NITF -- National Imagery Transmission Format
GDAL supports reading of several subtypes of NITF image files, and writing
simple uncompressed NITF 2.1 files. NITF 1.1, NITF 2.0 and NITF 2.1
files with uncomprssed or VQ compressed images should be readable.
JPEG2000 compressed images are also supported, but only if GDAL also has
the JP2KAK driver enabled. Other compression mechanisms are not supported
at this time. The read support test has been tested on CIB and CADRG RPF
products.
NITF files can contain several images as well as other layers such as
graphics (CGM) and text. Currently GDAL will only read the first image. All
other images and auxilary information are ignored.
Color tables for pseudocolored images are read. In some cases nodata values
may be identified. Lat/Long extents are read from the IGEOLO information in
the image header if available. Other coordinates systems (such as MGRS) are
ignored at this time. If high precision lat/long georeferencing information
is available in RPF auxilary data it will be used in preference to the low
precision IGEOLO information. In theory all input pixel types except 1bit are
supported, but only 8bit types have actually been tested.
Most file header and image header fields are returned as dataset level
metadata.
Creation Issues
On export NITF files are always written as NITF 2.1 with one uncompressed image
and no other auxilary layers. Georeferencing can only be written for
images using a geographic coordinate system. Coordinates are implicitly
treated as WGS84 even if they are actually in a different geographic coordinate
system. Pseudo-color tables may be written for 8bit images.
In addition to the export oriented CreateCopy() API, it is also possible to
create a blank NITF file using Create() and write imagery on demand. However,
using this methology writing of pseudocolor tables and georeferencing is
not supported unless appropriate IREP and ICORDS creation options are supplied.
Creation Options:
- Most file header, and imagery header metadata and security fields can
be set with appropriate creation options. For instance setting
"FTITLE=Image of abandoned missle silo south west of Karsk" in the
creation option list would result in setting of the FTITLE field in the NITF
file header. Use the official field names from the NITF specification
document.
- ICORDS: Set to "G" to ensure that space will be reserved for
geographic corner coordinates to be set later via SetGeoTransform(). (Only
needed for Create() method, not CopyCreate()).
- IREP: Set to "RGB/LUT" to reserve space for a color table for
each output band. (Only needed for
Create() method, not CopyCreate()).
- LUT_SIZE: Set to control the size of pseudocolor tables for
RGB/LUT bands. A value of 256 assumed if not present. (Only needed for
Create() method, not CopyCreate()).
- TFW=YES: Force the generation of an associated ESRI world
file (.tfw).
- BLOCKXSIZE=n: Set the block width.
- BLOCKYSIZE=n: Set the block height.
Credit
The author wishes to thank AUG
Signals and the GeoConnections
program for supporting development of this driver.
See Also: