GDAL Virtual Raster (beta)
Open BetabetaVRT is GDAL se XML-beskrywing van 'n rasterdatastel. Ons verpak die VRT saam met 'n gerenderde GeoTIFF in 'n enkele ZIP (map.vrt.zip) — anders misluk gdalinfo/gdal_translate met "map.tif not found". Beta: voorlopig 'n enkele bandstel sonder oorsigte.
Sleutelkenmerke
Oor die VRT-formaat
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.
Watter program open VRT-lêers
Die volgende programme en toepassings kan GDAL Virtual Raster (beta) (.vrt.zip)-lêers wat uit OSM2CDR uitgevoer is, open, redigeer en daarmee werk:
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.
Wie gebruik VRT-kaarte
Hoe om VRT uit te voer
Hoe om dit ná uitvoer te open
- 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.
Gewilde kaarte in VRT
Kry GDAL Virtual Raster (beta)-kaartuitvoere
Laai professionele VRT-kaarte van OpenStreetMap af. Onmiddellike generering, enige gebied.