AAIGrid – Arc/Info ASCII Grid

Driver short name

AAIGrid

Supported for read and write access, including reading of an affine georeferencing transform and some projections. This format is the ASCII interchange format for Arc/Info Grid, and takes the form of an ASCII file, plus sometimes an associated .prj file. It is normally produced with the Arc/Info ASCIIGRID command.

The projections support (read if a *.prj file is available) is quite limited. Additional sample .prj files may be sent to the maintainer, warmerdam@pobox.com.

The NODATA value for the grid read is also preserved when available in the same format as the band data.

By default, the datatype returned for AAIGRID datasets by GDAL is autodetected, and set to Float32 for grid with floating point values or Int32 otherwise. This is done by analysing the format of the NODATA value and, if needed, the data of the grid. From GDAL 1.8.0, you can explicitly specify the datatype by setting the AAIGRID_DATATYPE configuration option (Int32, Float32 and Float64 values are supported currently)

If pixels being written are not square (the width and height of a pixel in georeferenced units differ) then DX and DY parameters will be output instead of CELLSIZE. Such files can be used in Golden Surfer, but not most other ascii grid reading programs. For force the X pixel size to be used as CELLSIZE use the FORCE_CELLSIZE=YES creation option or resample the input to have square pixels.

When writing floating-point values, the driver uses the “%.20g” format pattern as a default. You can consult a reference manual for printf to have an idea of the exact behaviour of this ;-). You can alternatively specify the number of decimal places with the DECIMAL_PRECISION creation option. For example, DECIMAL_PRECISION=3 will output numbers with 3 decimal places(using %lf format). Starting with GDAL 1.11, another option is SIGNIFICANT_DIGITS=3, which will output 3 significant digits (using %g format).

The AIG driver is also available for Arc/Info Binary Grid format.

NOTE: Implemented as gdal/frmts/aaigrid/aaigriddataset.cpp.

Driver capabilities

Supports CreateCopy()

This driver supports the GDALDriver::CreateCopy() operation

Supports Georeferencing

This driver supports georeferencing

Supports VirtualIO

This driver supports virtual I/O operations (/vsimem/, etc.)