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<small><font size="+1"><small>Ken / Brett,<br>
<br>
The only thing we know for certain is that we are all out of our
depths! Regardless, I think we are on the way to solving this.<br>
<br>
Please find a new srs.db here <a class="moz-txt-link-freetext" href="http://dl.dropbox.com/u/9546967/srs.db">http://dl.dropbox.com/u/9546967/srs.db</a>.
The new file incorporates both towgs84 parameters and a reference to
the distortion files. The distortion file values appear to take
precedence, but I have included the towgs84 parameters as it looks like
the AGD84 distortion files do not cover the states and territories that
did not adopt AGD84. Note that I have changed the AGD66 towgs84
parameters to national ones (previously ACT) according to this document
(page 31) <a class="moz-txt-link-freetext" href="http://www.icsm.gov.au/gda/gdatm/gdav2.3.pdf">http://www.icsm.gov.au/gda/gdatm/gdav2.3.pdf</a>.<br>
<br>
To use the distortion files you need to place these files
<a class="moz-txt-link-freetext" href="http://dl.dropbox.com/u/9546967/agd66.gsb">http://dl.dropbox.com/u/9546967/agd66.gsb</a>
<a class="moz-txt-link-freetext" href="http://dl.dropbox.com/u/9546967/agd84.gsb">http://dl.dropbox.com/u/9546967/agd84.gsb</a> in your Proj data directory
(/usr/share/proj on Linux). It is the directory containing the 'epsg'
and 'proj_def.dat' files. Make sure that this is the directory your
Proj installation is actually using by checking the contents of the
PROJ_LIB environment variable (echo $PROJ_LIB). It may not be set,
which is OK. It took me about 4 hours to figure out I had set it to an
old development directory several years ago!<br>
<br>
Note that I did try it without the +wktext parameter. It works in Proj
(using cs2cs), but QGIS needs it.<br>
<br>
Let me know how it goes on your test points.<br>
<br>
Cheers,<br>
<br>
Roland<br>
<br>
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<div class="moz-signature">-- <br>
<strong><font face="Arial" color="#000080">ROLAND HILL</font></strong><br>
<strong><font face="Arial" color="#000080" size="2">Director</font></strong><br>
<strong><font face="Arial" color="#000080" size="2">Four Winds
Technology Pty Ltd</font></strong><br>
<strong><font face="Arial" color="#000080" size="2">Ph/Fax : +61
(0)2 6366 9425</font></strong><br>
<strong><font face="Arial" color="#000080" size="2">Mobile :
+61 (0)41 880 7472</font></strong><br>
<strong><font face="Arial" color="#000080" size="2"><a
href="mailto:Roland.Hill@fourwindstechnology.com.au">Roland.Hill@fourwindstechnology.com.au</a></font></strong>
<br>
<br>
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On 24/09/10 07:27, Ken Norris wrote:
<blockquote cite="mid:1285277235235-5564786.post@n2.nabble.com"
type="cite">
<pre wrap="">
Roland,
I incorporated your srs.db but the translation falls about 30m short (in
Melbourne) and about the same distance out at a control point in southern
Tasmania.
I see you use the National parameters that '... have an estimated accuracy
of about 1 metre.' and are most accurate around Canberra (surprise).
Geoscience recommend use of their distortion tables (xxx.gsb) for more
accurate work Australia-wide.
Can you incorporate the parameter reference to the distortion tables in the
srs.db? I, like Brett, am out of my depth here.
Regards
Ken
</pre>
</blockquote>
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