Using the exact same device (iPhone 7+) with both apps open at the same time, I am getting some fairly significant differences in over all mileage and vertical feet climbed. If my GPS signal is coming from the same device at the exact same time on the exact same trails, why would the Strava be about 14% more? Seems strange, but perhaps this is something written into the code of either Strava or Cyclemeter for some unknown reason. Anyone else notice this discrepancy between these two apps? Which one do you feel is more accurate?
Here is what happened:
Stava recorded 23.81 mi, 3981 elevation gain with a moving time of 3:42.08 while averaging 6.4mph and 1803 calories burned.
Cyclemeter recorded 22.37 mi, 3501 feet climbed with a moving time of 4:01.07 while averaging 5.57 mph and 1839 calories burned.
My stats are the same in both apps.
Seems very strange indeed.
You're going to get variance between devices and between apps. Almost nobody out there is using the 100% raw GPS data from the hardware with zero processing. And if they did, you'd see a whole lot of junk. Trust me, that processing is essential to get anything useful out of the hardware. Especially phone hardware. The differences in how the apps process that data are going to account for the differences in what they spit out for positional data.
Elevation, you might as well just stop complaining about right now. The act of measuring elevation is MUCH more challenging. Especially considering HOW that elevation is measured. On your phone, you get one of the least accurate methods available, so consequently, the apps most likely assign an elevation value from an elevation model based on the position determined by the GPS. With different results in positional data, you'll get different elevation results by default.
I've never used Cyclemeter but I know that Strava is very inaccurate. I have a Cateye bike computer that is very accurate and Strava shorts me mileage on every ride. I know that it is because the satellites have a hard time "seeing" my phone through the trees. A twenty mile ride recently Strava shorted me 2.5 miles.
I just chalk that up to the difference between using a mechanical device and GPS system that is limited in it's ability with the very tight turned trails that are under a canopy.
ANY halfway accurate GPS-only distance measurement is inaccurate and will measure short. It's not the tree cover. That has some effect, but not the effect you think. No, because GPS distance measurement is measuring a bunch of straight line segments, it will ALWAYS shortcut corners. It's never measuring the full curve. You need a wheel sensor for that.
I use a wheel sensor to measure those curves and keep a distance log regardless of whether I ride through tunnels through the mtn and lose signal, whether I am riding in the open on flat ground, or whether I'm in the woods on hillsides that affect GPS reception more than the tree cover itself. When I ride with others who have wheel sensors, our total distances are usually within a couple hundredths of a mile of each other.
Not positive but is it possible strava calculates the distance with some algorithm that tries to match segments within the ride and if it is close enough, use those pre set values for your total? Like if you were riding parallel to a very popular 3 mile segment but you yourself did something different and did 3.25 miles, would strava assume gps issues and just assign you 3 miles and that you did the segment.
I have definitely seen strava display incorrect ride data and segments before. I recorded with my computer and someone else had their phone with strava. We both did the same ride but when I uploaded up to strava, the maps were pretty different. Mine being what we actually did and theirs being off.
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No, Strava doesn't do that level of processing on the fly. The app itself is processing the raw GPS data looking for outliers, just like every other app and device does. They all have slightly different ways of doing it, but they're all doing that work. None of it looks at segments or heat map data in real time. Though you can process a GPS file with a really cool tool they have that leverages that heatmap data. But it's way too resource-intensive to run that in real time while you're riding.
Is anything going to be 100% accurate?
Nope. Even my wheel sensor isn't 100% accurate. What it is, though, is a whole lot more consistent than GPS-only distance calculation.
