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<font face="Times New Roman, Times, serif">Hi Rich,<br>
<br>
Topology is certainly the way to go: split all crossing
linestrings and create a new layer with the new, topologically
correct lines. Start- and endpoints of the new lines can be easily
found by interpolating from the original lines.<br>
<br>
I found the following links useful to start with PostGIS topology.
The documentation looks daunting, but it's really quite simple.
They all convert linstrings to topological polygons, but it would
not be too difficult to do the same for crossing linestrings to
topological linestrings.<br>
<br>
<a class="moz-txt-link-freetext" href="http://trac.osgeo.org/postgis/wiki/UsersWikiTopologyExample">http://trac.osgeo.org/postgis/wiki/UsersWikiTopologyExample</a> (Brent
Wood)<br>
<a class="moz-txt-link-freetext" href="http://strk.keybit.net/blog/2012/04/13/simplifying-a-map-layer-using-postgis-topology/">http://strk.keybit.net/blog/2012/04/13/simplifying-a-map-layer-using-postgis-topology/</a><br>
<a class="moz-txt-link-freetext" href="http://trac.osgeo.org/postgis/wiki/UsersWikiSimplifyPreserveTopology">http://trac.osgeo.org/postgis/wiki/UsersWikiSimplifyPreserveTopology</a><br>
<a class="moz-txt-link-freetext" href="http://trac.osgeo.org/postgis/wiki/UsersWikiSimplifyWithTopologyExt">http://trac.osgeo.org/postgis/wiki/UsersWikiSimplifyWithTopologyExt</a><br>
<br>
<br>
Cheers,<br>
<br>
Jan<br>
<br>
</font>
<div class="moz-cite-prefix">On 09/26/2012 03:43 AM, Richard
Greenwood wrote:<br>
</div>
<blockquote
cite="mid:CAHBySPZApcFo5OwNsz-7=jFBR0ECW_UzdqJDo539rtckp_2VwQ@mail.gmail.com"
type="cite">
<pre wrap="">I have a table of linestrings representing road centerlines. The
linestrings have the common "from" and "to" address min/max values.
But the linestrings are not broken at all of the intersecting streets.
So I need to break the linestrings at all intersections, but I need to
populate the "from" and "to" values appropriately in the new
linestrings. The addressing is based on line length. So I might start
with a linestring that goes from 100 to 500 and has two intersecting
streets. I break the original linestring into 3 new linestrings, but
how do I populate the "from" and "to" values? If I know the order of
the 3 new linestrings it would be very easy to calculate the new
values based on the length of each new linestring, eg. line #1
100-240, line#2 241-385, line #3 386-500 or some such thing.
It seems like something that topology should help with, but I'm not
sure where to start. Sorry if I haven't clearly defined my problem.
Any suggestions are appreciated.
Rich
</pre>
</blockquote>
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