Manual

June 2004 Isis® Sonar User's Manual, Volume 2
23
Appendix B Isis BAC and GAC File Formats
Isis supports a number of file formats: Q-MIPS, BAC, GAC, and XTF. Each has
distinct advantages. This appendix explains the BAC and GAC formats.
B.1 BAC File Format
You can create a BAC file from transducer beam patterns, or Q-MIPS or Isis can
create it by using theoretical or empirical beam patterns. Although these files
generally have the BAC (Beam Angle Compensation) extension, they reflect the
measured or inferred beam
pattern of the sonar rather than the compensation
that will be applied. In this way, Q-MIPS and Isis need not be concerned with the
origin of a BAC that is applied.
All BAC files are ASCII and consist of paired signal intensity values in decibels
for each degree off vertical. A sample beam pattern (
SM28.BAC) file is shown in
Figure B-1.
/* Beam patterns in dB (angle off vertical, port, starboard)
*/
22.183 21.703 /* (Max level bias in dB, port &
starboard) */
131 /* number of angle bins */
012.858 12.166 /* angle off vertical, port (dB),
starboard (dB) */
112.858 12.166
212.858 12.166
312.858 12.166
412.858 12.166
...
...
...
1290.552 0.599
1300.000 0.000 /* angle off vertical, port (dB),
starboard (dB) */
Figure B-1. Sample BAC beam pattern file
Appendix B: Isis BAC and GAC File Formats