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Elevation track algorithm

 
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waky



Joined: 29 Dec 2011
Posts: 2

PostPosted: Sat Apr 14, 2012 3:28 pm    Post subject: Elevation track algorithm Reply with quote

Ahoj,

I've exported tracklog from trekbuddy to GPX but if I import it to some app it almost always shows that I hiked about 1500m (one app shows 850m) but I know it was only about 700m. It was also shown only about 700m in trekbuddy. Can someone told me how trekbuddy counts "totally hiked"?
Or is this error because of GPX format? I've tried also export to NMEA but on my mobile (Samsung GT-B2710) the file was empty...
The tracklog was from bicycle.
Thanks for any suggestions.
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kruch
Site Admin


Joined: 02 Jul 2006
Posts: 5674

PostPosted: Sun Apr 15, 2012 12:05 pm    Post subject: Re: Elevation track algorithm Reply with quote

Info in the GPX is exactly what TB got from GPS, including altitude. So depeneding on how frequently points are logged and how smart the alg is, you may get very different results.

The value of asc-t which TB provides for CMS themes is using simple integration together with 50m threshold to filter deviations (can be rather significant especially with lower number of satellites in view).

Code:
on every location update:

    altDiff += (alt - altLast);

    if (altDiff >= 50F) {
       ascTotal += altDiff;
       altDiff = 0F;
    } else if (altDiff <= -50F) {
       descTotal += altDiff;
       altDiff = 0F;
    }

    altLast = alt;
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waky



Joined: 29 Dec 2011
Posts: 2

PostPosted: Mon Apr 16, 2012 5:26 am    Post subject: Reply with quote

Thanks! With this algorithm it shows 505m Smile
I will look better on this one.

Also I've find some "internal" (service) settings for GPS in my mobile. I will try to get NMEA data somehow. If it will be possible I will write it here on forum.
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Samimdyawe
Guest





PostPosted: Fri Aug 01, 2014 3:07 pm    Post subject: Reply with quote

I think that this information is the best.
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