[pgrouting-dev] Driving Distance Help

Steve Horn steve at stevehorn.cc
Sun Feb 19 19:20:44 EST 2012

I've been working with the driving_distance function in pgRouting, and as
far as I can tell it is one contour at a time.

A possible way to improve the function is to make the result set a little
more useful. If I was able to follow a path from the centerpoint to the
extent of the contour via a tree structure I would be able to create one
contour for a maximum radius, then on the client derive countours for less

The tuple returned could be something like:
vertex_id, parent_vertex_id, cost

Another improvement to the function would be to return an extra edge past
the max cost (or make that an option). I think currently the algorithm will
not return any edges that put the total cost past the input cost parameter.
My thought is I could take the extra edge and then interpolate the point on
the line that meets my cost exactly (or, even better - have the algorithm
compute this).

On Sun, Feb 19, 2012 at 3:01 PM, Stephen Woodbridge <woodbri at swoodbridge.com
> wrote:

> Hi all,
> Since I wrote my own driving distance code years ago and have been happy
> with it, I have just now looked into how the pgRouting code works.
> Does this code return multiple contours in a single request? How?
> It looks like this code can only return a single contour for a single
> request. This means if I want say contours for 5, 10, 15 minutes that I
> have to make 3 requests which means fetching the data, building the graph
> and creating the contours all have to be processed 3 times. It seem that it
> would make more sense to setup the problem once and compute all the
> contours at once and return 3 results.
> Thoughts?
> -Steve
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Steve Horn
steve at stevehorn.cc
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