[GRASSLIST:3368] Re: Calculating cumulative change in elevation.

[Roger Miller]

On Sunday 24 March 2002 20:21, Ben Logan wrote:

> I have a raster elevation map (imported DEM) and a vector map
> representing roads.  I would like to use the elevation data to find
> the total (cumulative) distance you would ascend/descend in traversing
> a particular line.  Note that I'm not talking about just the
> difference in elevation between the start and end points.  Also, the
> vector map would only contain the one path to follow.
>
> Can anyone suggest a way to do this in GRASS?

Well, if you just accumulate the change in elevation along any route then 
your result will be equal to the difference between your beginning and ending 
elevations, so i suspect you mean something else.  Do you mean to produce two 
values, one for ascent and one for descent?

You might be able to do something with r.cost.  You would need to construct a 
raster map that gives the change in elevation along the road.  It wouldn't be 
at all straight foreward.


Roger Miller