Hi Davide that is because of the variance in the measured points. As calculating the ascent and descent is summing up the absolutes of the deltas, the error will increase, too. Thus using a filter to smooth the elevation values is a good idea.
QLGT uses a median filter for that. The median filter will remove the local maximum within N points. Another strategy would be to introduce a threshold before accumulating a new delta. But that is not implemented, yet. Using SRTM data usually does not help much. This data is subject to noise, too. especially in mountain areas the exact position of a track point can make a huge difference in the elevation reading from SRTM. Oliver -------- Original-Nachricht -------- > Datum: Tue, 05 Feb 2013 11:03:21 +0100 > Von: solitone <[email protected]> > An: [email protected] > Betreff: Re: [Qlandkartegt-users] DEM projection string > Oliver Eichler ha scritto: > > Anyway, just ignore the warning an go on. Verify the result and if it is > > ok just accept it as is. > > Yes, everything seems fine when I proceed anyway. > > Now I just want to explore why track elevation is overestimated with > regard to both actual and Garmin Connect result. Perhaps filtering track > points might be useful to cancel fluctuations. > > Thanks, > Davide > > > ------------------------------------------------------------------------------ > Free Next-Gen Firewall Hardware Offer > Buy your Sophos next-gen firewall before the end March 2013 > and get the hardware for free! Learn more. > http://p.sf.net/sfu/sophos-d2d-feb > _______________________________________________ > Qlandkartegt-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/qlandkartegt-users ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Qlandkartegt-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/qlandkartegt-users
