CALS raster

File Format
Name	CALS raster
Ontology	Electronic File Formats Graphics CALS raster
Extension(s)	.ct1, .cal, .ras, .ct2, .ct3, .nif, .ct4, .c4
PRONOM	x-fmt/28
Released	≤1990

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).

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

Software

• ImageMagick
• Konvertor
• XnView

Sample files

• dexvert samples — image/cals

Resources

• Tiled Raster Graphics and MIL-R-28002A: A Tutorial and Implementation Guide (Type 1 and 2)
• CALS Raster File Format Summary, from the Encyclopedia of Graphics File Formats
• Wikipedia article