- Strava – altitude gain issues…..v Garmin
Just completed a short but lumpy ride on the Dairi pak challenge this weekend. Only 22 miles but the published route advised 5220 ft of altitude gain, which for me anyway was fairly stiff in such.a short distance.
Long story short, Strava came up with 3220 ft of altitude gain.
Conclusions, I am much less “nails” than I thought I was (which was not very “nails” at all) or one or other piece of kit (Garmin or I-phone/Strava) is rubbish. 2000 ft out is a poor margin of error
Thoughts please…..Posted 6 years agocrazy-legsSubscriber
I’d say the published info is out.
3220ft is pretty hilly but much more realistic than 5220ft in 22 miles.
Rough rule of thumb I use is 1000ft altitude gain per 10 miles which generally works well unless you’re specifically seeking out every hill or you live in East Anglia.Posted 6 years agocrashtestmonkeyMember
FB conversation after Ronde Van Calderdale (about 3000m of climbing so big enough to highlight differences) was that Garmins seemed to give higher (but consistent with each other) elevation gains than other devices, be they other brands of dedicated GPS, or smart phones running apps.Posted 6 years agoAlexSubscriber
Phone’s generally over-estimate especially in hilly areas where sometimes the overlay gets confused if you’re on a ridge or climbing it. I ran Strava on my phone and my Garmin 800 simultaneously for a while and the phone was always 10%-15% over. Although the Garmin wasn’t perfect either (recorded about 3% diff over the same route).
With auto pause on, my GPS seems to be about 10% less k’s as well as my phone. It does auto pause on very steep climbs tho which is a bit depressing when you’re blowing it up out of you ar£s as Andy W says.
I once had all this properly explained by Andy @ Tracklogs but forgot most of it!
3500 feet of climbing in 22 miles? That’s not hilly 😉Posted 6 years agoroneSubscriber
Friend and I were discussing this yesterday. Both 800s we had were different… They’re obviously affected by pressure so as I understand it the weather can alter the readings. I assumed that mapped data should be more accurate as it’s correctly surveyed data. But this too depends on how your device is tracking the land and its subsequent conversion in strava.Posted 6 years agogofasterstripesSubscriber
GPS is not as good at determining height* as it is at determining position around the Earth’s surface. I don’t know if the Garmin in question ONLY uses it’s altimeter, but this may a factor. Having said that, that there is a fairly hefty difference in those figures which this may not entirely explain!
*GPS uses triangulation, and while the sats are spaced out well, the “Height” of the triangle they are mapping changes by VERY small margins when you climb a hill or two.Posted 6 years agoandytherocketeerSubscriber
There’s a really old thread about this somewhere. I put an identical Garmin file in to (iirc) Strava, Everytrail and Endomondo to see what they do. In short, (iirc)
– Everytrail just added up all the small + an – gains/losses in elevation (so the total height of a flat road is not zero, due to GPS/Alt errors).
– Endomondo did some kind of smoothing (so it makes you total climb/descent look less than what might be published)
– Strava conjured up extra height gain/loss that was not even in the file (no clue why or how), but I think in general it does much the same as Everytrail with little smoothing. Nuked my Strava a/c so I can’t easily double check this.
I’d normally ignore published altitude gain for a trip, because you have no idea how it was recorded. iPhone? GPS+Barometric? Smoothed out data? All the main dips/valleys and summit altitudes read directly from an OS map?
It also goes a bit asymmetric if you have lots of data points going uphill (slowly), and fewer going downhill (faster), especially with lots of switchbacks, unless you’re lucky and teh GPS records a datapoint right at each apex.Posted 6 years agoMarkBrewerMember
I did a 24 mile ride on the Quantocks last weekend. At the end of the ride my phone had recorded over 5000 feet of climbing but when I saved the ride and uploaded it to strava it changed down to 3500 feet which seems more likely.
I just assumed that it corrects the phones data to the actual elevation when you upload it? Seems to do it with the mileage too. I’ve only just started using strava as sports tracker pro seems to take ages to pick up a GPS signal these days.Posted 6 years ago
Seems that Strava underestimates. Which I’d rather have in all honesty. I hav no wish at all to book onto a challenge that a GPS system says has an amount of climbing I can do, and then die a nasty death up some ridiculously lumpy course.
I’d rather be pleasantly surprised.Posted 6 years ago
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