Hi, I'm running AlpineQuest v1.1.3 on my HTC Desire and I've noticed something odd about how it shows the length of some tracks I recorded this weekend.
When I look at the list of tracks in "landmarks", it shows the length of a particular track (for example) as 6.92 miles.
When I long click and choose "details", the same track shows a total length of 6.15 miles (and a moving length of 6.12 miles).
Shouldn't all three numbers be the same?
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[closed] Distances don't match
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Re: Distances don't match
Hi,
Thanks for asking your question here.
You're right that in theory these numbers should be the same (at least the first 2 ones).
But in practice we are faced to inaccuracies that should be taken into account.
Here is the explanation:
The first distance of 6.92 miles is the "raw length" from the GPS, fastly computed and so displayed for each tracks in the landmark list. This is simply the sum of all successive location got from the GPS.
But these locations are not accurate, and if you go from a point A to a point B on a straightforward line, the GPS will locate you some times few feets on the left, then few feets on the right, and the final distance will be bigger than the shortest and real distance you've taken.
When you display the details window, the application tries to remove this extra length by correcting locations taking into account the previous and next location. This computation is longer than the simple sum of distances and is only done when displaying details. It is also displayed as "Length" is this window (but maybe another different name should be used), and is 6.15 miles in your exemple.
The last length just explude small moves: if you are stopped, the GPS can still locate you one feet in front, then one feet behind, etc which will increase the total lenght. The program tries to remove these extra length (and time) in the "moving" section.
Note that the same computations apply for the elevation.
I hope this ok for you now, and I will try to make things more clear in the application.
Best regards
Thanks for asking your question here.
You're right that in theory these numbers should be the same (at least the first 2 ones).
But in practice we are faced to inaccuracies that should be taken into account.
Here is the explanation:
The first distance of 6.92 miles is the "raw length" from the GPS, fastly computed and so displayed for each tracks in the landmark list. This is simply the sum of all successive location got from the GPS.
But these locations are not accurate, and if you go from a point A to a point B on a straightforward line, the GPS will locate you some times few feets on the left, then few feets on the right, and the final distance will be bigger than the shortest and real distance you've taken.
When you display the details window, the application tries to remove this extra length by correcting locations taking into account the previous and next location. This computation is longer than the simple sum of distances and is only done when displaying details. It is also displayed as "Length" is this window (but maybe another different name should be used), and is 6.15 miles in your exemple.
The last length just explude small moves: if you are stopped, the GPS can still locate you one feet in front, then one feet behind, etc which will increase the total lenght. The program tries to remove these extra length (and time) in the "moving" section.
Note that the same computations apply for the elevation.
I hope this ok for you now, and I will try to make things more clear in the application.
Best regards
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