NAME¶
gdalbuildvrt - gdalbuildvrt Builds a VRT from a list of datasets. (compiled by
default since GDAL 1.6.1)
SYNOPSIS¶
gdalbuildvrt [-tileindex field_name]
[-resolution {highest|lowest|average|user}]
[-te xmin ymin xmax ymax] [-tr xres yres] [-tap]
[-separate] [-b band] [-sd subdataset]
[-allow_projection_difference] [-q]
[-addalpha] [-hidenodata]
[-srcnodata "value [value...]"] [-vrtnodata "value [value...]"]
[-a_srs srs_def]
[-input_file_list my_liste.txt] [-overwrite] output.vrt [gdalfile]*
DESCRIPTION¶
This program builds a VRT (Virtual Dataset) that is a mosaic of the list of
input GDAL datasets. The list of input GDAL datasets can be specified at the
end of the command line, or put in a text file (one filename per line) for
very long lists, or it can be a MapServer tileindex (see
gdaltindex
utility). In the later case, all entries in the tile index will be added to
the VRT.
With -separate, each files goes into a separate
stacked band in the VRT
band. Otherwise, the files are considered as tiles of a larger mosaic and the
VRT file has as many bands as one of the input files.
If one GDAL dataset is made of several subdatasets and has 0 raster bands, all
the subdatasets will be added to the VRT rather than the dataset itself.
gdalbuildvrt does some amount of checks to assure that all files that will be
put in the resulting VRT have similar characteristics : number of bands,
projection, color interpretation... If not, files that do not match the common
characteristics will be skipped. (This is only true in the default mode, and
not when using the -separate option)
If there is some amount of spatial overlapping between files, the order may
depend on the order they are inserted in the VRT file, but this behaviour
should not be relied on.
This utility is somehow equivalent to the gdal_vrtmerge.py utility and is build
by default in GDAL 1.6.1.
- -tileindex:
- Use the specified value as the tile index field, instead of the default
value with is 'location'.
- -resolution
{highest|lowest|average|user}:
- In case the resolution of all input files is not the same, the -resolution
flag enables the user to control the way the output resolution is
computed. 'average' is the default. 'highest' will pick the smallest
values of pixel dimensions within the set of source rasters. 'lowest' will
pick the largest values of pixel dimensions within the set of source
rasters. 'average' will compute an average of pixel dimensions within the
set of source rasters. 'user' is new in GDAL 1.7.0 and must be used in
combination with the -tr option to specify the target resolution.
- -tr xres yres :
- (starting with GDAL 1.7.0) set target resolution. The values must be
expressed in georeferenced units. Both must be positive values. Specifying
those values is of course incompatible with highest|lowest|average values
for -resolution option.
- -tap:
- (GDAL >= 1.8.0) (target aligned pixels) align the coordinates of the
extent of the output file to the values of the -tr, such that the aligned
extent includes the minimum extent.
- -te xmin ymin xmax ymax :
- (starting with GDAL 1.7.0) set georeferenced extents of VRT file. The
values must be expressed in georeferenced units. If not specified, the
extent of the VRT is the minimum bounding box of the set of source
rasters.
- -addalpha:
- (starting with GDAL 1.7.0) Adds an alpha mask band to the VRT when the
source raster have none. Mainly useful for RGB sources (or grey-level
sources). The alpha band is filled on-the-fly with the value 0 in areas
without any source raster, and with value 255 in areas with source raster.
The effect is that a RGBA viewer will render the areas without source
rasters as transparent and areas with source rasters as opaque. This
option is not compatible with -separate.
- -hidenodata:
- (starting with GDAL 1.7.0) Even if any band contains nodata value, giving
this option makes the VRT band not report the NoData. Useful when you want
to control the background color of the dataset. By using along with the
-addalpha option, you can prepare a dataset which doesn't report nodata
value but is transparent in areas with no data.
- -srcnodata value
[value...]:
- (starting with GDAL 1.7.0) Set nodata values for input bands (different
values can be supplied for each band). If more than one value is supplied
all values should be quoted to keep them together as a single operating
system argument. If the option is not specified, the intrinsic nodata
settings on the source datasets will be used (if they exist). The value
set by this option is written in the NODATA element of each ComplexSource
element. Use a value of None to ignore intrinsic nodata settings on the
source datasets.
- -b band:
- (GDAL >= 1.10.0) Select an input band to be processed. Bands are
numbered from 1. If input bands not set all bands will be added to
vrt
- -sd subdataset
- (GDAL >= 1.10.0) If the input dataset contains several subdatasets use
a subdataset with the specified number (starting from 1). This is an
alternative of giving the full subdataset name as an input.
- -vrtnodata value
[value...]:
- (starting with GDAL 1.7.0) Set nodata values at the VRT band level
(different values can be supplied for each band). If more than one value
is supplied all values should be quoted to keep them together as a single
operating system argument. If the option is not specified, intrinsic
nodata settings on the first dataset will be used (if they exist). The
value set by this option is written in the NoDataValue element of each
VRTRasterBand element. Use a value of None to ignore intrinsic nodata
settings on the source datasets.
- -separate:
- (starting with GDAL 1.7.0) Place each input file into a separate
stacked band. In that case, only the first band of each dataset
will be placed into a new band. Contrary to the default mode, it is not
required that all bands have the same datatype.
- -allow_projection_difference:
- (starting with GDAL 1.7.0) When this option is specified, the utility will
accept to make a VRT even if the input datasets have not the same
projection. Note: this does not mean that they will be reprojected. Their
projection will just be ignored.
- -a_srs srs_def:
- (starting with GDAL 1.10) Override the projection for the output file. The
srs_def may be any of the usual GDAL/OGR forms, complete WKT,
PROJ.4, EPSG:n or a file containing the WKT.
- -input_file_list:
- To specify a text file with an input filename on each line
- -q:
- (starting with GDAL 1.7.0) To disable the progress bar on the console
- -overwrite:
- Overwrite the VRT if it already exists.
EXAMPLE¶
Make a virtual mosaic from all TIFF files contained in a directory :
gdalbuildvrt doq_index.vrt doq/*.tif
Make a virtual mosaic from files whose name is specified in a text file :
gdalbuildvrt -input_file_list my_liste.txt doq_index.vrt
Make a RGB virtual mosaic from 3 single-band input files :
gdalbuildvrt -separate rgb.vrt red.tif green.tif blue.tif
Make a virtual mosaic with blue background colour (RGB: 0 0 255) :
gdalbuildvrt -hidenodata -vrtnodata "0 0 255" doq_index.vrt doq/*.tif
AUTHOR¶
Even Rouault even.rouault@mines-paris.org