[GRASS-user] v.net.path problem(output seem to be airline distances instead of rout distances with multiple input points)

[Markus Metz]

Stefan Neumeier wrote:
>  Dear all,
>
> I am relatively new to GRASS so maybe I am just missing some important step
> in between.
> What I want to do is to calculate a "simple" distance matrix from x start
> points (polygon-raster centroids)
> to x end points (specific locations e.g. hospitals) based on a route
> network.
>
> In a first step I prepared the network so that every start- and end point
> lies on the network (via v.net, option connect).
> In a second step I created a point input textfile to use in v.net.path (ID
> startX startY endX endY) wit several thousand records.
>
> Testing the shortest path calculation for one, two or three coordinate pairs
> read in from the point input file works
> as one would expect and I get a new vector layer depicting the pathes from
> the start points to the end-points based on the
> road network.
>
> But if the number of points in the input point file exceeds 4 coordinate
> pairs GRASS  calculates all consecutive
> distances seemingly as airline distances instead of road based distances (In
> the output vector layer the pairs of points
> are connected with a straight line only).
>
This should be fixed in recent versions of GRASS [1,2]

Markus M

[1] http://josef.fsv.cvut.cz/wingrass/grass64/
[2] http://josef.fsv.cvut.cz/wingrass/grass65/