pgrouting calculate length of shortest travel time route

Question

I currently use the pgr_kdijkstraCost() function to calculate the travel times of a few origins and destinations. But I would also like to return the distance length of these trips. Is this possible? If so, how would you go about it?

If it is not possible for a k matrix, is it possible for a single origin and destination?

Answer 1

Just addressing the length question here. The pgRouting docs give an example of pgr_kdijkstraPath where the result includes the path geometry. Then you just need to use ST_Length on the output geometry.

Example from the docs to get the geometry:

SELECT id1 as path, st_astext(st_linemerge(st_union(b.the_geom))) as the_geom
  FROM pgr_kdijkstraPath(
                  'SELECT id, source, target, cost FROM edge_table',
                  10, array[4,12], false, false
            ) a,
            edge_table b
WHERE a.id3=b.id
GROUP by id1
ORDER by id1;

path |            the_geom
------+---------------------------------
    4 | LINESTRING(2 3,3 3,4 3,4 2,4 1)
   12 | LINESTRING(2 3,3 3,4 3)
(2 rows)

Therefore if you want length, just use st_length(st_linemerge(st_union(b.the_geom)))