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Author	Thread: Trips - Accurate Average MPH
jdwilling Posts: 3	Trips - Accurate Average MPH Posted: 07 Mar 10 12:42 PM How is avereage MPH calculated? I ran/walked 4.57 miles in 1:06. The average speed was calcualted to be 7.5 MPH. Obviously this is not accurate, should be in the low 4s. Where I run and live there is limited cell coverage, not sure if that matters. Is the average speed calculated from all of the GPX points instead of doing a traditional calculation (D = R x T)? Any assistance would be appreciated. Here is the link, I think: http://www.trimbleoutdoors.com/ViewTrip/636093 [Reply][Quote]
kevin77 Posts: 1237	Re: Trips - Accurate Average MPH Posted: 07 Mar 10 4:57 PM The average speed is calculated as distance over active time (not total time). In your run it looks like you fell victim to some bad GPS reception. I see you were running along a two lane road with trees on each side (yeah there were some more open parts, but). Where did you have your phone while you were running? In your hand or in some pouch? I see you have a BlackBerry 8xxx. What model specifically? And on what carrier? [Reply][Quote]
jdwilling Posts: 3	Re: Trips - Accurate Average MPH Posted: 07 Mar 10 7:37 PM The Blackberry 8310 on AT&T was in my right front windbreaker pocket. What is the advantage of having that calculation on active time? Also, the route clearly shows where I cut through some woods to connect to dead end roads. This is where it shows me resting? How can it be resting while there is still movement? I am not trying to be overly critical. I think this is an awesome package. Thanks for your responses. John [Reply][Quote]
kevin77 Posts: 1237	Re: Trips - Accurate Average MPH Posted: 07 Mar 10 11:13 PM All those little yellow segments in your track line represent resting. It makes up nearly half of your trip. Having the average speed be calculated from your active time is how we've always done it. It helps in situations like road biking or running on streets and having to wait for traffic lights. Typically you don't end up with tracks looking like yours, however. GPS signals have both position and time values associated with them (or really it's all based upon timing). A certain point may happen to fall on the trail that you were running on, but it may be "behind" where it really should be, therefore making the distance between it and the previous point less, and therefore making your speed appear to be less and show up as resting. Some really odd things can happen with a bad GPS signal. One thing you can try is start off by holding your phone in your hand for the first five or ten minutes to give the GPS its best chance of acquiring a good fix. GPS recievers work off of "history". The longer they've been on, the more accurate they can get (assuming the information they've recieved since it's been on is accurate). I'm probably doing more rambling than making any sense. Oh, what was the weather like up there during your run? Cloudy or overcast? Or clear and sunny? The weather can also cause problems with the GPS signal. Or best advice right now is to try it again and play around with it. Try taking a look at it during various parts of your run. Try holding it in your hand during part of your run and see if that makes any difference. Good luck. Keep it up. Thanks for the interest and feedback. Let us know how it goes or if you have any other questions. [Reply][Quote]
jdwilling Posts: 3	Re: Trips - Accurate Average MPH Posted: 07 Mar 10 11:17 PM Thanks again for the info and no, you weren't rambling. You were making sense. It was a crystal clear sunny day, gorgeous. I'll try those suggestions. John [Reply][Quote]
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