CALS raster
Contents |
Overview
CALS raster is a group of image file formats associated with the U.S. Department of Defense.
CALS stands for Continuous Acquisition and Life-cycle Support (new name), or Computer Aided Acquisition and Logistics Support (old name).
Format
There are two main formats, and at least 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 Appilcation 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
- Filename extension: .ct3, .nif
- Description: Navy Image File Format (NIFF)
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".
Type 3 files begin with signature bytes 49 49 4E 31 (ASCII "IIN1").
Specifications
- MIL-PRF-28002C: CALS raster; defines Type 1, 3, and 4.
- FIPS PUB 194: Type 2
- MIL-STD-1840C: CALS
