[postgis-users] Calculate driving distance in postgis

[Arnaud Lesauvage]

K Kuo a écrit :
> I have a database which convert from tiger/line data. I have found that I 
> can use distance_spheroid function to calculate distance between two points, 
> which supposes to be the shortest distance instead of driving distance, am I 
> correct? What I am thinking about is that I have to query out all nodes 
> alone the route, calculate distances for each segment then add them up. I 
> don't think this is a good approach. Any suggestion?

Hi !

I have successfully installed and used pgdijkstra, which is a 
PostgreSQL implementation of the Dijkstra algorithm (widely used 
for shortest path calculations).
http://www.cartoweb.org/contribs.html
It is very easy to install and fairly easy to use.
This module includes special PostGIS functions that can return the 
shortest path between two nodes as a PostGIS geometry (a 
LINESTRING, I believe).
You would just need to get the Length() of this geometry to have 
the exact driving distance between the nodes.

Regards
--
Arnaud