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Edge 1040 GPS Distance vs Speed Sensor Distance for Mountain Biking

Former Member
Former Member over 2 years ago

I finally got around to testing this.  My brother and I both used Edge 1040. 

I used the original Garmin Speed sensor on my front wheel.  Granted - I haven't calibrated it in several years, but I recall doing so in a large paved lot.  My brother did not use a speed sensor, but rather, used the stock settings for the Mountain Biking profile (I assume this has the higher gps settings by default).  Both running firmware 14.5

We rode almost entirely through heavily wooded singletrack in valleys, with many 300' descents and climbs.  Most of the trails were on ravines with tight switchbacks. 

With speed sensor, I logged 21.75 miles

Without speed sensor, he logged 20 miles

I think this is actually pretty good compared to the older models, given the terrain.  Although I don't see the sensors as a necessity for road and gravel (unless you go through a lot of extended tunnels) - I will continue to use them for singletrack mountain biking. 

  • 0 over 2 years ago

    Calibrate your speed sensor and try again and report back.   

  • 0 over 2 years ago in reply to Pat Fulghum

    Default is auto calibration, which should give the best results.

  • 0 over 2 years ago in reply to lvanjaarsveld

    Auto-calibration works best on a relatively straight segment and less well over a tortuous track. On my previous Edge units I could trigger an auto calibration by switching to manual then back to auto.  I'd do this a couple of times over a straight segment, record the cal numbers it came up with, then switch to manual and enter that number so it would use that from then on until I chose to change it.

  • 0 over 2 years ago

    Nearly 10% difference is substantial. I would take a close look at the GPS track and see if it appers to be accurate or is cutting corners due to lack of GPS signal. If it's a poor GPS signal, however, the track could wobble away from the actual route resulting in an apparent increase in distance (although this depends on how intelligently the device handles the poor signal problem). I have my Edge set to 1 second logging interval to help with closely checking a track.

  • 0 over 2 years ago

    10% has been about the same average I’ve seen over the years with and without sensors in single track, it can really add up to a lot of missing miles over time

  • 0 over 2 years ago in reply to JRat1

    10% is actually not bad for GPS distance, where 20% is normal with GPS only in my experience.  I did an all day multi-park MTB challenge a month ago using my 1040 and of course my speed sensor battery died early on, and with multi-band I logged 63 miles where 2 others that I rode with logged 68 and 70 miles with speed sensors.  This was all singletrack with a lot of tight and twisty trails under dense tree cover.

    I still use a wheel sensor on my MTB even with the better GPS in the 1040.  From what I've seen multi-band doesn't drift as bad as normal GPS, but it is still limited by the 1 second sample rate so it will potentially cut corners or straighten out winding sections of trail.  It doesn't do well with rolling terrain either, so going through a series of dips on otherwise flat ground my not account for the vertical distances through the dips.  Especially if the recording points all end up on the flat level of the ground.

  • 0 over 2 years ago in reply to Sven1294

    With a wheel sensor, it counts wheel revolutions, so the sampling rate is immaterial to as far as distance accuracy is concerned.

  • 0 over 2 years ago in reply to looigi

    Which is why I use a speed sensor on my MTB...

    Since the discussion is GPS vs speed sensor I figured I'd share my relevant experience.

  • 0 over 2 years ago in reply to lvanjaarsveld

    Auto calibration uses gps to estimate wheel circumference. 

    The most accurate would be to measure the wheel circumference and manually enter it.