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GPS about 30m off

Edwin
3 months ago

I have noticed this twice now. After using my GPSmap 67i for a few hours the gps is at once way off.

We went for a little walk this evening to find a cache. The gps worked fine until the last waypoint. We were on the right spot and according to the gps we were 30m away from that waypoint.

In the hurry of that moment I didn't notice the fault right away, but being home in my backyard I see the gps is still way off.

Multi-GNSS is selected and Multi-Band is on. According to the Satellite page  there could be a variation of 1.8m. On the map I can see the gps is at least 30m off.

Switching the device off and on solves it directly. I had the same experience yesterday (not caching or walking at that time, just playing with this new toy at home), so it is not just a one time glitch.

I wonder if someone else has this experience as well and I hope someone can tell me I can solve this behavior by myself.

Regards,

   Edwin.

  • 0 2 months ago in reply to Edwin

    I'm interested in your experience.  Please keep this thread updated. I have not had that problem with my 67i.  The fact that yours was not showing the correct position of the cache is more interesting than its being off the trail.  Here in the United States trails are often moved for land management reasons more frequently than maps are updated.

  • 0 2 months ago

    Garmin Support contacted me about this (Great!). I uploaded the requested information. I'll keep you posted.

  • 0 2 months ago

    In case this helps, Edwin, I checked the accuracy of my 67i in expedition mode from my kitchen window with the sky mostly obscured.

    GPS Position Precision on 67i

  • 0 2 months ago in reply to Edwin

    I try to experiment my GPSMAP67 outside on a table.

    Clear sky with no trees.

    1) recording control on

    2) GNSS on Horizontal accuracy 2 meters

    3) Altimètre setup a) Autocalibration continus b) Barometer mode (variable elevation) c) pressure trending save when power on

    4) Calibrate Altimeter Current elevation set to 18 meters

    GPS Altimeter and Altimeter reading 18 meters

    After 2 hours GPS Reading was 250 meters and Altimeter reading 18 meters.Theorical accuracy is 2.5mx2.5m= +/- 6.25 meters

    When I switch OFF/ON and after one minute reading is GPS 21 meters and Altimeter 18 meters

    It seems in my GPS there is  a summation of errors in elevation which need a refresh perhaps calibration continuous??It is very strange.

    5) It would be a good thing if elevation was DME reading parallel to GPS reading (I contact Garmin for this)

    6) My horizontal position is OK in this experiment.

  • 0 2 months ago in reply to jlg2

    I updated the test data at the above link.  It now includes a test with a mostly clear view of the sky.

  • 0 29 days ago

    I'm having the same problem. For testing I placed the device on a table, and after about 1 to 2 hours, the position was more than 100 meters away from my actual location. Position accuracy in the satellite page was at 1.8 to 2.0m. After a restart, the position was correct again immediately.

    I also have Multi-GNSS and Multi-Band on.

  • 0 29 days ago in reply to Chris

    That's interesting, Chris.  Did you have recording turned on to see how the drift progressed?

  • 0 29 days ago in reply to Chris

    Sad to hear.

    I was glad Garmin support asked me to upload information so they could investigate. Haven't heard from them since.

    I'm using my good old GPSMAP60CSX for reliability. For now it seems I have wasted some 600euro.

    I'm still hoping I get a working device for my money, but as time goes by I'm not sure this will happen. Advising against this flagship-model for now.

  • 0 28 days ago in reply to jlg2

    Yes, I have. Here's the GPX-file: LINK

    This track was with Multi-GNSS and Multi Band on. The GPSmap was not moved during that about 2 hours.

    After that I started walking around and after just a few hundred meteres the position was back at the real position with a very good precision.

  • 0 28 days ago in reply to Chris

    That's interesting, Chris. 

    I'm used to seeing an occasional outlier in my GPSMAP receivers.  Those outliers might be 100 m or more.  But those are clearly outliers, much different than reports adjacent in time.

    Your track is different.  Your track lasted about 2 hours 14 minutes.  Until the last 20 minutes, all your points were within 10 to 15 meters of the mean position.  It's only in the last 20 minutes that the track starts to drift northward to about 115 m away from the mean position.  None of those points drifting north is significantly different from its contemporaneous points.