GDAL Virtual Raster (beta)
Open BetabetaVRT er GDALs XML-beskrivelse av et rasterdatasett. Vi pakker VRT-en sammen med en gjengitt GeoTIFF i én enkelt ZIP (map.vrt.zip) – ellers feiler gdalinfo/gdal_translate med «map.tif not found». Beta: foreløpig ett båndsett uten oversiktsbilder.
Hovedfunksjoner
Om VRT-formatet
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.
Hvilket program åpner VRT-filer
Følgende programmer og applikasjoner kan åpne, redigere og arbeide med GDAL Virtual Raster (beta) (.vrt.zip)-filer eksportert fra 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.
Hvem bruker VRT-kart
Slik eksporterer du VRT
Slik åpner du filen etter eksporten
- 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.
Populære kart i VRT
Få karteksporter i GDAL Virtual Raster (beta)
Last ned profesjonelle VRT-kart fra OpenStreetMap. Umiddelbar generering, uansett område.