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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Yes this is about spatial indexing
</span><span lang="EN-US" style="font-size:11.0pt;font-family:Wingdings;color:#1F497D">J</span><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"><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">Without looking at the actual VRT code I would guess that parsing the VRT file is one thing, but having a VRT file with +100,000 tiles would require
GDAL to look through each tile every time a pixel is requested?<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">Even, if your idea below could be implemented into the VRT driver to be able to build the index file and gdaladdo to build the overview index files,
it would be a huge step forward. <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">Is it possible to build the index on the fly into memory when opening the VRT file? Is it too memory or time consuming?<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">/Casper<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>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> gdal-dev [mailto:gdal-dev-bounces@lists.osgeo.org]
<b>On Behalf Of </b>Even Rouault<br>
<b>Sent:</b> 1. marts 2017 13:25<br>
<b>To:</b> gdal-dev@lists.osgeo.org<br>
<b>Cc:</b> Rahkonen Jukka (MML)<br>
<b>Subject:</b> Re: [gdal-dev] FW: Don't we have any ideas for GSoC 2017?<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p style="margin:0cm;margin-bottom:.0001pt"><span style="font-size:9.0pt;font-family:"Sans Serif","serif"">On mercredi 1 mars 2017 11:43:12 CET Rahkonen Jukka (MML) wrote:<o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0"><span style="font-size:9.0pt;font-family:"Sans Serif","serif"">> Forwarding to the list because Jordan's trial was not successful.<o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0">
<span style="font-size:9.0pt;font-family:"Sans Serif","serif""> <o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0"><span style="font-size:9.0pt;font-family:"Sans Serif","serif"">Sounds a good idea. I think potential students should be more pro-active in proposing and developing their own ideas.<o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0">
<span style="font-size:9.0pt;font-family:"Sans Serif","serif""> <o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0"><span style="font-size:9.0pt;font-family:"Sans Serif","serif"">Regarding "indexing on VRT files", I guess this is about spatial indexing of sources in a VRT file. My bet would be
that the size of VRT files that would need such indexing would be so large than their parsing would be the most limiting factor. But I can be wrong.<o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0"><span style="font-size:9.0pt;font-family:"Sans Serif","serif"">Some people who want to make a mosaic from a huge number of tiles do that by making VRTs of VRTs of VRTs with a pyramid
structure to avoid parsing a lot of XML and still having good performance.<o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0"><span style="font-size:9.0pt;font-family:"Sans Serif","serif"">Another option that has been mentionned in the past would be to have a variation of the VRT syntax that would reference
a tile index (shapefile or any OGR datasource) and would thus benefit from its spatial indexing & filtering capabilities<o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0">
<span style="font-size:9.0pt;font-family:"Sans Serif","serif""> <o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0"><span style="font-size:9.0pt;font-family:"Sans Serif","serif"">Something like:<o:p></o:p></span></p>
<p style="margin:0cm;margin-bottom:.0001pt;-qt-paragraph-type:empty;-qt-block-indent:0">
<span style="font-size:9.0pt;font-family:"Sans Serif","serif""> <o:p></o:p></span></p>
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<p style="margin:0cm;margin-bottom:.0001pt;-qt-block-indent:0;-qt-user-state:0"><span style="font-size:9.0pt;font-family:"Sans Serif","serif"">Even<o:p></o:p></span></p>
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