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FR945 Elevation issues

andretol
over 3 years ago

Hi,

I've been using the FR945 for running the past year, and have had issues with the elevation being off the chart.

Typically, it gives 50-100 % as much elevation gain as those I run with, and the same compared to elevation gain if I choose to use adjust the elevation based on Strava Elevation Data. I have calibrated the altimeter using manual elevation to 232 meters, as I know the exact elevation of the front of my house from the local digital terrain model. Settings are:

Auto cal.: On

Sensor Mode: Altimeter Only

Elevation: Meters

Today I wanted to see how it is actually behaving, so I ran with my FR945, my old FR235, and my iPhone 13 mini, and then compared this with the high-resolution digital elevation model from Norwegian Mapping Authorities.

Here you can see the result plotted, and how the FR945 starts out fine, but then shoots up to over 300 meters, where the DTM rounds off at around 280 meters. It continues to have wrong readings for some time, before dropping a lot under. Halfway into the run it recovered and followed quite closely.

The final elevation gain from the FR945 was 294 meters, and the DTM/Strava was 203 meters. I have reset, cleaned the sensor holes on the back, updated firmware, etc. 

Anyone have any further suggestions before I bring it back to the store?

Thanks.

  • 0 over 3 years ago

    I am really impressed by your analysis.  It looks like you manually calibrated at the start of the activity.  Did you have any weather to start the day?

  • 0 over 3 years ago in reply to rbf2000

    Thanks. I calibrated at the start of the activity. Still the FR945 measure climbs much higher and faster than both the FR235 and the true DTM model.

    The weather was very stable and sunny, so I don't think the weather could have done this. I forgot to mention that the FR235 had an empty battery after 45 minutes.

  • 0 over 3 years ago

    I recommend that you contact Garmin support. The altimeter on my FR945 became wildly inaccurate and was replaced under warranty.

  • 0 over 3 years ago

    My suggestion is to try disabling the "auto cal".


    Probably if u are in a zone with poor GPS signal it can "overcorrect" the altimeter, resulting in that error

  • 0 over 2 years ago

    For some time I too have had big problems with altimetry, but I never believed in a HW failure, in fact with the new release the altimeter has improved considerably and we are within the error of 10%, it is not yet perfect but at least acceptable