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<font size="+1"> Brett,</font><br>
<br>
Have a look at
<a class="moz-txt-link-freetext" href="http://blog.gmane.org/gmane.comp.gis.gdal.devel/month=20060301">http://blog.gmane.org/gmane.comp.gis.gdal.devel/month=20060301</a> for
another discussion on using AGD66 / AGD84. It basically describes how
the Proj4 definitions (which is where the Qgis CRS database comes from)
are not correct for AGD66 and AGD84. It also gives alternative
definitions a bit further down the discussion. You will notice how all
the AGD66 definitions have the same towgs84 parameters, as do the AGD84
definitions, but they are different for each datum. That's were the
shift from AGD66 to AGD84 should come from.<br>
<br>
Note that my understanding is that the towgs84 parameters supplied are
not definitive, but are only one possible set. That is why you will
gradually build up a set of alternative, say AGD84 Z57, definitions as
you open files from various sources - MapInfo may define it with one
set of towgs84 parameters while ESRI may use a different set. You may
even be asked to supply your preferred parameters if you get data
delivered from an airborne contractor in anything other than WGS84 (I
am a geophysicist too).<br>
<br>
I would test things by creating a custom CRS (Settings->Custom CRS)
using whichever of the definitions from the above link is appropriate
for your data. When you import/open your data (I can't quite recall
what exactly it is you where using) you should assign it to the Custom
CRS you created.<br>
<br>
If your Custom CRS database does not appear to be working properly (ie
you can see your custom CRS, but it isn't sticking to your data
properly), then try to find your custom CRS database (qgis.db in your
home directory on Linux, I guess it is in Application Settings or
something similar in Windows) and delete it in case you have an old one
with an incorrect format.<br>
<br>
The longer term fix is to install the correct, or at least 'a' correct,
version of the AGD66 and AGD84 definitions in the main crs database
(srs.db). While you could argue over which towgs84 parameters are
better, any would be preferable to the way it is now. The main and
custom CRS databases are SQLite3 databases. I might give this a go over
the next few days if I get a chance.<br>
<br>
Also, this page may help to explain some of the Proj4 parameters
<a class="moz-txt-link-freetext" href="http://trac.osgeo.org/proj/wiki/GenParms">http://trac.osgeo.org/proj/wiki/GenParms</a><br>
<br>
Hope this all makes sense - its getting late.<br>
<br>
Regards,<br>
<br>
Roland<br>
<br>
<div class="moz-signature"> <br>
<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>
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<br>
On 22/09/10 19:59, Brett Adams wrote:
<blockquote cite="mid:4C99D374.9000506@gmail.com" type="cite"> Gents,
<br>
Guess I'm wondering what the next step on this topic is. I don't know
what to do next.
<br>
<br>
Currently QGIS cannot separate ADG66/ AGD84 /GDA94 in either export or
import. If it can, then I haven't seen it and if its that fickle, its
way too dangerous for me.
<br>
<br>
Not keen on going to another package as they take time to learn. Is it
even an option to sponsor someone to sort this out for me?
<br>
<br>
Technically I'm way over my depth so can't offer many solutions myself.
<br>
<br>
I need some honest answers.
<br>
<br>
Thanks
<br>
<br>
</blockquote>
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