vector length

[Jianping Xu]

> 
> I agree that v.report does a good job, but what is really needed is a 
> program that gives "on-the-ground" distance measurements; that is, takes in
> to account rises and falls of elevation, so that we get TRUE distance 
> measurements, not just the distance along the smooth surface of an ellipsoid.
>
My friend Runxuan Zhao (rzhao at psupen.psu.edu) suggested to use r.volume
to get the distances of networks. To the "surface" distances, one may
consider the following:
	. rasterize the streams (or roads);
	. r.mapcalc 'surface resolution' using horizontal resolution, slope
	  and aspect, derived from elevation;
	. r.volume the surface resolution.

***
Jianping Xu					 
Center for Remote Sensing and Spatial Analysis	 Email: jianp at ocean.rutgers.edu
Rutgers University			 	 Phone: (908) 932-9631
New Brunswick, NJ 08903-0231			 Fax:   (908) 932-8644