Tactix7 Pro vs Garmin Edge 1030+ tracking distance variations

Yesterday I cycled over the Burma Road route in Aviemore. Great.

I have a Garmin Tactix 7 on my wrist and a Garmin Edge 1030+ on my bike. I'm on latest full firmware release versions on each device - no betas.

My Tactix recorded 79km and my 1030+ recorded 62km - quite a difference. As the crow flies I was expecting the route is about 62km. My wife's Apple Watch recorded 62km on outdoor cycling

Why such a big difference? Altitudes were the same - max elevations were the same at the same map point.

Tactix 7 was set to on eMountain bike and Edge 1030+ on ebiking (not mountain bike)

Which was the right distance?

I’ve tried a site to compare to gpx tracks and both tracks looks almost identical.

Going to Garmin Connect - If I look at position on the map in the activity and compare map position at 15k and 20k on both tracks - 1030+ and T7 are same position on route pre hill at 15k. At 20k (5km into a steep climb) the 1030+ is about 2km further on than T7. It looks like T7 is taking the 14% climb and adding vertical distance to the track as well as horizontal distance.

From bottom of the climb (240m elevation) where both devices record 15km track distance at the same map location to the top of the climb at (688m elevation) - 1030+ is at 20km and Tactix is at 30km. Times into the ride by position on hill are identical over the same period.

Bug in one of the devices or is elevation being taken into account to calculate ground distance travelled in the watch. Could this be the effect.

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0 Dr Phil over 3 years ago

Is one of your devices getting speed/distance from a wheel sensor and one from GPS?

0 gaijin over 3 years ago

Do you have 3-D Distance enabled on the T7?

0 peterwwood over 3 years ago in reply to Dr Phil

My Tactix7 is getting cadence & strokes from the bike - both average and max cadence. It doesn't appear to be getting anything else.

2 days ago I did another flat run and the Tactix7 showed less km total than the Edge.

What do you think is going on?

0 peterwwood over 3 years ago in reply to gaijin

No - its off

0 peterwwood over 3 years ago in reply to Dr Phil

Philip - I have had a look in sensors and there is a speed/cadence sensor picked up by the eMTB - I have checked and the wheel size on the sensor is set to 2335mm and 'auto'.

there were 9264 strokes also recorded by the sensor.

0 peterwwood over 3 years ago in reply to Dr Phil

just checked tyre size and is a 622-66 - so I reckon circumference is 2370mm - its a mountain bike.

0 ekutter-dnu over 3 years ago

As Philip says, this is probably caused by something with the speed sensor. Not sure why the calibration would have suddenly changed, but if the tracks are basically identical, that's the only thing that could explain this kind of discrepancy. Unless you're going up 30 degree hills, the elevation wouldn't be able to explain it. Even at 6%, the difference in distance of 2d vs 3d is pretty negligible.

If it were me, I'd disable the speed sensor on the devices. GPS tends to be so good these days that even on winding MTB trails, I find GPS distance every bit as reliable as a speed sensor. When I have used a speed sensor, I always go inconsistent results with auto calibration. So if you are going to use the wheel sensor, at least do a manual calibration, and set it to that.

0 peterwwood over 3 years ago in reply to ekutter-dnu

thanks - I will remove the speed sensor and try it again.

0 peterwwood over 3 years ago

I have checked my sensors once home. I have a speed / cadence sensor on my list in the watch but it refers to a Spd/ cad sensor made by Garmin and connected on a KeiserM3 indoor spin bike. Not a sensor on my mountain bike.

SO this is even more of a puzzle to me - back to - watch with no 3D settings and no Spd/cad sensor attached and not connected to my eMTB shows 79km ride and Garmin Edge 1030+ and a Garmin Montana 700i and an Apple Watch 7 all show 62km.

Still would like to know what the reason is.

Wonder if any of the Garmin Support guys on here can shed a light.

0 ekutter-dnu over 3 years ago in reply to peterwwood

If you post the activity.fit files (from the activities folder) for both devices I'd be happy to take a look. I have a tool that lets me look at the low level mesages that would also show where it's getting speed and distance from for each data point and what sensors are actually connected. All that info is actually stored in the activity.fit files. You'd need to put them in a .zip file to post here.