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 <span dir="ltr"><<a href="mailto:even.rouault@mines-paris.org" target="_blank">even.rouault@mines-paris.org</a>></span><br><div class="im">Selon "Paul Meems (Top-X)" <<a href="mailto:p.meems@topx-group.nl">p.meems@topx-group.nl</a>>:<br>
<br>
</div><div class="im">> 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>
</div>The VRT driver will do on-the-fly merging of tiles that have overlapping. The<br>
VRT itself is just a XML file.<br>
<div class="im"><br>
><br>
> But it doesn't do the tiling part, right?<br>
<br>
</div>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<br>
<div class="im"><br>
> Or is the vrt so optimized tiling<br>
> is no longer necessary?<br>
<br>
</div>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<br><br><div class="gmail_quote">2012/7/12 Dmitry Baryshnikov <span dir="ltr"><<a href="mailto:polimax@mail.ru" target="_blank">polimax@mail.ru</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>12.07.2012 14:36, Paul Meems (Top-X)
пишет:<br>
</div><div><div>
<blockquote type="cite">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>
<br>
<div class="gmail_quote">2012/7/12 Even Rouault <span dir="ltr"><<a href="mailto:even.rouault@mines-paris.org" target="_blank">even.rouault@mines-paris.org</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Selon "Paul Meems (Top-X)" <<a href="mailto:p.meems@topx-group.nl" target="_blank">p.meems@topx-group.nl</a>>:<br>
<div>
<div><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?<br>
<br>
</div>
</div>
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.<br>
<div><br>
><br>
> Thanks,<br>
><br>
> Paul Meems<br>
> The Netherlands<br>
><br>
<br>
<br>
</div>
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<br>
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</blockquote></div></div>
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<br>
</div>
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