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Elevation gain

Old 08-07-21, 03:10 PM
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Originally Posted by tenrec View Post
I generally keep track of my rides using a cycling app. I have noticed that the reporting of the elevation gain statistic by the apps is wildly variable. For example, here's what the app told me for the last 10 times I did my frequent 18-mile ride:

Elevation gain (in feet):

These are the same ride along the same path on different days. These were tracked with the Samsung Health app in my Android phone, but I've gotten similar inconsistency with other apps (including Strava and Map My Ride) and other phones (including an iPhone.) How do the apps keep track of elevation? Do they use GPS data (which I think would be very accurate) or barometric pressure (probably less accurate)? Has anyone else noticed anything like this?
One thing to check is how close the elevation gain is to the elevation loss for each of those rides. That could give a clue as to what is going on.
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Old 08-07-21, 05:13 PM
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Originally Posted by tenrec View Post
I find that utterly remarkable.
It's basically the same way radar works
Genesis 49:16-17
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Old 08-09-21, 05:47 AM
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Originally Posted by iride01 View Post
atmospheric pressure isn't constant. It's always changing. A change of 1" or hg (mercury) will equal 1000 feet of elevation. So even on a short ride, it's reasonable that the barometer might have changed a few tenths of an inch, so 200, 300, 400 feet of difference will be in the ballpark.

Elevation gain is just a gee-whiz number, don't get caught up in it. If you want to climb good, then climb a lot.
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Old 08-09-21, 08:35 AM
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Originally Posted by tenrec View Post
I just found something else of interest: looking back at my records, I found a couple of rides in 2016 which I tracked using both Strava and the Samsung S Health apps. On the first ride, over a 23-mile course, Strava recorded the elevation gain as 1299 while Samsung pegged it at 1721. On the second ride of 17 miles, Strava recorded a gain of 892 feet, while simultaneously Samsung gave me 1381 feet. The phone I was using at the time was probably a Samsung Galaxy S8. So here are examples of different apps on the same phone at the same time giving wildly different reading of elevation gain.
Doesn't surprise me. GPS is an inherently noisy system, and there's a lot of signal processing software embedded in a good GPS system's chips. I suspect Samsung focuses on location (because that's what most people want, like do I turn left or right to pull into the doughnut shop?) and lets the elevation fall where it may. Strava will try to post-process the intermediate GPS track your phone produces to fit it onto its maps. As long as lots of people have ridden those roads and tracks, Strava will cut the noise in the phone track down. Does that mean Strava is "right?" Well, it means Strava likely has a better estimate of the climb.
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