shown speed is wrong

my 840 is non-solar with fw 21.18

I use the automatic GPS mode, which mostly defaults to the 'basic' GPS and the accuracy always has been spot on.

Today I noticed, that sometimes (especially in the forest or at a 'tree avenue') when there is no clear sky above, the shown speed is wrong. e.g. I was quite constant at around 32kph and the 840 shows 22-26kph.
I checked the sections in the fit-file, showing that I was in fact around 32.

This probably has something to do with the rapidly dropping reception. Has somebody else experienced similar?
I will check if this occurs with the more precise modes too

0 1530214 4 months ago

Yes this happens to me in wooded areas, my speed will drop by at least 10kph compared to my actual speed and then finally catch-up. On my other bike I have the Garmin speed sensor and this eliminates the issue.

0 looigi 4 months ago

That's one reason Edge units are capable of working with a wheel speed sensor even though they have GPS. At the slower speeds and sometimes tortuous tracks and conditions that bikes sometimes ride in, a speed sensor can improve things. I have speed sensors on all my bikes. The Garmin sensor works great, but there are others as well.

0 franz134 4 months ago

I know that a speed sensor will help, but what confuses me is the fact that the fit-file displays correct data - just der data field during the ride shows wrong values