[GRASS-user] v.net.path problem (not the shortest route)

Jorge_de_Jesus · August 19, 2011, 9:16am

Hi to all

I've a question concerning v.net.path. I am probably missing something
obvious :-[

In the v.net.path example that I've posted yesterday
(http://rsg.pml.ac.uk/wps/example/index.html), if we put the car over
madrid and the destination in the node below Santa Maria (below Porto
city), the v.net.path uses a different route going thru Vigo. Therefore
picking a route that isnt the shortest.

A screenshot of the problem can be seen here: http://derp.co.uk/6de36

Basically it seems that v.net.path starts to pick the shortest path from
the 1st node to the 2nd node independently of the total route length
(therefore not checking if it is actually the shortest total path).

Any comments and suggestions ?!

Jorge

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Markus_GRASS · August 19, 2011, 9:29am

On Fri, Aug 19, 2011 at 11:16 AM, Jorge de Jesus <jmdj@pml.ac.uk> wrote:

Hi to all

I've a question concerning v.net.path. I am probably missing something
obvious :-[

In the v.net.path example that I've posted yesterday
(http://rsg.pml.ac.uk/wps/example/index.html), if we put the car over
madrid and the destination in the node below Santa Maria (below Porto
city), the v.net.path uses a different route going thru Vigo. Therefore
picking a route that isnt the shortest.

There were problems with the v.net.* modules in GRASS 6.4.0, maybe
also in 6.4.1. The v.net.* modules should be working correctly in
6.4.2, 6.5, and 7. Just in case you're using an older version of
GRASS.

Can you post 1) the full v.net command used to prepare the network, 2)
the output of v.net op=report, 3) the full v.net.path command? This
information should help to track down the problem.

Markus M

Markus_GRASS · August 19, 2011, 9:46am

On Fri, Aug 19, 2011 at 11:16 AM, Jorge de Jesus <jmdj@pml.ac.uk> wrote:

Hi to all

I've a question concerning v.net.path. I am probably missing something
obvious :-[

In the v.net.path example that I've posted yesterday
(http://rsg.pml.ac.uk/wps/example/index.html), if we put the car over
madrid and the destination in the node below Santa Maria (below Porto
city), the v.net.path uses a different route going thru Vigo. Therefore
picking a route that isnt the shortest.

A screenshot of the problem can be seen here: http://derp.co.uk/6de36

Basically it seems that v.net.path starts to pick the shortest path from
the 1st node to the 2nd node independently of the total route length
(therefore not checking if it is actually the shortest total path).

Any comments and suggestions ?!

Update:

One intersection is missing: run

v.clean in=graph out=graph_clean tool=break,rmdupl

rebuild network graph from vectors graph_clean and nodes, calculate
shortest path. That should give you the real shortest path.