<br><br><div class="gmail_quote">2011/1/11 Markus Innerebner <span dir="ltr"><<a href="mailto:markus.innerebner@inf.unibz.it">markus.innerebner@inf.unibz.it</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi all,<br>
<br>
I need some information about driving_distance calculation function:<br>
<br>
1) the query point(source_id) has to be a vertex or can it be a 2D point that is mapped to the closest possible edge?<br></blockquote><div><br></div><div>Driving Distance functions starts with a vertex. (There is a wrapper function that takes coordinates as start and searches for the nearest vertex from the given point).</div>
<div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
2) what happens with edges, that are partially reached? (one vertex is reached in time, the other one is not)<br></blockquote><div><br></div><div>Driving Distance only cares about vertices, because it works like Dijkstra algorithm. You can take the vertices and write an SQL function for example, that returns you the edges ... or a polygon.</div>
<div> </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
3) is the entire network loaded into main memory for doing such a computation?<br></blockquote><div><br></div><div>This depends on your query. You can only select the network in your query that you think is relevant for your result. Usually you select a bounding box around your start point. It's easy to guess how large this area is, if you cost parameter is a distance. It's more difficult if you cost parameter is time for example. If your bounding box was too small, then your result might have the shape of a square.</div>
<div><br></div><div>Daniel</div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<br>
thanks for your answer<br>
<br>
best regards<br><font color="#888888">
<br>
Markus Innerebner<br>
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