<HTML><HEAD><TITLE>Re: [postgis-devel] Astronomical extensions</TITLE></HEAD>
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<DIV dir=ltr><FONT face=Arial color=#000000 size=2>Oops disregard my last email. I didn't read the bottom part and I no nothing about astronomy.</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2> Although I think sticking with a geometry and reference system makes sense instead of subclassing.</FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>The postgis geometry is pretty dumb actually in the sense that it assumes nothing about what is in it. E.g. you can have a geometry collection, point, multipoint, 3 dimensional multipoint etc. It really could care less.</FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>With that said - do not subclass, simply figure out how you will represent the ellipsis in the geometry field</FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>like </FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>Elipsis(...........)</FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>Then allow your application or find applications that already know how to deal with ellipsis or whatever kind of thing you are planning to store in.</FONT></DIV>
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<FONT face=Tahoma size=2><B>From:</B> Obe, Regina<BR><B>Sent:</B> Thu 10/26/2006 3:33 AM<BR><B>To:</B> PostGIS Development Discussion<BR><B>Subject:</B> RE: [postgis-devel] Astronomical extensions<BR></FONT><BR></DIV>
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<DIV dir=ltr><FONT face=Arial color=#000000 size=2>I think the first thing that comes to mind is that you'll need to define a spatial reference system for the area of space you are interested in. Not quite sure how to go about doing that. </FONT></DIV>
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<DIV dir=ltr><FONT face=Arial color=#000000 size=2>I'm not sure how you would do that for space, I imagine you'll need to define one for each area you are trying to use and then have some mechanism to switch the reference system as you switch into different areas of space. <FONT face=Arial size=2>You may want to ask an expert on Proj4, since I think Proj4 library is used internally by PostGIS.</FONT></FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>Actually come to think of it the SRID is kept with each geometry in the table, so all you would need to do is add the geometry field to a table, but do not constrain the reference system to a particular one. E.g. if you use the standard way of creating a geometry using addGeometry, then you'll need to destroy the SRID constraint.</FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>Unfortunately most tools assume that all the data that is loaded is in the same reference system, so you might want to look and see if someone has developed an application that reads the SRID from the row rather than from the geometry_columns table.</FONT></DIV>
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<DIV dir=ltr><FONT face=Arial size=2>Thanks,</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2>Regina</FONT></DIV>
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<FONT face=Tahoma size=2><B>From:</B> Michael Fuhr<BR><B>Sent:</B> Wed 10/25/2006 8:53 PM<BR><B>To:</B> PostGIS Development Discussion<BR><B>Subject:</B> Re: [postgis-devel] Astronomical extensions<BR></FONT><BR></DIV>
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<P><FONT size=2>On Wed, Oct 25, 2006 at 02:19:34PM -0700, Jim Bosch wrote:<BR>> I'm exploring the possibility of extending PostGIS to make it more<BR>> useful for astronomers (i.e. me), and I was interested in seeing if<BR>> anyone has any advice on how best to proceed (particularly in terms of<BR>> how to organize such things with the PostGIS internals).<BR><BR>You might wish to contact Oleg Bartunov, one of the PostgreSQL<BR>developers who maintains the GiST code; he's an astronomer too.<BR>Here's his web site, although it's not responding at the moment:<BR><BR><A href="http://www.sai.msu.su/~megera/" target=_blank>http://www.sai.msu.su/~megera/</A><BR><BR>Google probably has some of the site cached.<BR><BR>--<BR>Michael Fuhr<BR>_______________________________________________<BR>postgis-devel mailing list<BR>postgis-devel@postgis.refractions.net<BR><A href="http://postgis.refractions.net/mailman/listinfo/postgis-devel" target=_blank>http://postgis.refractions.net/mailman/listinfo/postgis-devel</A><BR></FONT></P></DIV>
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