The Theory of SCREEN

This report documents the theory which underlies the SCREEN program, a computer program designed to evaluate acoustic detection and localization performance of an anti-submarine protective force about a Naval task force or other shipping. A companion user's manual for SCREEN supplements this report. The measures used to evaluate the SCREEN performance are: cumulative detection probability against specific target approach tracks and cumulative localization performance against these same tracks. In addition to cumulative measures, 'snapshot' detection and localization measures are also computed, which provide an indication of the detection and localization coverage of the defensive screen at a specified time. The SCREEN program operates on data files which contain moderately detailed descriptions of the acoustic environment (propagation, noise, etc.), the sensor parameters and tactics, and the screen penetrator (target) parameters and tactics. These descriptions include both deterministic and stochastic parameters. The data file contents can be created, altered, and displayed by the user under program control. Once the data files have been created, subsequent use of SCREEN is straightforward and concise, involving user-selectable program options and machine prompts for input. The underlying detection process is a modified (lambda, sigma)-jump process. The target process is a modified Integrated Ornstein-Uhlenbeck (IOU) process. The basic localization algorithm is an 'Information Flow' Kalman filter. Bayesian updating techniques are used to evaluate search effort, along lines similar to techniques found in computer assisted search programs which are currently being implemented in the Fleet.