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<DIV><SPAN class=832444515-11042007><FONT face=Arial size=2>I'm a little bit
confused about what functions deal with 3d verses 2d
geometries.</FONT></SPAN></DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial size=2>I noticed for
example that in my install - "POSTGIS="1.2.1" GEOS="3.0.0rc4-CAPI-1.3.3"
PROJ="Rel. 4.5.0, 22 Oct 2006" USE_STATS"</FONT></SPAN></DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial size=2>I have two extent
functions - one called <STRONG>Extent </STRONG>and one called
<STRONG>Extent3d</STRONG></FONT></SPAN></DIV>
<DIV><SPAN class=832444515-11042007><STRONG><FONT face=Arial
size=2></FONT></STRONG></SPAN> </DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial size=2>The extent function
always seems to return a box2d even if I call it with a 3d geometry. Well
since I don't have any 3d geometries as of yet I faked it by doing
this</FONT></SPAN></DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial size=2>SELECT
extent(force_3d(the_geom)) from mytable </FONT></SPAN></DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial size=2>Extent3d however
returns a box3d geometry regardless of whether my geometry is 2d or
3d.</FONT></SPAN></DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial size=2>The postgis online
manual says that <STRONG>extent</STRONG> returns a box3d which seems to
conflict with what I'm experiencing so I'm just wandering if my install is
somehow buggy or if the manual is wrong and why there is no mention of
<STRONG>extent3d</STRONG> (or is that meant to be undocumented because its
obsolete?)</FONT></SPAN></DIV>
<DIV><SPAN class=832444515-11042007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=832444515-11042007>
<DT><SPAN class=term>extent(geometry set)</SPAN></DT>
<DD>
<P>The extent() function is an "aggregate" function in the terminology of
PostgreSQL. That means that it operators on lists of data, in the same way the
sum() and mean() functions do. For example, "SELECT EXTENT(GEOM) FROM GEOMTABLE"
will return a BOX3D giving the maximum extend of all features in the table.
Similarly, "SELECT EXTENT(GEOM) FROM GEOMTABLE GROUP BY CATEGORY" will return
one extent result for each category.</P></DD></SPAN></DIV></DIV>
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