GDAL Supported Formats

http://www.remotesensing.org/gdal/formats_list.html

Selected 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

r.in.gdal will only operate correctly if the GDAL shared library is installed on the system and accessable (normally via LD_LIBRARY_PATH). If not, r.in.gdal will report Unable to initialize GDAL bridge. If this occurs it means that you either don't have GDAL installed (ie. libgdal.1.1.so), it isn't in the LD_LIBRARY_PATH, or it is the wrong version.

r.in.gdal uses a number of strategies to find the GDAL shared library. It first looks in $GISBASE/lib/. Then it looks for $GDAL_HOME and finally it searches without a path letting all the standard Unix dlopen() search rules apply (which normally includes LD_LIBRARY_PATH).

Location Creation

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

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

REFERENCES

AUTHOR

Last changed: $Date$