19 June 2001




P. Wischow    M. Lohrenz
Naval Research Laboratory
Stennis Space Center, MS 39529-5004



The Compressed Aeronautical Chart (CAC) database is a global library of compressed, scanned, aeronautical charts that support Navy and Marine Corps aircraft moving-map displays and mission planning systems. The source for the CAC library is the National Imagery and Mapping Agency (NIMA) standard ARC (equal Arc-second Raster Chart) Digitized Raster Graphics (ADRG) image data set. ADRG is compressed and transformed into CAC via vector quantization and color compression techniques. The Map Data Formatting Facility (MDFF) of the Naval Research Laboratory, Stennis Space Center, MS (NRLSSC), produced the CAC library from April, 1989, until September, 1995, when NRLSSC transitioned the CAC Production System to NIMA.

NIMA distributes CAC installments on Compact Disk Read-Only Memory (CDROM).

Each CDROM contains data at one of seven available chart scales, from 1 :5M (M=million) to 1:50k (k=thousand).

CAC data is structured according to the Tessellated Spheroid (TS) map projection system. TS divides the world into five zones (table 2). Each zone is divided into rows and columns of segments, and each segment represents approximately 2 in. x 2 in. of paper chart. The geographic coverage of a segment is dependent on the chart scale and the zone in which the segment is located. The reader is advised to become familiar with these reports prior to using the CAC Access Software.

This report is a programmer's reference for accessing the CAC library via NRL-developed CAC Access Software, which is a user-callable suite of utility programs. The CAC Access Software was written in ANSI C and is currently running under the following operating systems: OpenVMS, Unix, MS-DOS, Windows 3.1, Windows 95 and Macintosh.

Sponsored by the National Imagery and Mapping Agency.

Published in July 24, 1998.
Naval Research Laboratory Contribution Number NRL/MR/7441-97-8073.
NRL Memorandum Report