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Hi List, <br><br>I've encounter the following question in gis.stackexcange [0] which is a bit theoretical and interesting.<br><br>It has to do about coordinate shifting between gdal and two other commercial applications and I am too wondering whats happening.<br>
<br>I would be very interested If someone could provide an insightful answer on what is happening <br><br>Nikos</p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-size:14.399999618530273px;vertical-align:baseline;clear:both;word-wrap:break-word;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px;background-color:rgba(248,248,248,0.6)">
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[0] <a href="http://gis.stackexchange.com/questions/72173/huge-differences-between-results-for-7-param-datum-transform">http://gis.stackexchange.com/questions/72173/huge-differences-between-results-for-7-param-datum-transform</a><br>
<br>I'm trying to transform a WGS84 lat/lon point</p><pre style="margin-top:0px;margin-bottom:10px;padding:5px;border:0px;font-size:12px;vertical-align:baseline;overflow:auto;width:auto;max-height:600px;font-family:Consolas,Menlo,Monaco,'Lucida Console','Liberation Mono','DejaVu Sans Mono','Bitstream Vera Sans Mono','Courier New',monospace,serif;background-color:rgb(238,238,238);color:rgb(51,51,51);line-height:18px">
<code style="margin:0px;padding:0px;border:0px;vertical-align:baseline;font-family:Consolas,Menlo,Monaco,'Lucida Console','Liberation Mono','DejaVu Sans Mono','Bitstream Vera Sans Mono','Courier New',monospace,serif;color:rgb(34,34,34)">11d42'32.10629" E 5d12'56.75371" S
</code></pre><p style="margin:0px 0px 1em;padding:0px;border:0px;font-size:14.399999618530273px;vertical-align:baseline;clear:both;word-wrap:break-word;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px;background-color:rgba(248,248,248,0.6)">
in three different software packages (Proj4, GeoTrans and Leica GeoOffice) but I receive very big differences between the results - around few hundred meters in X and Y! Note that these variations appears only with 7 parameters not with 3.</p>
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<strong style="margin:0px;padding:0px;border:0px;vertical-align:baseline">Proj4</strong></p><blockquote style="margin:0px 0px 10px;padding:10px;border-width:0px 0px 0px 2px;border-left-style:dotted;border-left-color:rgb(203,212,200);font-size:14.399999618530273px;vertical-align:baseline;quotes:none;background-color:rgb(233,237,231);color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px">
<p style="margin:0px;padding:0px;border:0px;vertical-align:baseline;clear:both;word-wrap:break-word">cs2cs +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +to +proj=utm +zone=32 +ellps=clrk80 +towgs84=178.3,316.7,131.5,-5.278,-6.077,-10.9792,-19.166 +south +units=m +no_defs</p>
</blockquote><hr style="border:0px;color:rgb(221,221,221);background-color:rgb(221,221,221);min-height:1px;margin-bottom:20px;font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;font-size:14.399999618530273px;line-height:18px">
<p style="margin:0px 0px 1em;padding:0px;border:0px;font-size:14.399999618530273px;vertical-align:baseline;clear:both;word-wrap:break-word;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px;background-color:rgba(248,248,248,0.6)">
<strong style="margin:0px;padding:0px;border:0px;vertical-align:baseline">GeoTrans</strong></p><pre style="margin-top:0px;margin-bottom:10px;padding:5px;border:0px;font-size:12px;vertical-align:baseline;overflow:auto;width:auto;max-height:600px;font-family:Consolas,Menlo,Monaco,'Lucida Console','Liberation Mono','DejaVu Sans Mono','Bitstream Vera Sans Mono','Courier New',monospace,serif;background-color:rgb(238,238,238);color:rgb(51,51,51);line-height:18px">
<code style="margin:0px;padding:0px;border:0px;vertical-align:baseline;font-family:Consolas,Menlo,Monaco,'Lucida Console','Liberation Mono','DejaVu Sans Mono','Bitstream Vera Sans Mono','Courier New',monospace,serif;color:rgb(34,34,34)">Delta X 178.3
Delta Y 316.7
Delta Z 131.5
Rot X -5.278
Rot Y -6.077
Rot Z -10.9792
SF = -19.166 / 0.999980834 (0.000019166)
</code></pre><hr style="border:0px;color:rgb(221,221,221);background-color:rgb(221,221,221);min-height:1px;margin-bottom:20px;font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;font-size:14.399999618530273px;line-height:18px">
<p style="margin:0px 0px 1em;padding:0px;border:0px;font-size:14.399999618530273px;vertical-align:baseline;clear:both;word-wrap:break-word;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px;background-color:rgba(248,248,248,0.6)">
<strong style="margin:0px;padding:0px;border:0px;vertical-align:baseline">Leica GeoOffice</strong></p><p style="margin:0px 0px 1em;padding:0px;border:0px;font-size:14.399999618530273px;vertical-align:baseline;clear:both;word-wrap:break-word;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px;background-color:rgba(248,248,248,0.6)">
Screenshot: <a href="http://imgur.com/cOTRuQB" rel="nofollow" style="margin:0px;padding:0px;border:0px;vertical-align:baseline;text-decoration:none;color:rgb(53,141,170)" target="_blank">http://imgur.com/cOTRuQB</a></p><hr style="border:0px;color:rgb(221,221,221);background-color:rgb(221,221,221);min-height:1px;margin-bottom:20px;font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;font-size:14.399999618530273px;line-height:18px">
<p style="margin:0px 0px 1em;padding:0px;border:0px;font-size:14.399999618530273px;vertical-align:baseline;clear:both;word-wrap:break-word;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px;background-color:rgba(248,248,248,0.6)">
The results are respectively:</p><ol style="margin:0px 0px 1em 30px;padding:0px;border:0px;font-size:14.399999618530273px;vertical-align:baseline;list-style-position:initial;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px;background-color:rgba(248,248,248,0.6)">
<li style="margin:0px 0px 7px;padding:0px;border:0px;vertical-align:baseline;line-height:16px;word-wrap:break-word">800392 9422525</li><li style="margin:0px 0px 7px;padding:0px;border:0px;vertical-align:baseline;line-height:16px;word-wrap:break-word">
800306 9422840</li><li style="margin:0px 0px 7px;padding:0px;border:0px;vertical-align:baseline;line-height:16px;word-wrap:break-word">800941 9422891</li></ol><p style="margin:0px 0px 1em;padding:0px;border:0px;font-size:14.399999618530273px;vertical-align:baseline;clear:both;word-wrap:break-word;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;line-height:18px;background-color:rgba(248,248,248,0.6)">
I believe all the 3 packages use same mathematical methods for 7-param transform (Bursa-Wolf method). What could be the cause of this huge variation?</p></div></div>