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Author	Thread: Average speed calculation is incorrect
WPWoodJr Posts: 86	Average speed calculation is incorrect Posted: 08 Mar 10 5:04 AM The average speed is calculated as "distance"/"active time". If you are running and walk a significant amount then the walking time is (correctly) counted as "rest time" not "active time" but the distance walked is included in the average speed calculation. Can this be corrected please? [Reply][Quote]
WPWoodJr Posts: 86	Re: Average speed calculation is incorrect Posted: 08 Mar 10 2:47 PM Here is a trip that illustrates the problem: http://www.trimbleoutdoors.com/ViewTrip/637723 On this trip I walked .125 miles then ran back .125 miles. My average speed is listed as 12.3 mph because the average speed is calculated including the walking portion of the trip, as follows: Distance: .25 Total: 0:04:02 Active: 0:01:14 Resting: 0:02:48 Average Speed = .25/01:14*60 = 12.2 (rounding error?) My average speed should be approximately .125/01:14*60 = 6.1 Interestingly, on the phone this trip is shown with an average speed of 7.8 mph. I'm not sure how the phone is doing its calculation. [Reply][Quote]
Bob Wold Posts: 890	Re: Average speed calculation is incorrect Posted: 08 Mar 10 5:21 PM Thanks for pointing that out. We will add this to the list. You are totally right: if you are going to use active time, you need to use active distance. -Bob [Reply][Quote]
WPWoodJr Posts: 86	Re: Average speed calculation is incorrect Posted: 08 Mar 10 10:11 PM I would think this could be fixed pretty quickly on the web site vs any fix required for the phones, correct? :-) [Reply][Quote]
Bob Wold Posts: 890	Re: Average speed calculation is incorrect Posted: 09 Mar 10 4:37 PM Absolutely, this is way easier to fix on the web. We'll get it in there. BTW: does the math on the phone match the web? I thought the phone did properly do (active distance)/(active time). If not we'll plan to update this in both places. Thanks. [Reply][Quote]
WPWoodJr Posts: 86	Re: Average speed calculation is incorrect Posted: 10 Mar 10 4:15 AM The math on the phone is weird. I still haven't figured it out. For the run referenced above it was 7.8 mph average, still too high but I don't understand why. [Reply][Quote]
Bob Wold Posts: 890	Re: Average speed calculation is incorrect Posted: 10 Mar 10 6:37 PM I think that average speed sounds pretty reasonable for your example trip. Your thinking you had .125 miles of active distance, and you know you have 74 seconds of active time, so that would be the 6.1mph average speed that you expected, but if the actual distance considered active was .160 miles, then you would come up with the 7.8mph for average speed. And since the difference between .125 and .16 is only 186ft, that's really not that big of a difference. In theory you should be able to verify with a slightly longer trip because the ratio of error in distance to total distance would be a lot less and so your average speed would look even more accurate when you go further. We have a guy looking into fixing the average speed on the server side now, but it's not as trivial to fix as you would imagine :-) We'll keep you posted. If you try more and find that the average speed is too far off let me know and we'll look at closer on the handset also. Thanks for the thorough feedback! [Reply][Quote]
WPWoodJr Posts: 86	Re: Average speed calculation is incorrect Posted: 15 Mar 10 12:26 AM Hi Bob, The handset is calculating the average speed the same way as the web site ("total dist"/"active time" instead of the correct way "active dist"/"active time"). However the handset will sometimes report a lower average speed than the web site because the handset will not report an average speed higher than the "max speed". Take a look at this trip: http://www.trimbleoutdoors.com/ViewTrip/643485 On this trip the max speed was 9.4 mph (probably due to a slightly inaccurate gps reading). The average speed reported by the handset was always the same as the max speed until "total distance"/"active time" went below the max speed. I stopped as soon as this happened. The average speed is reported on the handset as 8.5, same as the web site. There is no way was I going that fast (I was in loafers lol). In the previous track above where the average speed on the handset was reported as 7.8 and reported as 12.3 on the web site, the reason for the discrepancy was that the max speed on the handset was 7.8. Does that make sense to you? - Bill [Reply][Quote]
Bob Wold Posts: 890	Re: Average speed calculation is incorrect Posted: 15 Mar 10 5:46 AM That makes sense, great observation! I'll discuss this with the guys and see what we can do. [Reply][Quote]
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