<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=us-ascii">
<META content="MSHTML 6.00.6000.16481" name=GENERATOR></HEAD>
<BODY>
<DIV dir=ltr align=left><SPAN class=329305613-09092008><FONT face=Arial
color=#0000ff size=2>The srid of the geometry the identifier in the
spatial_reference_sys table that defines the datum, coordinates of your
geometry etc of the geometry in question). Spatial reference system
of the geometry. If your st_srid(the_geom) = -1 and you fed it to
distance_sphere/distance_spheroid, it wouldn't matter as long as your
coordinates are actually measured along the ellipsoid you specify (or
approximate ellipsoid of distance_sphere).</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=329305613-09092008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=329305613-09092008><FONT face=Arial
color=#0000ff size=2>The distance_sphere never takes a spheroid as I recall -
and always assumes a sphere and is faster than spheriod but less accurate.
</FONT></SPAN></DIV><SPAN class=329305613-09092008><FONT face=Arial
color=#0000ff size=2></FONT></SPAN><FONT face=Arial color=#0000ff size=2></FONT>
<DIV dir=ltr align=left><BR><SPAN class=329305613-09092008><FONT face=Arial
color=#0000ff size=2>Hope that helps,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=329305613-09092008><FONT face=Arial
color=#0000ff size=2>Regina</FONT></SPAN></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B>
postgis-users-bounces@postgis.refractions.net
[mailto:postgis-users-bounces@postgis.refractions.net] <B>On Behalf Of
</B>Willy-Bas Loos<BR><B>Sent:</B> Tuesday, September 09, 2008 8:56
AM<BR><B>To:</B> PostGIS Users Discussion<BR><B>Subject:</B> Re: [postgis-users]
why specify spheroid?<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=ltr>><SPAN><FONT face=Arial color=#0000ff size=2> distance_sphere
and distance_spheroid don't even look at the srid of the geometry fed to
them<BR>Why is that?</FONT></SPAN><BR></DIV></BODY></HTML>
<HTML><BODY><P><hr size=1></P>
<P><STRONG>
The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer.
</STRONG></P></BODY></HTML>
<P><hr size=1></P>
<P><STRONG><font size="2" color="339900"> Help make the earth a greener place. If at all possible resist printing this email and join us in saving paper. </p> <p> </font></STRONG></P>