IBM Technical Disclosure Bulletin (TDB v36 n12 12-93 p101-104)
English (United States)
4 pages / 154.2 KB
Enhancement of Passive Sonar Gram Data Using Image Processing and Monochrome
passive sonar systems employ CRT B-scan presentations of
sonar gram data. Older systems presented this information on paper
rather than on a CRT. Experienced operators of older systems were
able to review these paper presentations and find weak targets often
missed by novice operators. This material describes an algorithm and
implementation to duplicate the performance of the experienced
operator and a paper gram with a novice operator on a modern system
using a CRT display. Another enhancement is illustrated; rate
filtering of the B-scan presentations; a process not possible with a
experienced sonar operators have been able to detect
the presence of weak passive sonar signals recorded on paper sonar
gram displays by tilting the recording so that the time history of
the dots comprising the target is foreshortened and by rotating the
paper so that the time history of the dots for a single target is
along the line of sight. This is the so called visual or "eyeball"
integration technique. In modern sonars using digital image
processing, sonar gram displays employ a small finite number of fixed
integration intervals. The output of each integration produces a
gram line of display data presented in a "waterfalling" format on a
CRT to aid in operator recognition contacts. This corresponds to the
tilting of the paper gram at fixed angles and does not allow any
reorientation of the line of sight along the target rate. Physically
rotating the CRT monitor with 3 degrees of freedom is awkward.
Having the operator stand and move his head about the CRT is also
impractical. The method described here performs the visual
integration done with the paper gram in real time and under operator
control, using the architecture and algorithm described herein.
technique, employed by a novice operator using a CRT gram
display, matches the performance of paper gram display in the hands
of an experienced operator. The implementation employs a simple
two-dimensional image processing algorithm which is implemented in
real time and is under operator control. This implementation employs
windowing to maintain the appearance of the original CRT
presentation, enabling a novice operator to employ the technique
without retaining. It should also reduce operator search time. A
typical passive sonar produces signal-to-noise outputs, luminescence
levels at many frequencies, narrowband, or at many bearing,
broadband, as a function of time. This data is time averaged at each
frequency or bearing, requantized to a luminescence level and
presented to an operator as a line or row of dots across a CRT.
Successive outputs in time are drawn, stacked one upon the other,
producing a "waterfalling" display format with the newest data on top
and the oldest at the bottom. Integration or averaging times per
scan line employe...
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