CALS raster
CALS raster is a collection of image file formats developed by the U.S. Department of Defense as part of the CALS initiative.
CALS stands for Continuous Acquisition and Life-cycle Support (new name), or Computer Aided Acquisition and Logistics Support (old name).
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Format
There are two main formats (Type 1 and Type 2), and two more that have also been placed under the CALS umbrella.
Type 1
- Filename extension: .ct1 (MIL-PRF-28002C), .cal (MIL-PRF-28002B)
Type 1 files have a 2048-byte ASCII header, consisting of up to 16 128-byte header fields.
Bi-level image data follows, which always uses CCITT Group 4 compression.
There are two versions of Type 1 format: one defined in MIL-PRF-28002B, and one defined in MIL-PRF-28002C.
Type 2
- Description: Office Document Architecture (ODA) Raster Document Application Profile (DAP)
- Filename extension: .ct2
Type 2 is a more complex format, which adds support for multiple images, uncompressed images, and other things.
Type 3
- Description: Navy Image File Format (NIFF)
- Filename extension: .ct3, .nif
Refer to NIFF (Navy Image File Format).
Type 4
- Description: JEDMICS C4
- Filename extension: .ct4, .c4
Refer to JEDMICS C4.
Identification
Type 1 files most likely begin with ASCII string "srcdocid:", "rorient:", or "version: MIL-STD-1840".
Specifications
- MIL-PRF-28002C: CALS raster; defines Type 1, 3, and 4.
- FIPS PUB 194: Type 2
- MIL-STD-1840C: CALS
