My response on the pgrouting list.
-------- Original Message --------
Subject: Re: [pgrouting-users] How determining a path from two points
(X, Y) no node of the graph
Date: Fri, 06 Mar 2009 12:42:44 -0500
From: Stephen Woodbridge <[email protected]>
To: Pablo Velazco Villares <[email protected]>
CC: [email protected]
References: <[email protected]>
Pablo Velazco Villares wrote:
Hello colleagues,
I am starting my work with pgRouting, not work well with road
networks.
I need to know if possible or is there some function that supports
the analysis of route from fucking X, Y located on or near a given
edge.
ie not necesariametente, take into account two nodes or vertices
(start or end of an edge)
resuntante require that the path includes only a portion of the edge
source or target of the solution ... thank you all and hope to have
been sufficiently explicit ... because I am trying to communicate a
complex issue in a strange language
if someone can give me a hand with this, it will be very grateful
Paul,
You have to split the starting edge and ending edge and use the part you
need. postGIS has tools to do this. I don't have my postGIS manual in
front of me, but here are the basic steps:
pct := ST_line_locate_point(segment, point);
a2pct := ST_line_substring(segment, 0.0, pct);
pct2b := ST_line_substring(segment, pct, 1.0);
a2pct is the segment from the start of the line to the point and pct2b
is the segment from the point to the end of the line. You have to decide
which substring you need to use based on how things are connected in the
results.
-Steve
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