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Author	Thread: Distance too long
WPWoodJr Posts: 86	Distance too long Posted: 15 Mar 10 7:37 PM Yesterday I ran a measured mile out and back for a total of 2 miles. I had AllSport and BiM Active GPS both running at the same time on my Storm2 so these tracks are from the same run. Here is the track from AllSport: http://www.trimbleoutdoors.com/ViewTrip/644355 Here is the track from BiM loaded into AllSport via GPX: http://www.trimbleoutdoors.com/ViewTrip/644632 AllSport is reporting 2.06 miles run, while BiM is reporting 2.01, which is very close to the actual measured mile distance. In general, AllSport is reporting higher values than BiM - too high I think. If you look closely at the track on the maps, you can see why. AllSport's track is much more "wiggly" than BiM's. Any idea why this is happening? Perhaps Allsport records too many points, or needs a smoothing algorithm? [Reply][Quote]
WPWoodJr Posts: 86	Re: Distance too long Posted: 16 Mar 10 3:21 AM To illustrate this issue with "wiggly" tracks in AllSport making the reported distance too large, I tried out a smoothing algorithm on the AllSport track from above and posted it here: http://www.trimbleoutdoors.com/ViewTrip/645171 The smoothed track is 2.01 miles long like the BiM one, and doesn't wiggle all over the place. When I did the run, I ran a straight line. To smooth the track I took the average of the 5 lat/long readings surrounding a given point - the two before it, the point itself, and the two after. I'm not saying this is the best way, but it seems to work ok. [Reply][Quote]
WPWoodJr Posts: 86	Re: Distance too long Posted: 18 Mar 10 3:50 AM Hi guys, any thoughts on smoothing out the AllSport track so distance is recorded more accurately? [Reply][Quote]
kevin77 Posts: 1237	Re: Distance too long Posted: 18 Mar 10 4:51 AM Yeah, I think we need to increase the radius at which we gather points. Even better, we could possibly make it configurable and an advanced option. Currently I think it's at 3 meters, but I'll double check. [Reply][Quote]
WPWoodJr Posts: 86	Re: Distance too long Posted: 18 Mar 10 5:31 PM Don't you collect a data point every 1-2 secs? How is it based on radius? [Reply][Quote]
Bob Wold Posts: 890	Re: Distance too long Posted: 18 Mar 10 5:54 PM We do attempt to get a position ever second, but we discard them unless they cross a distance threshold. This allows us to avoid some GPS noise and also to reduce the data size associated with your workout. [Reply][Quote]
kevin77 Posts: 1237	Re: Distance too long Posted: 18 Mar 10 6:00 PM In addition, having a larger radius distance for recording points will give you "straighter" looking tracks, but if the radius distance is too large, it ends up cutting corners and your distance will be too short. It is very possible that if you used the BiM software on a short curvy path like this one their distance would be too short. That was reported by another user who ran around a park trail several times with a known distance per lap. There are four pretty tight corners in that loop, which makes it difficult to collect accurate data. [Reply][Quote]
WPWoodJr Posts: 86	Re: Distance too long Posted: 18 Mar 10 8:08 PM How did kayakgirl use 2713 calories during that run?!?!? Actually I tried cutting points out of the track I smoothed above and it didn't help. I cut out 1 out of every 2 and when that didn't help I cut 2 out of every 3 of the points. Smoothing by averaging worked but simply collecting less points did not. I will post the results of that tonight so you can see. [Reply][Quote]
Bob Wold Posts: 890	Re: Distance too long Posted: 18 Mar 10 9:32 PM good question on calories: could be a high weight? not sure. [Reply][Quote]
Logan Swapp Posts: 237	Re: Distance too long Posted: 18 Mar 10 11:44 PM Bob, you're so insensitive! [Reply][Quote]
Bob Wold Posts: 890	Re: Distance too long Posted: 19 Mar 10 12:06 AM haha, well that's just a theory. I suppose it could be a bug... any alternatives? [Reply][Quote]
WPWoodJr Posts: 86	Re: Distance too long Posted: 19 Mar 10 2:44 AM OK here's the same run, with 1/2 the data points removed. Its still "wiggly" and now reports a distance of 2.03 miles instead of 2.06. I think smoothing is the way to go not removing data points. Even removing 2/3 of the data points only gets you down to 2.02 miles. http://www.trimbleoutdoors.com/ViewTrip/648651 [Reply][Quote]
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