GDAL Virtual Raster (beta)
Open BetabetaVRT är GDAL:s XML-beskrivning av en rasterdatamängd. Vi packar VRT:en tillsammans med en renderad GeoTIFF i en enda ZIP (map.vrt.zip) – annars misslyckas gdalinfo/gdal_translate med "map.tif not found". Beta: en enda banduppsättning utan översiktsbilder tills vidare.
Viktiga funktioner
Om formatet VRT
VRT is a service format of GDAL: an XML file that contains no pixels but describes where they lie and how to read them. That is the usual way to stitch mosaics and redefine referencing without copying gigabytes of raster.
We hand over the VRT together with the raster itself: the map.vrt.zip archive holds the XML description and the rendered map as a GeoTIFF. That was done deliberately — a lone .vrt would refer to a file you do not have, and gdalinfo simply would not open it.
The XML records the WGS84 coordinate system, the georeferencing (corner coordinates and pixel size) and three RGB bands, each pointing at the corresponding band of the GeoTIFF. The format is in beta status: it is one set of bands with no overview pyramids, and the raster itself is a flattened picture of the map rather than vector layers.
Vilket program öppnar VRT-filer
Följande program och applikationer kan öppna, redigera och arbeta med GDAL Virtual Raster (beta)-filer (.vrt.zip) som exporterats från OSM2CDR:
Format specifications
- Open standard
- 2D only
- Lossless (no quality loss)
- No attributes
- Output: 1 file
- GDAL Virtual Raster (.vrt). XML descriptor referencing source rasters; lazy mosaicing without copying pixels.
Vem använder VRT-kartor
Så exporterar du VRT
Så öppnar du filen efter exporten
- Unpacking is a mandatory first step: map.vrt and map.tif must lie next to each other in the same folder, since the reference inside the XML is relative.
- GDAL — gdalinfo map.vrt will show the size, the referencing and the bands; gdal_translate will convert the set into GeoTIFF, PNG or COG.
- QGIS — Layer → Add Raster Layer and pick map.vrt; the layer will land in its place by coordinates.
- A mosaic — your own .vrt over several rasters is assembled with gdalbuildvrt out.vrt tile1.tif tile2.tif, if the map has to be stitched with other data.
- Editing by hand — VRT is plain XML: the path to the raster, the referencing and the band descriptions can be fixed in a text editor.
Populära kartor i VRT
Hämta kartexporter i GDAL Virtual Raster (beta)
Ladda ner professionella VRT-kartor från OpenStreetMap. Direktgenerering, valfritt område.