Steve,<div>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. </div><div><br></div><div>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 time.</div>
<div><br></div><div>The tuple returned could be something like:</div><div>vertex_id, parent_vertex_id, cost</div><div><br></div><div>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).</div>
<div><br></div><div><br><br><div class="gmail_quote">On Sun, Feb 19, 2012 at 3:01 PM, Stephen Woodbridge <span dir="ltr"><<a href="mailto:woodbri@swoodbridge.com">woodbri@swoodbridge.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi all,<br>
<br>
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.<br>
<br>
Does this code return multiple contours in a single request? How?<br>
<br>
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.<br>
<br>
Thoughts?<br>
<br>
-Steve<br>
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