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<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA">This will probably seem like a very weird request…<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA"><o:p> </o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA">What I am interested in doing is using GIS software to map an imaginary planet.<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA"><o:p> </o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA">My starting point is a number of raster images in different projections that cover parts of the planet (e.g. Robinson projection for a world map, different projection for larger-scale maps). I want to be able to integrate and overlay these images, then create vector shapefiles. I’m only concerned with surface mapping (no elevation modeling), at least for now.<o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA"><SPAN style="mso-spacerun: yes"> </SPAN><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA">The imaginary world is perfectly spherical, but a different size from Earth. Hence, to georeference my images, I need a GIS program that allows user-defined datums. <o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA"><o:p> </o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA">I have been investigating the GeoTiff file format, and (through the Listgeo and geotifcp utilities), it has all the machinery that I need to create an imaginary datum, a map projection and to attach the datum and projection to an image. However, I haven’t been able to find a software package that can actually interpret and make use of this specialized GeoTiff information. </SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA">Which free or low-cost GIS software packages can utilize Geotiff's capability for user-defined datums?</SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA"><o:p> </o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN lang=EN-CA style="mso-ansi-language: EN-CA">Thanks for any help!<o:p></o:p></SPAN></P></DIV>