Using Alpha-Beta Trackers in Marine Piloting by Radio Navigation.
Final rept. Jan 79-Jul 80,
COAST GUARD WASHINGTON DC OFFICE OF RESEARCH AND DEVELOPMENT
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Automatic radio aids to navigation for marine usage always employ some sort of smoothing to attenuate noise. As this smoothing period is extended the actual ships motion signal is suppressed along with the noise. When the radio aid is used for positioning in a restricted waterway, such suppression can be undesirable. This work attempts to quantify, through simulation, the tradeoffs in suppressing the noise and affecting the signal. A simple ship model is used to develop a ships maneuvring signal of variable parameters, which is additively combined with simulated noise and processed by the smoothing filter. The latter is an alpha-beta tracker so-called from its radar target history and performance is studied parametric in tracker rise-time. These rise-times should lie between 2.5 and 8 seconds chosen for minimum sensitivity to ship maneuver and ship characteristics. This range accords with current commercial practice in Loran-C receivers signal tracking loops. Gyro compass aiding of the tracker is similarly studied, and shown to offer some advantages in maintaining good performance in the face of these variations, but improving the ability of the tracker to predict future position by a factor of three to five to one. Author