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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi Joe,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If you are working on windows you can get
a newer version of the tools (that are in fwtools) using the awesome osgeo4win downloader
<a href="http://download.osgeo.org/osgeo4w/osgeo4w-setup.exe">http://download.osgeo.org/osgeo4w/osgeo4w-setup.exe</a><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>There are many ways to do this but if I
where to do this I would (to avoid overhead with scripting etc) import the data
(points and the census blocks) into a spatialite database ( see <a
href="http://www.gaia-gis.it/gaia-sins/">http://www.gaia-gis.it/gaia-sins/</a> )
using ogr2ogr <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>(or the spatialite gui tools)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>and then using the spatilalite gui and run
a spatial intersect query that will give you your results. For example something
like this:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>select id. census blocks , id. yourpoints from
censusblocks, yourpoints where censusblocks.the_geom && yourpoints.the_geom
and intersects (censusblocks.the_geom, yourpoints.the_geom);<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The same can be done with postgis almost
identically but then you have a little more overhead to install the postgresql/
postgis etc to get this done.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Cheers<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Karsten <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> fwtools-bounces@lists.maptools.org
[mailto:fwtools-bounces@lists.maptools.org] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Chaitanya kumar CH<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, March 19, 2012 1:40
AM<br>
<b><span style='font-weight:bold'>To:</span></b> Joe McMichael<br>
<b><span style='font-weight:bold'>Cc:</span></b> fwtools@lists.maptools.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [FWTools] Point in
polygon</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Joe,<br>
<br>
First note that FWtools for Windows is very old and not recommended.<br>
<br>
It is easy to write a python script that cycles through the coordinates and
select the census block after applying a filter. We can also cycle through the
blocks and get the set of coordinates and then use the OGRGeometry::Contains
method to confirm.<br>
<br>
The problem here is that there is no straight forward way to use spatial
indexes.<br>
<br>
There may be other options, like PostGIS, depending on your exact requirements.<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>On Mon, Mar 19, 2012 at 4:20 AM, Joe McMichael <<a
href="mailto:joemcmichael@gmail.com">joemcmichael@gmail.com</a>> wrote:<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
Hello GIS folks!<br>
<br>
I have a large number of lat/lon coordinates(120 million) that I would like to
know which census block they fall into. Can FWtools be used to crosswalk points
to polygons? Maybe you know of a better method?<br>
<br>
Thanks in advance for your advice.<font color="#888888"><span style='color:
#888888'><br clear=all>
<br>
<span class=hoenzb>Joe</span><br>
</span></font><br>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
<br clear=all>
<br>
-- <br>
Best regards,<br>
Chaitanya kumar CH.<br>
<br>
+91-9494447584<br>
17.2416N 80.1426E<br>
<br>
<br>
<br>
<br>
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