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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi Paul.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I had to build a big vrt. The one trick that got it loading very fast into qgis was adding statistics to each rasterband:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> <Metadata><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> <MDI key="STATISTICS_MAXIMUM">255</MDI><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> <MDI key="STATISTICS_MEAN">111.6784426525</MDI><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> <MDI key="STATISTICS_MINIMUM">0</MDI><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> <MDI key="STATISTICS_STDDEV">52.100074055799</MDI><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </Metadata><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I just got stats from a subset and used that for all bands.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Duarte<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">De:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Paul Meems (Top-X) [mailto:p.meems@topx-group.nl]
<br>
<b>Enviada:</b> quinta-feira, 12 de Julho de 2012 12:11<br>
<b>Para:</b> gdal-dev@lists.osgeo.org<br>
<b>Assunto:</b> Re: [gdal-dev] Tiling aerial photos<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks Dmitry and Even,<br>
<br>
The aerial photos are north-up and are in the same projection and I think also in the same resolution.<br>
It are commercial aerial photos.<br>
<br>
The Correlator project sounds very interesting but not necessary in my case.<br>
I'll try to implement the VRT format and see what the performance will be.<br>
If it is fast we don't need to tile.<br>
<br>
Thanks,<br>
<br>
Paul <br>
<br>
2012/7/12 Even Rouault <<a href="mailto:even.rouault@mines-paris.org" target="_blank">even.rouault@mines-paris.org</a>><o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Selon "Paul Meems (Top-X)" <<a href="mailto:p.meems@topx-group.nl">p.meems@topx-group.nl</a>>:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">> Thanks Even,<br>
><br>
> <a href="http://www.gdal.org/gdalbuildvrt.html" target="_blank">http://www.gdal.org/gdalbuildvrt.html</a> does seems very interesting.<br>
> As I understand it, it will do the merging part (without actually merging).<o:p></o:p></p>
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<p class="MsoNormal">The VRT driver will do on-the-fly merging of tiles that have overlapping. The<br>
VRT itself is just a XML file.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
><br>
> But it doesn't do the tiling part, right?<o:p></o:p></p>
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<p class="MsoNormal">No, I wasn't sure if your photos were already regularly tiled or not. Note that<br>
the VRT accepts non regularly tiled images. They can have overlapping, gaps,<br>
different resolutions, etc. The main constraints are :<br>
- they are in the same projection<br>
- they are "north-up", that is to say there is no rotation or skewing term in<br>
their geotransform matrix<br>
- they have the same number of bands<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
> Or is the vrt so optimized tiling<br>
> is no longer necessary?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Not necessary. Note that the VRT has no internal spatial indexing, so if you<br>
have several dozains of thousands of images in a VRT, it might slow down because<br>
it will iterate over all the image descriptions (without needing to open them<br>
however, all the information is in the VRT) to see if they intersect with the<br>
request window. But I'd expect the number of images in the VRT to be really high<br>
for that effect to become noticeable.<br>
<br>
><br>
> Thanks,<br>
><br>
> Paul<o:p></o:p></p>
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<p class="MsoNormal">2012/7/12 Dmitry Baryshnikov <<a href="mailto:polimax@mail.ru" target="_blank">polimax@mail.ru</a>><o:p></o:p></p>
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<p class="MsoNormal">12.07.2012 14:36, Paul Meems (Top-X) пишет:<o:p></o:p></p>
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<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal" style="margin-bottom:12.0pt">Thanks Even,<br>
<br>
<a href="http://www.gdal.org/gdalbuildvrt.html" target="_blank">http://www.gdal.org/gdalbuildvrt.html</a> does seems very interesting.<br>
As I understand it, it will do the merging part (without actually merging).<br>
<br>
But it doesn't do the tiling part, right? Or is the vrt so optimized tiling is no longer necessary?<br>
<br>
Thanks,<br>
<br>
Paul <br>
<br>
<o:p></o:p></p>
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<p class="MsoNormal">2012/7/12 Even Rouault <<a href="mailto:even.rouault@mines-paris.org" target="_blank">even.rouault@mines-paris.org</a>><o:p></o:p></p>
<p class="MsoNormal">Selon "Paul Meems (Top-X)" <<a href="mailto:p.meems@topx-group.nl" target="_blank">p.meems@topx-group.nl</a>>:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
> Hi list,<br>
><br>
> I have several aerial photos and I use MapWindow GIS to view them.<br>
> MapWindow is already using GDAL v1.8<br>
><br>
> Instead of loading each aerial photo as an individual layer I want to<br>
> create a local tiles store of the photos.<br>
> I can then just load the tiles I need based on the scale and view. This<br>
> will most likely improve the performance.<br>
><br>
> The process will be something like this:<br>
> 1. Get the filenames of the photos<br>
> 2. Merge them into one<br>
> 3. Create tiles<br>
> 4. Put the tiles in a SQLite database<br>
><br>
> My first question: Is the above suggested process correct or should I do it<br>
> differently?<br>
> My second question: What GDAL functions should I look into to accomplish my<br>
> process?<o:p></o:p></p>
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<p class="MsoNormal">You could try to make a VRT from all your photos. It will be seen as a single<br>
GDAL dataset, and will take care of the burden of opening the underlying photos<br>
when needed. You can use the gdalbuildvrt utility to create the VRT from the<br>
photos.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
><br>
> Thanks,<br>
><br>
> Paul Meems<br>
> The Netherlands<br>
><br>
<br>
<o:p></o:p></p>
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<br>
<o:p></o:p></p>
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</blockquote>
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<p class="MsoNormal">There is an interesting work connected aerial imagery: <a href="http://trac.osgeo.org/gdal/wiki/Correlator" target="_blank">
http://trac.osgeo.org/gdal/wiki/Correlator</a><br>
<a href="http://correlatorgsoc2012.blogspot.com/" target="_blank">http://correlatorgsoc2012.blogspot.com/</a><br>
<br>
Best regards,<br>
Dmitry<o:p></o:p></p>
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