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'Off course' and 'course found' alerts in rapid succession / riding 10m off road

During my last ride my 820 alerted 'off course' and 'course found' in rapid succession. I mean notifications following up every 3 or 4 seconds which was really annoying. I suspect this has something to do with a poor GPS signal. My previous device (Edge 800) also notifies when I am off course but has a longer delay (I think about 15 seconds or so) in which case the alerts do not show up in rapid succession. I would like to have an option to setup the delay time for my 820. Is this a possibility or can this be changed in the next firmware?

I have also noticed I seem to be riding 10m (not always by the way) offroad while the GPS signal was good. Is there a flaw in the map of is my position calculated wrong (which also would require a firmware update)?

0 Former Member over 8 years ago

I experienced something similar with a Strava Segment a few weeks ago, I turned off the track during a segment and got the 'off course' and 'course found' in messages rapid succession.
I rode further away from the segment and the messages stopped.

0 dpawlyk over 8 years ago

You'll get the "off course warning" if you lose GPS signal (like going through a tunnel).

If you lose GPS signal, it's possible that the unit will have the warning in "a rapid succession" if the signal reception is right on the edge of working/non-working.

I've seen weird GPS reception issues but they are rare.

The other reason you can get the "off course warning" is when the location of the track (based on the map used to plan the route) doesn't quite match the road you are riding on. You should be able to see this on the screen: your light blue line won't be following the purple track line. Your "10 m off road" issue could indicate that the road isn't in quite the right place on the map.

The "off course warning" is based on your distance from the loaded track (it doesn't require a map at all). If there's a GPS signal, there is a delay on getting the warning (you have to be some distance from the track before the unit issues the warning. It appears the warning is faster with the loss of the GPS signal (it's possible that the apparent distance becomes greater without a GPS signal).

Your position isn't determined using the map.

I'd suggest seeing if this is a regular occurrence before worrying about it.

0 Former Member over 8 years ago

I think in my case the problem was made worse by the fact that I stopped to try and cancel the alert, I must have been right on the border between found and not found and the 820 appeared to be in a loop, as soon as I started moving away the problem sorted itself.

0 dpawlyk over 8 years ago

I think in my case the problem was made worse by the fact that I stopped to try and cancel the alert, I must have been right on the border between found and not found and the 820 appeared to be in a loop, as soon as I started moving away the problem sorted itself.

Your location by GPS varies even if you are not moving.

If the GPS error is +- 3 feet and the "off course" distance is 30 feet, your measured position could have been changing from 27-33 feet (bouncing between on and off course).

0 jaslid over 8 years ago

I've been experiencing this on most rides when navigating.

Tonight, for unrelated reasons, I downloaded GPX files of recent rides from Garmin Connect and imported them into Basecamp...

...and discovered several instances where the Lat/Lon values recorded spiked for 1 second to 0.0°E 0.0°N. These spikes are presumably automatically filtered by Connect and Strava, so I wasn't previously aware of them.

I have yet to sit down and correlate these zero points to when I remember 'of course/course found' toggling, but I obviously expect they will.

I'm concerned why these 1 second duration 0.0°E 0.0°N events are occurring in clear, wide open space :confused:

0 Former Member over 8 years ago

Your location by GPS varies even if you are not moving.

That's exactly what I suspected.

0 RayRay4105 over 8 years ago

550

I'd suggest seeing if this is a regular occurrence before worrying about it.

Actually I do not worry about it, but the constant alerts are very annoying. The 800 'waited' a bit longer (10 to 15 seconds) before it presented the off course warning. By doing this it also dismissed false positives due to gps error by itself. I would like to have the same delay in the 820 (hard coded or even better by a manual setting).