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<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial>Brent,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial>Is your data 2D or 3D? You might want to try out the new
ST_DelaunayTriangles in 2.1</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial><A
href="http://www.postgis.org/documentation/manual-svn/ST_DelaunayTriangles.html">http://www.postgis.org/documentation/manual-svn/ST_DelaunayTriangles.html</A></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial>Right now I beleive it's just 2D, but work is going on in GEOS
land to make it 3D.: <A
href="http://trac.osgeo.org/geos/ticket/570">http://trac.osgeo.org/geos/ticket/570</A></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial> It does require upgrading your system to 2.1 development
and Geos 3.4.0 dev so might not be an option for you
yet.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial>We also have windows build bot builds for those on
windows who want to try which gets built whenever there is a change in the 2.1
code base</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial><A
href="http://www.postgis.org/download/windows/experimental.php">http://www.postgis.org/download/windows/experimental.php</A>
(for 9.2 both 32-bit/64-bit and for 9.0,9.1 just 64-bit
windows)</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial>Hope that helps,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial>Regina</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial><A
href="http://www.postgis.us">http://www.postgis.us</A></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=949094204-01092012><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV><BR>
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<HR tabIndex=-1>
<FONT size=2 face=Tahoma><B>From:</B>
postgis-users-bounces@postgis.refractions.net
[mailto:postgis-users-bounces@postgis.refractions.net] <B>On Behalf Of
</B>pcreso@pcreso.com<BR><B>Sent:</B> Friday, August 31, 2012 11:42
PM<BR><B>To:</B> PostGIS Users Discussion<BR><B>Subject:</B> [postgis-users]
Concave hull problem & delaunay triangulation -help needed
please<BR></FONT><BR></DIV>
<DIV></DIV>
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD vAlign=top>Hi,<BR><BR>I'm trying to come up with an approach using
Postgis to come up with a polygon representing the outer bounds of a set
of points, ie: a polygon passing through all the outer points.<BR><BR>Much
useful info (as usual - thanks guys!!) at spatialdbadvisor & bostongis
but my limited understanding is stalling progress for now.<BR><BR>I came
across the ST_Concavehull() function, which fails. Indeed, I was surprised
to see this actually expands the polygon extent representing the point
set, as shown at:<BR><A
href="http://www.bostongis.com/postgis_concavehull.snippet">http://www.bostongis.com/postgis_concavehull.snippet</A>
as this buffers the points in some cases, and often gives quite unexpected
(to me anyway) results. <BR><BR>Looking for something that fits better,
using existing capabilities, I figured I could pretty easily use Delaunay
triangulation to create the outer hull, then realised this bridges every
second outer point (pretty much by definition). That's easy, just remove
any triangles from the polygon where they share a line segment with the
polygon. I like Postgis!!<BR><BR>I have Simon's code working fine, at
least using his example invocation, from:<BR><A
href="http://www.spatialdbadvisor.com/postgis_tips_tricks/290/r-based-delaunay-triangulation-function-for-postgis-using-the-deldir-package">http://www.spatialdbadvisor.com/postgis_tips_tricks/290/r-based-delaunay-triangulation-function-for-postgis-using-the-deldir-package</A><BR><BR>But
I can't figure out how to make it work with my point data. I don't know R
or PL/R well enough to adapt it.<BR><BR>I have a set of sample points in a
table:<BR><BR><FONT face=courier,monaco,monospace,sans-serif> Column
| Type
|
<BR> --------+-----------------+-----------------<BR>
id |
integer | not null
default<BR> geom | geometry(Point) | </FONT><BR><BR>Can
anyone explain, ideally in words of one syllable or less, how Simon's
function from the link above needs to be adapted to read my points dataset
as input?<BR><BR>Once I get the triangles as an output set I can use
Postgis for the rest...<BR><BR>Thanks,<BR><BR> Brent
Wood<BR><BR><BR></TD></TR></TBODY></TABLE></BODY></HTML>