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<DIV id=idOWAReplyText39741 dir=ltr>
<DIV dir=ltr><FONT face=Arial color=#000000 size=2>Oops! The 5 mile radius
from those coordinates falls in the ocean, hence the results.
Doh! </FONT></DIV></DIV>
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<FONT face=Tahoma size=2><B>From:</B> Bill Tenbroeck<BR><B>Sent:</B> Mon
5/15/2006 6:15 AM<BR><B>To:</B>
postgis-users@postgis.refractions.net<BR><B>Subject:</B> Buffer
query<BR></FONT><BR></DIV>
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<DIV id=idOWAReplyText28613 dir=ltr>
<DIV dir=ltr><FONT face=Arial color=#000000 size=2>I am trying to generate a
query that will yield the areas of US blockgroups that fall within a 5-mile
radius of a point. The area should be clipped at the radius boundary, and only
return that portion within the buffer. My projection is Albers, North American.
It would *seem* that the sum of the resultant output would yield the area of a
circle with a 5 mile radius. (In square meters, I have calculated this to be a
bit over 203 million sq meters). However, my results are summing to a little
over 181 million sq meters.</FONT></DIV></DIV>
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<DIV> </DIV>
<DIV><FONT face=Arial size=2>The query I am using is:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>SELECT area(intersection(r.geom, buf_geom)) AS
clippedarea, area(r.geom) as totalarea, r.fips, '27653' as CID<BR>FROM
blkgrp_alb AS r, Buffer(GeomFromText('POINT(1919020.564
673785.6216)',102008),8046.72) buf_geom<BR>WHERE r.geom &&
buf_geom<BR>AND intersects(r.geom, buf_geom)<BR>order by fips</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Can anyone see either the flaw in the query or my
logic?</FONT></DIV>
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