

        -------- Original message --------
        From: Jorge Gustavo Rocha <jgr at geomaster.pt> 
        Date: 2021-03-06 6:41 p.m. (GMT-04:00) 
        To: qgis-user at lists.osgeo.org 
        Subject: Re: [Qgis-user] Trimble GeoXT 2005 Accuracy 

      Hi,
      I just jump in this thread to say I'm really impressed with
        Ardusimple. I have a RTK Handheld Surveyor Kit [1] for +- 400 €
        and it works really well.
      I use the national NTRIP service and I have consistently
        precisions around 10 cm with just one receiver. 

      I use a free Android application called SW Maps [2]. My survey
        points, tracks and photos are collect in a geopackage that I can
        read in QGIS. I use it mostly to collect ground control points
        for my drone flights.

      Regards,
      Jorge Gustavo

      [1] https://www.ardusimple.com/product/rtk-handheld-surveyor-kit/
      [2] https://play.google.com/store/apps/details?id=np.com.softwel.swmaps
      Às 20:12 de 06/03/21, Greg Troxel
        escreveu:

        Springfield Harrison <stellargps at gmail.com> writes:

          Thanks Dan.  See my relies to Kirk and Greg.  The Emlid sounds
interesting, will have a look.

        I have an earlier Emlid Reach (not RS or RS2), which has L1 only, and I
never got it to work well.

Also look at the Ardusimple unit -- but it's more a parts kit than a
system.  You need a way to get RTK reference data in, and a good
antenna.  One approach is Vespucci (OSM editor for Android) as a
datalogger, and the Ardusimple WiFi NTRIP master to get corrections over
the phone's hotspot.

  https://www.ardusimple.com/product/simplertk2b/

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