Extend the DEFAULT_WIND in PERMANENT mapset to include the region of
the new map layer. Old resolution is preserved, but the region, and rows/cols
are updated. This will fail if the user doesn't have write access to the
PERMANENT mapset.
GDAL Supported Formats
Full details on GDAL supported formats are available at:
http://www.remotesensing.org/gdal/formats_list.html
Selected formats of more than 20 supported formats:
Format Name Georeferencing
Arc/Info Binary Grid Yes
CEOS (Spot for instance) No
First Generation USGS DOQ Yes
New Labelled USGS DOQ Yes
Military Elevation Data (DTED) Yes
Eosat Fast Format No
ESRI .hdr Labelled Yes
TIFF / GeoTIFF Yes
Erdas Imagine .hfa No
JPEG JFIF No
PCI .aux Labelled Yes
Portable Network Graphics (PNG) No
USGS SDTS DEM Yes
SAR CEOS No
Location Creation
r.in.gdal attempts to preserve projection information when importing
datasets if the source format includes projection information, and if
the GDAL driver supports it. If the projection of the source dataset does
not match the projection of the current location r.in.gdal will
report an error message (Projection of dataset does not appear to
match current location) and then report the PROJ_INFO parameters of
the source dataset.
If the user wishes to ignore the difference between the apparent coordinate
system of the source data and the current location, they may pass the
-o flag to override the projection check.
If the user wishes to import the data with the full projection definition,
it is possible to have r.in.gdal automatically create a new location based
on the projection and extents of the file being read. This is accomplished
by passing the name to be used for the new location via the location
parameter. Upon completion of the command, a new location will have been
created (with only a PERMANENT mapset), and the raster will have been
imported with the indicated output name into the PERMANENT mapset.
Support for GCPs: In case the image contains GCPs they are written to a
POINTS file within an imagery group. They can directly be used for
i.rectify. The target option allows to
automatically re-project the GCPs from their own projection into another
projection read from the PROJ_INFO file of the location name
target.
NOTES
I plan to make a variety of improvements to r.in.gdal in the future
including support for reporting everything known about a dataset if the
output parameter is not set.
The r.in.gdal comand does support the following features, as long as
the underlying format driver supports it:
- Color Table
- Bands with associated colortables will have the color tables transferred.
Note that if the source has no colormap, r.in.gdal in GRASS 5.0 will emit
no colormap. Use r.colors map=... color=grey to assign a greyscale colormap.
In a future version of GRASS r.in.gdal will likely be upgraded to automatically
emit greyscale colormaps.
- Data Types
- Most GDAL data types are supported. Float32 and Float64 type bands
are translated as GRASS floating point cells (but not double precision ...
this could be added if needed), and most other types are translated as
GRASS integer cells. This includes 16bit integer data sources. Complex
(some SAR signal data formats) data bands are translated to two floating
point cell layers (*.real and *.imaginary).
- Georeferencing
- If the dataset has affine georeferencing information, this will be used
to set the north, south, east and west edges. Rotational coefficients will
be ignored, resulting in incorrect positioning for rotated datasets.
- Projection
- The datasets projection will be used to compare to the current location
or to define a new location. Internally GDAL represents projections in
OpenGIS Well Known Text format. A large subset of the total set of GRASS
projections are supported.
- Null Values
- Raster bands for which a null value is recognised by GDAL will have
the null pixels transformed into GRASS style nulls during import. Many
generic formats (and formats poorly supported by GDAL) do not have a way
of recognising null pixels in which case r.null should be used after the
import.
- GCPs
- Datasets that have Ground Control Points will have them imported as
a POINTS file associated with the imagery group. Datasets with only one
band that would otherwise have been translated as a simple raster map
will also have an associated imagery group if there are ground control points.
The coordinate system of the ground control points is reported by r.in.gdal
but not preserved. It is up to the user to ensure that the location
established with i.target has a compatible coordinate system before using
the points with i.rectify.
SEE ALSO
r.in.ascii,
r.in.arc,
r.in.bin,
r.null
REFERENCES
GDAL Pages: http://www.remotesensing.org/gdal/,
Precompiled libgdal for GRASS: http://gdal.velocet.ca/projects/grass
AUTHOR
Frank Warmerdam (warmerdam@pobox.com).
Last changed: $Date$