[Qgis-user] QGIS-Merge or creat virtual raster files without losing definition?

[Jonathan Moules]

Hi Mick,
  QGIS is using a tool called GDALMerge to do the merging.

An alternative is to do it yourself in GDAL at the command line. It's
fairly simple.
Use the "OSGeo4W Shell" link that comes with QGIS.

Navigate to the directory that has the tif files in.
To merge all your tiffs together into a basic VRT you only need two lines:

*dir /b /s "C:\my data\lots of tiffs\*.tif" > "**C:\my data\lots of tiffs*
*\tiff_list.txt"*

That line (assuming it's windows; there's a Linux equivalent) basically
creates a list of all the tif files.
Then:

*gdalbuildvrt -input_file_list "C:\my data\lots of
tiffs\tiff_list.txt" "C:\my data\lots of tiffs\my_merged_data.vrt"*

That line turns it into a VRT file.

Cheers,
Jonathan



On 17 June 2014 13:32, Michael Bracken <mickbracken at me.com> wrote:

> I am new to QGIS and relatively new to GIS (so please be aware I am not
> that familiar with jargon).
>
> I am trying to merge several tiff files as either a virtual raster or a
> simple merge. Whichever way I try the resulting display appears to lose
> definition (even just a couple of the files).
>
> I have tried to set the options to no compression (merge rasters), and
> resolution set at highest for creating virtual raster, but street names and
> place names still become too  pixillated to read properly.
>
> This does not happen if I load all the files I wish to merge individually,
> but obviously I would rather work with the merged or virtual files.
>
> I am using QGIS 2.2.0 on a 2.5 GHz Intel Core i5 Mac, OSX 10.9.3.
>
> Would appreciate some help, please.
>
> Mick
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> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user
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