Hokiedad4

My Wahoo Elemnt has performed brilliantly but I have minor accuracy issues with respect to distance and elevation. My rides consistently show more mileage than other riders or the route. Not by much, maybe 1-2%. And the results show more climbing than descending. For example, a short ride this past week showed +679/-608 ft, although I start and finish at the same location.

I am using speed, cadence and heart rate sensors. The device is configured with the default circumference for my wheels (700x25), and I've also manually verified it's correct.

Appreciate any ideas.

DrIsotope

Ascent is measured with a barometric altimeter, which while it's the best way to do it, is still subject to the whims of the weather. My Elemnt Bolt is the most consistent unit I've used yet-- yesterday's ride was off by just 4 feet, relative to Strava's calculation. My Edge 520 was low by ~10% on its best days, and had done as poorly as -30% several times. I literally mean I would ride a route I've covered dozens of times, with a known amount of ascent/descent-- say 1,000ft, and the Garmin would say 675ft or 715ft. I can think of maybe half a dozen rides in 3 years where the Garmin was even close. I just became conditioned to hit "correct elevation" on every ride that went onto Strava.

I get the differing descent/ascent numbers all the time, and believe it has everything to do with where the bike is parked before the ride, and then where the ride takes place. It's not uncommon for my bike to experience +/-25ºF when it rolls out of the shop (which also magically seems to stay at 50%RH almost all the time,) so the barometric altimeter gets a shock right at the start. Even at that, elevation correction is usually unnecessary with my Bolt. Most rides are within 20ft of Strava's calculation, and I'm not quibbling over a few hundred feet a year. My Garmin once shorted me (relative to Strava's corrections) 7,000ft in one month.

Iride01 

You can't compare what you did on a ride with another persons device with the expectation that they will be the same. There will be so many variables that will take pages of discussion to get to the bottom of understanding. Even two riders with the same device will have differences for any two rides compared.

Your device is not a survey grade instrument. Any one particular ride will have many inaccuracies besides altitude.

Remember that the barometric pressure around you is not a constant. Sometimes its a slow change but other days it may be a fast change. A one inch change in barometric pressure is equivalent to 1000 feet of elevation. So on days that pressure is rising, you can expect that you will wind up with more loss than gain and vise versa for falling pressure.

Don't be a bean counter just because something doesn't seem to balance. The data is valuable over time as you compare trends of the same or similar rides.

pdlamb

The best information I've found is that the Elemnt uses satellite (GPS) to calculate elevation, while the Elemnt Bolt uses the pressure-based altimeter DrIsotope mentions. It's a pick your poison kind of thing. Pressure based altimeters are susceptible to fronts moving through. Calculating climbing from a map or direct GPS has its problems, too. If you get it from a map, you've got the potential to lose a lot of climb cred if you only count contours (how many times can you climb and descend 75' and not get credit because you're between 100' contour lines?), or you can get ludicrous over-estimates from a simple map interpolation routine. GPS elevation is a long way behind GPS latitude and longitude accuracy, and if you're in narrow valleys or under trees it gets worse.

My older Garmin 800's pressure-based altimeter has been quite accurate on climbs where the road has lots of elevation markers.

DrIsotope

The Elemnt (non-Bolt) definitely has a barometric altimeter, Wahoo seems to use some sort of algorithm (as they all do) where the GPS and speed sensor (if present) are also used to fine-tune the ascent/descent measurement. Or so says the tech docs from Wahoo. My wife's near-vintage Edgo 500 had an astonishingly consistent altimeter, often recording the same ascent on repeats over the same course down to the foot.

TimothyH

+1

These are order of magnitude tools. Absolute accuracy should not be expected.

1 to 2 percent difference is acceptable.

Most of the guys I ride with have ceased caring about minor differences between riders.


-Tim-