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<font face="Arial">Hi Stewart,<br>
<br>
Thanks! I have just installed Quantum GIS (I'm running Ubuntu
10.10) and have loaded the JPEG as a raster file and am now
learning how do do what you suggested. <br>
<br>
Cheers,<br>
<br>
Peter<br>
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<div style="font-size: 8pt;"> <br>
Peter Freeman<br>
180 Musgrave Place<br>
Salt Spring Island, V8K 1V5<br>
British Columbia, Canada<br>
(250) 653-4623<br>
<a class="moz-txt-link-freetext" href="http://members.shaw.ca/petersfreeman">http://members.shaw.ca/petersfreeman</a><br>
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<br>
On 11-01-30 11:24 AM, Stewart C. Russell wrote:
<blockquote cite="mid:4D45BAD3.1090705@gmail.com" type="cite">
<pre wrap="">Hi Peter,
It's been a while since I hand-rolled a world file. If you can, install
a recent version of QGis, as it has a truly excellent georeferencer. You
click on control points on the bitmap, indicate the coordinates they
represent in the real world, then set the system off transforming the map.
</pre>
<blockquote type="cite">
<pre wrap="">The map file is called map.jpg and I have created a world file called
map.wld
</pre>
</blockquote>
<pre wrap="">
I'd call that map.jgw, which is the convention for JPEG world files.
(TIFF has tfw, PNG pgw, and so on.)
</pre>
<blockquote type="cite">
<pre wrap="">100.0
0.0
0.0
-100.0
103.5
1.5
</pre>
</blockquote>
<pre wrap="">
Ooh, that can't be right. Lines 1 and 4 are units/pixel; if you're using
geographic coordinates, that's 100°/pixel. This wants to be a small number.
</pre>
<blockquote type="cite">
<pre wrap="">Can you give me reasonably correct values for my world file?
</pre>
</blockquote>
<pre wrap="">
Lines 1 and 4 might want to be 0.01 and -0.01 respectively for 100
pixels/degree.
</pre>
<blockquote type="cite">
<pre wrap="">Do I need to create a projection file
</pre>
</blockquote>
<pre wrap="">
It helps, but these are even harder to produce by hand than world files.
I think that QGis can produce them in the georeferencer.
Stewart
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</pre>
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