[Qgis-user] Making a vector layer of raster files extent

[Andreas Neumann]

Hi Hakon,

The gdal-tool "gdaltindex" generates a shapefile with the boundaries of 
the rasters. (See http://www.gdal.org/gdaltindex.html) In a second step 
you can generate a virtual raster with the tool "gdalbuildvrt". This way 
all 95 rasters are still separate in the file system, but for the GIS it 
appears as a single file. (see http://www.gdal.org/gdalbuildvrt.html).

For performance reasons it is also recommended to build pyramids in all 
individual rasterfiles. You can use gdaladdo for this purpose 
(http://www.gdal.org/gdaladdo.html).

I think this is the easiest solution to your problem and it doesn't 
require scripting. It also works across several GIS, incl. QGIS, 
Mapserver, gvSig, etc.

In QGIS, there is a GUI to most of the GDAL-tools. The plugin is called 
"GdalTools". After installation there is an additional menu called 
"Raster". The gdalado command is called "Build Overviews". The 
"gdalbuildvrt" command is called "Build virtual raster catalogue". There 
is no equivalent to the first step, the "gdaltindex" command, though.

----

Actually it came to my mind that it would be very convenient if the 
GDAL-tools would allow a combined version of these three commands from 
one single GUI. Your problem is very common, so I think many people 
would benefit from such an additional tool, that would automatically 
build pyramids, the tindex and the virtual raster, in a single step.

Hope this helps,
Andreas

On 1/24/11 4:38 PM, HÅKON BORCH wrote:
> Helo
> I have a catalog of  95 rasters with DEM. Each time I want to use them 
> I have to load a lot of them to find the one I need that covers the 
> area I am interested in. Is there a way to generate a layer containing 
> polygons of the extent of each layer. I want to make this layer to 
> easy find which DEM i should load to a project.
>
> Or is there an other smart way to deal with a lot of heavy raster 
> files, without waitng and waiting and waiting for them to render.
> Best
> Håkon Borch
>
>
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