Showing papers by "Melvin J. Hinich published in 1980"

Passive target location using bearings from a platform whose track is uncertain (Corresp.)

Abstract: Suppose that a moving platform measmw the relative bearings of a number of distant targets. If the platform track is precisely known and the targets are stationary, then two sucsessive bearings are sufficient to identify the location of a given target using triangulation. As there is always some error in the bearing estimates, additional bearings are needed to obtain a more accurate estimate of each target's location. If the position of the platform is ancertaiq then the target location problem is more complicated. Simple ad hoc estimators of target coordinates when there are significant random errors in the measurem ent of the platform track are presented. The only assumption made about the platform track is that it is distant from the targets.

Beamforming when the sound velocity is not precisely known

Abstract: Beamforming is an integral part of most signal processing systems in active or passive sonars. The delays used to generate a beam are functions of the sound velocity, which depends on temperature, salinity, and pressure. There is a loss in array gain if the delays are incorrectly set. This will occur when the sound velocity in the water surrounding the hydrophones is different from the velocity that was used to set the delays. This paper makes two points: (1) fixed delay line sonars suffer a loss in gain when the true sound speed in the water is different from the velocity that is used to set the delays, and (2) there are signal processing techniques for two‐ or three‐dimensional arrays that yield source bearings that are independent of the true sound velocity. These techniques require variable time delays, which can be realized using digital processing.