After a Half-Iron distance race at the weekend, today was still a recovery day. 10k on a bike seemed sensible enough as did the thought of combining that into a GPS test. The cunning plan was to circle the Roundabout-of-GPS-Doom.

Perhaps a faster-moving me might give rise to different GPS results than previous running-based tests?

The Teams:

1. Team Garmin
   1. Forerunner 920XT
   2. Edge 820
2. Team Suunto
   1. SPARTAN Sport
   2. SPARTAN Ultra

Match Conditions

1. All latest firmware as of 27Sep2016.
2. Wrist-worn except 820 (this might favour the 820 very slightly)
3. Cloudy, daylight, light wind, 17 celcius. No tree cover, no buildings.
4. 15 minutes of GPS recording in a warmup ride.

Here is a clickable image of the main talking point of the match.

Results

• Distance – all were in the range 9.69-9.74 and I stopped the watches whilst moving which could easily account for 20m. They’re basically the same.
• Power – the two Garmins tracked the average as 200w from the same source +/- 1.2w from a ROTOR 3D+ InPower single sided crank.
• Speed – was near-identical, although the 820 had a minor wobbly at 7:30 minutes. A yellow card offence.
• Elevation – The 820 failed at elevation (referee wasn’t looking, otherwise a second yellow) – A surprise as in training at the weekend over 90km, the 820 and 920 both performed near identically. For the other Garmin and 2 Suuntos, I could not tell which was correct.
• HR – both Suunto’s simultaneously lost the HR track from the 4iiii Viiiiva. that is almost certainly BTLE a transmission issue from the dual-band 4iiii HRM. However the ULTRA didn’t pick up the HR again when it came back on track. That is a yellow card offence.
• GPS Tracking (Visible judging of the above map) – all 4 tracked the ‘pattern’. The two Garmins were off the track a few metres skewed to the East. SPARTAN Sport was ‘just’ the most accurate looking.

Result

In the GPS game there are no points won or lost for power/speed/elevation performances. So all that mattered was the GPS track in what, I have to say, were UNchallenging and near-perfect conditions. The first image shown above was indicative of the performance of the entire route. They were all very good boys and girls and performed well. At any and all points they were probably no more than 5m out from each other. THAT is supposedly the accuracy of a GPS signal or thereabouts AFAIK.

A DRAW, in normal time.

For the penalty shootout I would say that the Team Suunto just edged it (pun intended) but only because of the Garmin’s Easterly skew. HOWEVER, based on this test, I would have no problems buying any of them on GPS accuracy grounds. Other recent test with these devices are <here>, <here> and <here>. My tests are not scientific (look at fellrnr.com when he gets a SPARTAN)

Edge 820 – The speed issuette and the elevation track were a little concerning. Personally  I’m interested in neither bike speed nor, usually, elevation. But some of you are. Genuinely, over the 90km at the weekend both Garmins tracked elevation consistently – although the Edge was consistently lower. That could quite easily be put down to me never bothering to calibrate it.