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--- radar:tws [2018/06/08 10:06] – george
+++ radar:tws [2026/04/28 18:24] (current) – mauro
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->TOC ok for now! Please use headers instead of bold!  --- //[[webmaster@localhost|DokuWiki Administrator]] 2018/04/24 16:18//
 ===== TWS =====
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 too slow to be used in a system where speed of operation is one of the primary goals.
-In principle, a track can be initiated from the target location information obtained on two successive scans of the radar antenna. In practice, however target information from three or more scans is usually needed to intiate a track.Two scans would be adequatewhen there is only one or a few aircraft within view, but when the radar has in view  a larger number of echoes, one or more additional scan may be needed to prevent false tracks from being initiated. Thus it is more usual to require three or more scan before establishing a track.A clutter map is used to store, the locations of fixed clutter echoes and prevent tracks from being initiated based on a clutter echo combined with a real target detection.Such tracks can eventually be recognized as false  and can be dropped , but it takes time and computer capacity to do so when there are a large number of them.Clutter echoes for inclusion in the clutter map are those echoes that do not change their location with time or that change loction too slowly to be targets of interest.
+In principle, a track can be initiated from the target location information obtained on two successive scans of the radar antenna. In practice, however target information from three or more scans is usually needed to intiate a track.Two scans would be adequate when there is only one or a few aircraft within view, but when the radar has in view  a larger number of echoes, one or more additional scan may be needed to prevent false tracks from being initiated. Thus it is more usual to require three or more scan before establishing a track.A clutter map is used to store, the locations of fixed clutter echoes and prevent tracks from being initiated based on a clutter echo combined with a real target detection.Such tracks can eventually be recognized as false  and can be dropped , but it takes time and computer capacity to do so when there are a large number of them.Clutter echoes for inclusion in the clutter map are those echoes that do not change their location with time or that change loction too slowly to be targets of interest.
-The process of initiating a track in a dense environment of targets and clutter not diminated by the radar can be quite demanding in both computer software and hardware. Initiation of a new track may take more computer time  and capability than any other aspect of ADT.Requiring three scans for a civil air-traffic control radar to establish a track is usually not a burden. Wiating three scans for track establishment , however may be an excessively long time for a military  air-defense radar that has to direct weapon-control radars to defined against high speed trackers that "pop up" at short range over the horizon.it is possible to quickly aquire  the target on the basis of a sinlge scan past the target if the radar can obtain a quick second look. This might be done with a look-back beam directed to the angle of the original detection.The quick look-back can provide confirmation of detection  and an estimate of target's related velocity. A phased array radar is well suited for this purpose, but mechanical rotating radar can also be outfitted with a fixed look back beam. Look back might also be accomplished with a 3D radar whose eletronically scanning beam in elevation is returned to the elevation angle of initial detection, before the radar beam entirely scans past the target.
+The process of initiating a track in a dense environment of targets and clutter not diminated by the radar can be quite demanding in both computer software and hardware. Initiation of a new track may take more computer time  and capability than any other aspect of ADT.Requiring three scans for a civil air-traffic control radar to establish a track is usually not a burden. Waiting three scans for track establishment , however may be an excessively long time for a military  air-defense radar that has to direct weapon-control radars to defined against high speed trackers that "pop up" at short range over the horizon.it is possible to quickly aquire  the target on the basis of a sinlge scan past the target if the radar can obtain a quick second look. This might be done with a look-back beam directed to the angle of the original detection.The quick look-back can provide confirmation of detection  and an estimate of target's related velocity. A phased array radar is well suited for this purpose, but mechanical rotating radar can also be outfitted with a fixed look back beam. Look back might also be accomplished with a 3D radar whose eletronically scanning beam in elevation is returned to the elevation angle of initial detection, before the radar beam entirely scans past the target.
 === Generation of tracking "gates" ===
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 mean square error in the smoothed position and velocity.
-When the Kalman filter is modeled with the target trajectory as a straight line , and the measurement noise and the trajectory disturbance are modeled as white , guassian noise with zero mean , the kalamn filter equations reduce to the α - β tracker equations with  α and  β computed sequentially by the kalman filter procedure.Blackman states that " Experience with airborne radars has shown the versatility of kalman filter to be almost indespensable when dealing with problems presented by missing data and variable measurement noise statics" . The kalman filter has better performance than the  α - β tracker since it utilizes more information. The  α - β tracker, however might be considered when the target's maneuver statistics are not known or in a dense target environment where computational simplicity is important. The Kalman filterand the  α - β tracker also can be applied to control digitally the feedback loop in the single target tracker. The Kalman filter is essentially a set of mathematical equations that implement a
+When the Kalman filter is modeled with the target trajectory as a straight line , and the measurement noise and the trajectory disturbance are modeled as white , guassian noise with zero mean , the kalamn filter equations reduce to the α - β tracker equations with  α and  β computed sequentially by the kalman filter procedure.Blackman states that " Experience with airborne radars has shown the versatility of kalman filter to be almost indespensable when dealing with problems presented by missing data and variable measurement noise statics" . The kalman filter has better performance than the  α - β tracker since it utilizes more information. The  α - β tracker, however might be considered when the target's maneuver statistics are not known or in a dense target environment where computational simplicity is important. The Kalman filter and the  α - β tracker also can be applied to control digitally the feedback loop in the single target tracker. The Kalman filter is essentially a set of mathematical equations that implement a
 predictor-corrector type estimator that is optimal in the sense that it minimizes the
 estimated error covariance—when some presumed conditions are met. Since the time of