[fixed] Distance and Elevation Calculation

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Xy()niX
Posts: 6
Joined: Sun Jun 20, 2010 11:12 pm

[fixed] Distance and Elevation Calculation

Post by Xy()niX » Sat Aug 28, 2010 4:12 pm

Hi Guys, I love the recent updates you've made to the software. But some of the functionality seems to be broken.

When recording a track I've noticed the software is not calculating the distance properly. It reads 0m. It happens particularly when I try to record additional waypoints inside the GPX file, but I also noticed that when recording a track without any additional waypoints after a few hours it stopped calculating the distance and reset it to 0. The elevation gain / loss has been displaying some strange data as well. The total elevation gain for instance seems to be correct, although it displays much more gain / loss than we actually did.

When I load my gpx files into Google Earth, all the information is there and displays correctly when displaying the elevation profile.

Let me know if I can provide you with additional information.

Cheers,

Psyberia-Support
Site Admin
Posts: 4895
Joined: Wed Apr 14, 2010 9:41 pm

Re: Distance and Elevation Calculation

Post by Psyberia-Support » Sat Aug 28, 2010 9:46 pm

Hi,
Concerning the elevation gain / loss, I already noticed this behavior. These values are computed as the sum of all elevation differences between each point pairs. I saw that my phone's GPS the elevation wasn't very stable and changed a lot. For example: 325m - 324m - 326m - 324m - 326m, will give +1m of total elevation, but +4m of elevation gain and -3m of loss for only 5 points! On tracks with hundreds of points, these values become quite high.
I'll try if using a threshold, or compute the elevation after a minimum distance will give more coherent values (and handle this accuracy problem on elevation).

Note also that the elevation of a point is only available if this point comes from the GPS (use 'lock map on current position' to save single waypoints with elevation). When moving manually the map, you lost the elevation information.

I didn't saw the "reset to 0" bug, I'll try to reproduce it or to find what could be the origin. I'll let you know about it.
Thanks a lot for all this information,
Regards
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Xy()niX
Posts: 6
Joined: Sun Jun 20, 2010 11:12 pm

Re: Distance and Elevation Calculation

Post by Xy()niX » Sun Aug 29, 2010 5:23 pm

Hi, thanks for looking into this.

Yes, I always use the lock map to current position and only use GPS (no network values) for positioning.

In regards to the distance, I noticed it immediately when starting to record a track then creating an additional waypoint. For instance I would set the software to record my track, then immediately create a waypoint called "trailhead". After this point it would continue to record my track but would display distance of 0m both on the main screen and in the details screen (long press on track / details). I figured the extra "Trailhead" waypoint I created was causing the problem, so I deleted the gpx file and started again without creating any extra waypoints. The software was correctly calculating the distance at first, so I locked the device and put it in my pack for a few hours. When I checked it again later it had reset to 0m distance.

We actually have 2 devices in our household, and 2 full versions of Alpine Quest. I am using a Nexus One, and my Wife is using an HTC Desire. We are experiencing the behavior on both devices.

Let me know if I can provide you with any additional data. I would be happy to help.

htcdesire
Posts: 1
Joined: Mon Aug 30, 2010 12:54 pm

Re: Distance and Elevation Calculation

Post by htcdesire » Mon Aug 30, 2010 1:06 pm

Hello,

I have the same problem. After recording a track, the only stats shown in "details" are time, the number of waypoints and altitude. The length is zero and the profile graph isn't drawn.

When loading the gpx file into another navigation program, the stats are complete. So the track is recorded properly.

Cheers

Psyberia-Support
Site Admin
Posts: 4895
Joined: Wed Apr 14, 2010 9:41 pm

Re: Distance and Elevation Calculation

Post by Psyberia-Support » Tue Aug 31, 2010 2:20 pm

Hi,
Thanks for your precisions.
I'm currently looking at this issue. I'll improve track recording/details a lot in next version.
Regards
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ukuest

Re: Distance and Elevation Calculation

Post by ukuest » Mon Sep 13, 2010 8:51 am

Actually the distance calculation of tracks works well in priciple, when you are recording at highest precision (1 fix/sec).

But then it suddenly jumps to 0 (zero) and stays there for the rest of the track.
This can happen after several kilometers, or immediately. It seemed random at first.

I think I have now found out when it happens: when you stop walking, and stay in the same place for some moments or minutes.

Maybe it is something simple like a division-by-zero error, when the same GPS location is recorded twice (=zero distance)?

I would be very happy if this bug could be fixed, because I like to know how far I have already hiked!
Otherwise, great work, am using AlpineQuest regularly now.

Psyberia-Support
Site Admin
Posts: 4895
Joined: Wed Apr 14, 2010 9:41 pm

Re: Distance and Elevation Calculation

Post by Psyberia-Support » Mon Sep 13, 2010 11:21 am

Hi,
ukuest you're absolutely right. Distance calculation fails between two identical coordinates (it doesn't compute 0 but a special number).
I never got tracks with 2 following identicals coords so I miss that (I usually use 1fix/5sec or 1fix/10sec when hiking).
I fixed it, this will be in 1.0.8 which will be released in few days.
Thanks a lot.
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ukuest

Re: Distance and Elevation Calculation

Post by ukuest » Wed Sep 15, 2010 8:04 am

I am so glad you could fix that!

Looking forward to the new version.

Psyberia-Support
Site Admin
Posts: 4895
Joined: Wed Apr 14, 2010 9:41 pm

Re: Distance and Elevation Calculation

Post by Psyberia-Support » Sun Sep 26, 2010 9:56 am

The "0m distance bug" has been fixed.
However the stats need some improvements, like filtering some erroneous GPX points. I'll try to do it soon.
Cam
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