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I have a large number of small tiles merged into a single VRT. The rasters are only viewed at large scale, so only a few of them are visible at the same time. The map refresh in qgis is slowing down however, as the number of tiles in the vrt increases. Is there any indexing of raster possible in the vrt format itself or perhaps inside pyqgis (manipulating the raster layer that links to my .vrt).

underdark
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U2ros
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    Perhaps some of the answers in this post might help: Best way to manage large number of geoTiff rasters. – Joseph Nov 05 '15 at 10:48
  • Seen that. WMS is not an option, its a local desktop application... Also way too much time would be spent retiling additional tiles i think. – U2ros Nov 05 '15 at 10:50
  • Only other thing I could think of would be creating pyramids :) – Joseph Nov 05 '15 at 10:57
  • Also no use, the zoom level at which my raster are used is below the pyramidss, they're not even used. – U2ros Nov 05 '15 at 10:58
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    Your analysis is right and VRT does not support any kind of indexing. There is an open GDAL ticket about this https://trac.osgeo.org/gdal/ticket/5762. However, there may be a workaround. It should be possible to create a set of smaller .VRT files which contain a reasonable amount of images and then build another vrt from the first generation .VRT files. Sort of a hand written b-tree index. – user30184 Nov 05 '15 at 11:13
  • As a temporary workaround, i ll try with postgis raster... – U2ros Nov 05 '15 at 13:59
  • No good with postgis raster, theres no real support in qgis... db manager hangs. Im trying with a large VRT, hosting a bunch of smaller – U2ros Nov 06 '15 at 15:47
  • In the end, i went with larger tiles (equals less tiles) and ecw format. Its not scalable, but it works for our case. – U2ros Dec 23 '15 at 20:54

1 Answers1

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Summarizing the comments so this question can be marked as answered:

VRT does not support any kind of indexing. There is an open GDAL ticket about this http://trac.osgeo.org/gdal/ticket/5762. However, there may be a workaround. It should be possible to create a set of smaller .VRT files which contain a reasonable amount of images and then build another vrt from the first generation .VRT files. Sort of a hand written b-tree index.

ECW might be an alternative, depending on the use case.

underdark
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