Graham, You need to create the overlays (pyramids) for the virtual raster.
You can do it directly in QGIS: - Turn render off; - Load the Virtual raster; - Open Layer properties (right-click) and go to Pyramids - Select all the resolutions proposed and press Build pyramids. Or you can do it using GDAL in the terminal or comand line. Have a look here: http://linfiniti.com/2009/09/image-mosaicking-with-gdal/. there is also a great tutorial\testing in Portuguese, maybe you can understand it using a automatically translated version: http://translate.google.pt/translate?sl=pt&tl=en&js=n&prev=_t&hl=pt-PT&ie=UTF-8&u=http%3A%2F%2Fblog.viasig.com%2F2010%2F01%2Fmosaicos-de-imagens-em-mapserver-com-gdal%2F&act=url Hope this helps. Alexandre Neto On Thu, Dec 19, 2013 at 11:06 AM, Graham <[email protected]> wrote: > Hi, > > When using gdalbuildvrt to create a virtual raster, is there a way to > specify the scale dependent visibility of the vrt that is being created? > My reason for this question is that when displaying a vrt containing a > large > number of rasters QGIS 2.0.1 takes a very long time to open up the Layer > Properties dialogue. It would be therefore be a useful timesaver to set > the > visibility using the gdalbuildvrt command. > > > > -- > View this message in context: > http://osgeo-org.1560.x6.nabble.com/gdalbuildvrt-setting-scale-dependent-visibility-tp5095071.html > Sent from the Quantum GIS - User mailing list archive at Nabble.com. > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user >
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