NAME¶

r.external - Link GDAL supported raster file to a binary raster map layer.

KEYWORDS¶

raster, import

SYNOPSIS¶

r.external r.external help r.external [-oerf] [input=name] [source=string] [ output=name] [band=integer] [ title="phrase"] [--overwrite] [-- verbose] [--quiet]

Flags:¶

-o

 

Override projection (use location's projection)

-e

 

Extend region extents based on new dataset

 

Also updates the default region if in the PERMANENT mapset

-r

 

Require exact range

-f

 

List supported formats and exit

--overwrite

 

Allow output files to overwrite existing files

--verbose

 

Verbose module output

--quiet

 

Quiet module output

Parameters:¶

input=name

 

Raster file to be linked

source=string

 

Name of non-file GDAL data source

output=name

 

Name for output raster map

band=integer

 

Band to select (default: all)

title=

 

Title for resultant raster map

DESCRIPTION¶

r.external allows a user to link a GDAL supported raster file to a binary raster map layer, from any GDAL supported raster map format, with an optional title. The file is not imported but just registered as GRASS raster map.

NOTES¶

In essence, r.external creates a read-only link to the original dataset which is only valid if the original dataset remains at the originally indicated directory and filename.

NULL data handling¶

GDAL-linked ( r.external) maps do not have or use a NULL bitmap, hence r.null cannot manipulate them directly. Here NULL cells are those whose value matches the value reported by the GDALGetRasterNoDataValue() function. To apply the GDAL-linked the user need to either create a MASK (e.g. with r.mask) and then "apply" it using e.g. r.resample, or use r.mapcalc to create a copy with the appropriate categories changed to NULL (if() condition).

EXAMPLES¶

RGB Orthophoto from GeoTIFF¶

# import of all channels (each channel will become a GRASS raster map): r.external /home/user/data/maps/059100.tif out=ortho g.region rast=ortho.3 -p d.rgb r=ortho.1 g=ortho.2 b=ortho.3 r.composite r=ortho.1 g=ortho.2 b=ortho.3 output=ortho.rgb

SEE ALSO¶

r.in.gdal, v.external

REFERENCES¶

GDAL Pages: http://www.gdal.org/

AUTHOR¶

Glynn Clements Last changed: $Date: 2013-12-20 18:52:08 +0100 (Fri, 20 Dec 2013) $ Full index © 2003-2014 GRASS Development Team