I've been having some horrible issues with a GSC-10 cadence/distance sensor in conjunction with Edge 500 lately which results in cycling activities being recorded with much, much shorter distances than was actually the case.
When uploading to Garmin Connect the system sadly believes the distance data in the FIT rather than looking at the satellite data. Eg. say I ride 10km down a straight road, using GPS co-ordinates it would be obvious the ride was 10km, but due to sensor data being incorrect the Edge says I've only done 5km or something.
Trouble is, when this happens there is no way to fix the data uploaded to Garmin Connect. It is possible to take the FIT file and load it into a 3rd party site (such as GPSies.com), export as GPX and then re-upload to Garmin Connect. This other site throws away the distance data from the file and re-calculates it based on pure GPS co-ordinates. Sadly though, it looses heart-rate, cadence, temperature, etc. info as these are not supported by GPX.
If only, when one notices distance errors on their activities, one could ask Garmin Connect to re-calculate this based purely on GPS data. I envisage this would be a button just below the current, 'Elevation Corrections' link. In fact, this is so easy to do perhaps the site should always do it and give a warning that your wheel sensor might be incorrect and recommend using corrections.
I'm sure this is easy to do and would really help those who notice 'dodgy' distance data like this.
Thank you :)