SoSmellyAir

Does anyone know why there is such a huge discrepancy in elevation gain between the Yahoo and Strava iOS apps? (Please note I am just asking about these apps, not about an altitude difference between GPS and barometer.)

I use the Wahoo app to record my rides, then export the data to the Strava app afterwards. For my most recent ride, Wahoo shows an elevation gain of 2,555 ft. while Strava shows only 1,616 ft., but the two apps agree about the ride distance (to within 0.01 mile). Which elevation gain number is more accurate?

tomato coupe

Did you finish the ride where you started? If so, did the Wahoo give you the same number for ascending as descending?

SoSmellyAir

Yes, on my driveway right outside my garage.

No. According to the Wahoo app I finished my last ride mid-air 82 ft. above where I started.

WhyFi

One of the apps is likely referencing their own elevation model. Strava certainly has this option available, as evidenced by their elevation 'correction' option on the desktop site.

shelbyfv

I let Strava "correct" the elevation. It's always a couple of hundred feet more than Wahoo.

phrantic09

Buddy of mine has an Wahoo computer (not sure which) and he almost always shows 10-20 feet of elevation gain, even in courses with 5000. Not sure what the cause is.

Iride01 

Because they don't figure up the data the same way. And they might not use the same data sources.

Remember that thing about a man with two watches?

SoSmellyAir

But "I use the Wahoo app to record my rides, then export the data to the Strava app afterwards." So the data source should be the same, i.e., the GPS data from my iPhone.

Iride01 

They may not use your elevation data exactly as it's recorded in your device log. There is probably a lot of massaging of the data to eliminate what each site might consider errors or noise.

Just pick a site and use the data you think is more accurate. Over the course of many rides, it might average out to being close with either site. To take one ride and compare it on multiple sites is just as crazy to me as assuming your device is even correct about the elevation gain and loss you had.

Accuracy really isn't as important as just knowing one route is more climbing than another. And you can figure out that by adding and averaging out the rides of the same route. Throw away what looks like outlier data for any one ride.

spelger

the data source *is* the same. the difference is that Strava post processes it and might make corrections. GPS elevation data is not as good as barometric elevation data. Strava knows the difference and adds correction as needed.

Seattle Forrest

Both of the apps you use do their own magic on the data your iphone GPS gives them.

fishboat

I don't use any of the recording devices nor software mentioned to workup my ride-routes/tracks, however I have stayed at Holiday Inn Express & did a fair amount of mapping and map-data manipulation in a former life. When you talk about "ride data" and recording ride data and having various sources workup that ride data you need to really understand what all that means. It may well be that the ride data, in terms of the track that was followed, is simply the gps track itself. "Tracks" and "Routes" are nothing more than a large collection of latitude/longitude pairs. Even if you're transferring ride data that contains elevation, or other associated data, the destination software may only use the lat-lon data(plus time meta data) and then use their own data(sources) to work up other metrics as needed. While the lat/lon points(+time) are unique and transferrable, the remaining output can & will vary depending on data sources, assumptions made, and software(algorithm) processing. Mapping data sources are somewhat a commodity and they do vary.

As mentioned above.."The man with two watches doesn't know what time it is".

Seattle Forrest

A man with two watches needs to know how to spell.



Maybe somebody at Wahoo or Garmin missed that left turn in ABQ?

SoSmellyAir

Thank you for the detailed explanation.

The man with two watches knows it is time to shop for a third watch.

tyrion

"Always choose the device that indicates the greatest elevation gain."

need to add that to The Rules.

https://www.velominati.com/comment-page-8/

fishboat

Nope. The only thing a third watch will do for you is give you a better estimate of what the time actually is (when the time from all three is averaged).

SoSmellyAir

Much as I see the appeal in your proposed rule, I must go with the Strava app in case anyone else on Strava or the Southern California sub-forum invites me to a real 2,000 ft. climb

SoSmellyAir

Au contraire mon frere, perhaps you misunderstand ...

A single watch is for telling time.

A second watch may give you a better estimate of time to the extent it is more accurate than the first and you have both watches side-by-side.

A third watch, even if it provides an extra data point, does not instantaneously -- and this is the crux -- give you a better estimate of time, because it takes longer to average three data points than two.

Thus, the third and any additional watches are not for improving one's estimate of time, but to collect for admiration, decoration, projecting wealth, signaling taste and/or restraint, and god forbid (for us cyclists), fall detection (Apple Watch).

It is largely analogous to the N+1 rule I often hear about on BF.

MoAlpha

I thought Strava elevation correction was based on the map datum and threw out the altimeter readings, which are always crap.

WhyFi

With a dedicated bike computer, Strava will take whatever elevation data it is given. It will only correct with their own data if you select that option for a given ride. I don't know how it works for the phone app.

MoAlpha

Right. That's the correction I as referring to.

Seattle Forrest

Strava throws out the recorded elevation data unless you used a barometer.

SoSmellyAir

Got it. [sad realization]

Seattle Forrest

If you didn't use a barometer, the elevation data you recorded is likely to be wrong enough that Strava's corrections will actually be helpful.

SoSmellyAir

Thanks, I now realize that. There is a new route I want to explore which starts with a long climb (partly on a major road) so a more accurate estimate of my elevation gain would be helpful.