Dataset File Formats
Different types of datasets are stored in a number of different formats.
In general, datasets are stored in the format in which they were created
or acquired, using compression when appropriate. When it is expected
that a dataset will be extensively used in another format or may be
needed by users with limited access to software for converting between
formats, the dataset may be stored in more than one format.
Some GIS and image processing software, such as Arc/Info and LAS, use
multiple files or directories to store a single dataset. In such cases,
it it recommended that the tools of the particular software package be
copy multifile datasets.
Most GIS and image processing software packages provide support for converting between file formats.
The dataset format can usually be identified by the directory name or
file extension. The file types can be roughly classified as follows:
- Band-interleaved-by-line: data are stored in
the order (line 1, band 1), (line 1, band 2),
..., (line 1, band N), (line2, band 1), (line 2,
band 2), ... .
- Band sequential: data are stored in the order
(line 1, band 1), (line 2, band 1), ... (line M,
band 1), (line 1, band 2), (line 2, band 2), ...
(line M, band 2), ... .
Attention PC users: 16-bit integer and 32-bit
floating-point data are in "big-endian" format; i.e., the most
significant byte comes first.
A subroutine to facilitate reading and unpacking "flat" binary files in
band-sequential (BSQ) format is available in both Fortran 77
and C-language versions.
MacIntosh Users can use Photoshop to ingest 16-bit .bsq
data. After uncompressing the file, open it as a "raw" file (make sure
you can Open All Documents). In the ensuing dialog box, enter the image
width and height (from the documentation page for the dataset) and enter
the number of bands as the "Channel count". The depth is 16 bits, byte
order is "Mac", and header size is 0.
- Files compressed using the GNU gzip utility.
Usually appended to another file extension.
- Files compressed using Unix "compress" utility.
- General descriptive text
- Tables in ASCII format
- (no file extension) Arc/Info directory, under
which INFO tables are maintained.
- (no file extension) Arc/Info data directory,
containing data files for a grid or coverage.
- Arc/Info EXPORT format.
- ERDAS-7.X format single-band file.
- ERDAS-7.X format multi-band file.
- Data descriptor record: projection and
georeferencing information. A program for
printing DDR contents is available in both C-language
source code and MSDOS
- Processing history file.
- Image data, compressed (using LAS-specific
algorithm) or uncompressed. Uncompressed
version is identical to .bsq file.
- Digital elevation model data. NOTE: some
software may require that these files be
reblocked before use. A program to read a
DEM file and convert it to a 16-bit binary array
is available in both C-language
source code and MSDOS
Last change: 2004 Dec. 1,
R. A. White / firstname.lastname@example.org