Why wouldn't you use a nearest neighbor calculation as demonstrated here (using
DISTINCT ON)?
http://postgis.refractions.net/documentation/manual-svn/ST_DWithin.html
Keep in mind ST_DWithin and ST_Distance don't care about whether a geometry is
a line or polygon or point or collection or whatever. They will always
consider the minimum distance between 2 geometries.
ST_DWithin will use a spatial index where as ST_Distance will not. So for
ST_DWithin to work, you have to make the assumption,
the closest road to any point is no more than X units away. The bigger you
make the X, the less efficient the index search, but the less likely you will
leave a point out.
Hope that helps,
Regina
________________________________
From: [email protected]
[mailto:[email protected]] On Behalf Of
[email protected]
Sent: Monday, December 29, 2008 3:18 AM
To: [email protected]
Subject: [postgis-users] Dividing an area to closest line
Hallo
My first time writing here.
The case is that I need to find the closest road from every point in the
terrain. The roads are defined in "roadparts". The very best thing would be to
get polygons around every roadpart which I could use on other data to bind it
to the right road.
The only solution I can see is making a raster of small rektangels that I bind
to my roadparts using nearest neighbour-calculations.
My question is if someone has a more efficient and better solution.
Sorry for my bad english
Thanks
/Nicklas Avén
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