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#1
10-13-2017, 04:29 PM
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Different elevation results from two software makers
Why does MapMyRide and RideWithGPS give me fairly different elevation climbed results for every ride? Today was over 500 ft over 35 miles. Mileage is the same. Which do you think is more accurate?
__________________
It's not a new bike, it's another bike. 
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#2
10-13-2017, 05:13 PM
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#4
10-13-2017, 05:54 PM
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It may have to do with the method used to determine elevation gain/loss. Some devices rely on GPS positioning over an elevation profile top do that, some devices use barometric pressure change. It's possible that one activity tracking site wouldn't recognize a barometric pressure reading and default to GPS coordinate-based elevation while the other would use the pressure data from the GPS unit.
Or maybe it's just a difference in the algorithms they use to process those GPS data points and overlay them on to a map?
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#5
10-13-2017, 06:41 PM
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Garmin provides elevation profile based on it's electronic pressure sensor (or altimeter), and it's subject to the usual measurement uncertainty with these very sensitive devices. Garmin uses their own software buffering to keep the electronic altimeter from dancing around all day which could add up to a lot of error. In addition, they correct the electronic altimeter about every 15 minutes with a satellite reading while riding (or while the unit is on). This tends to mitigate errors do to changing atmospheric pressure over time.
Some outfits take the garmin data and repost it. I think Garmin has to approve the outfits before they do it. MapMyRide does not apparently have approval to do this (or an agreement, license or whatever). I am not sure about Strava but I believe they do have approval. I find the Strava data often is virtually the same as Garmin. The ones that do not repost Garmin data will overlay the route on a topographical map and with an algorithm, they determine the elevation gain (as mentioned in above post). Of course this method is usually the most inaccurate. RideWithGPS does this however, they supposedly use a more sophisticated algorithm with the latest topo map data. In the end, its not clear which method actually is the most accurate. It might even change from ride to ride, so it then becomes a question of which method is the most consistent. I think Garmin is the most accurate and repeatable. Even though two Garmin units might differ by a hundred or two feet, its not as much as error difference as we typically see from computing the gain by overlaying the GPS route on a topo map. Normalized Power data is much the same. Strava and MapMyRide do their oven weighted averaging, while Garmin and RideWithGPS use the standard sum of squares formula pioneered by the Training Peaks crew.
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#6
10-13-2017, 07:24 PM
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Quote:
__________________
It's not a new bike, it's another bike.
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#7
10-13-2017, 08:29 PM
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I use Garmin computer along with ether Strava or MapMyRide apps by phone. Garmin and Strava are very close for elevation/distance, MapMyRide reading for the same routes give me the most elevation/distance. So yeah, I trust Garmin/Strava more than MMR but quote MMR for bragging rights.
Last edited by bobswire; 10-13-2017 at 08:32 PM.
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