[Marble-devel] altitude profiles

[Arnd Baecker]

On Sun, 26 Sep 2010, Niko Sams wrote:

> Hi,
>
> I'd like to implement altitude profiles

Great - Very much looking forward to this!

> and would like to do a bit of
> brainstorming beforehand.
>
> * it should be an overlay widget showing the graph
> * it should read data either from a GPX file (if avaliable) or use
> locally avaliable SRTM data.
>  using a webservice might also be an option, but I haven't found a good one yet

Maybe 
http://wiki.openstreetmap.org/wiki/Route_altitude_profiles_SRTM
is helpful.
A server which provides altitudes for a given point (or list of points)
is http://www.geonames.org/export/web-services.html
(under "Elevation"). However, maximally only 20 points per request
are allowed.
Eg.: http://ws.geonames.org/astergdem?lats=50.01,51.01&lngs=10.2,11.2

In some mailinglist I found the remark, that
via the  Generic Mapping Tools one can generate
a height profile to a track by
   grdtrack track.txt -Gsrtm.grd > data.txt
(but I haven't used this myself)
Maybe some of the tools/code could be (re-)used.

For results from routing services it might be necessary
to add additional points along longer straight line
segments, where the altitude might change in between.

Best, Arnd