GDAL's virtual raster capability allows you to supply a file (with extension VRT) specifying alterations or transformations to any GDAL-supported raster.
The changes are applied as the raster is read, meaning that a separate raster doesn't need to be created. This provides enormous flexibility - rasters can be:
- positioned (by creating position metadata)
- repositioned (by altering their position metadata)
- reprojected
- reduced (by taking spatial subsets or a subset of bands)
- modified (by altering data values)
The following page in the Eonfusion manual provides more information:
With the release (very soon!) of Eonfusion V2.0, the need to use virtual rasters will be greatly reduced. Eonfusion V2.0 allows access to the vertex attributes of raster data, which in turn enables operations such as repositioning and reprojection of rasters. Eonfusion will even handle reprojection automatically wherever it's implied by the raster's metadata.
Performing these operations within Eonfusion will be simpler in that it won't require the additional VRT file. It will also help to avoid some problems that arise when using virtual rasters.
These problems usually manifest as missing tiles, strange level-of-detail artifacts or even a complete absence of data that causes a raster to appear as a flat black rectangle.
If you are currently using GDAL virtual rasters with Eonfusion we recommend that when you upgrade to Eonfusion V2.0 you also upgrade your dataflows to use Eonfusion's raster manipulation capability wherever possible.
