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Top1. Introduction
In the deep-sea environment, surveillance is the most important characteristic of maritime warfare. The Bearings-only target tracking problem is an effective research area for several decades, but now it is extended to bearing and elevation in 3-Dimensionalalthough range measurement is not available. Observer refers to our submarine which is equipped with sonar pick up the radiated noise of target submarine and can generate bearing and elevation measurements of the target. The observer and target submarines both are in deep water doing their surveillance job. The observer can be moving slowly so that it does not radiate much noise, such that self-noise is made less during tracking of the target submarine. Passive mode helps the observer from not being tracked by the target submarine. The aim of the paper is to smooth noisy measurements and also estimate the target motion parameters (TMP) like range, course, and speed, pitch as early as possible. Once the target path is estimated, the weapon can be released on to the target. The basic assumption is the observer and target moves with constant velocity. The state estimation of a non-linear system is extremely difficult. In this research, measurements are linearly not relevant to the target state which makes the entire procedure non-linear. Since bearing and elevation measurements obtained from passive sonar, which makes the process unobservable until the observer performs S-manvuer. Sonar contains a transmitter and receiver which can forward the signal and observes the echoes of the signal is active mode. In this mode there is a chance to observer tracked by the others (Rao, 2006). The scenario consisting of hull-mounted array on the observer, operating in passive mode, is used for tracking the target. As the sonar in a passive mode of operation is considered, there is a low risk of being tracked by others. The fundamental reason for passive mode is to hide the position of an observer and analyze the underwater acoustic waves received from the target (Badriasl & Dogancay, 2014; Blondel, 2010; Mallick, 2013; Richard, 2010).
Hydrophones detect different noises in water in the form of pressures created by the acoustic signals and produce an equivalent voltage as output. Bearing and elevation measurements are obtained by the beam forming technique. Beam forming is the process of listening to or transmitting sound from a sensor at selected angles. It reduces unwanted noise at the processor by amplifying the signals arriving from the selected angle and provides bearing, elevation angles. A horizontal sensor provides the bearing angle and from the vertical sensor obtains the elevation angle (Badriasl & Dogancay, 2014; Blondel, 2010). Three dimensional is a counterpart of 2D. Bearing and elevation measurements are used to track target motion parameters obtain the fast solution when compare to the bearings-only problem.
Figure 1 shows Target tracking in three-dimension plane, the line joining the observer and target is known as line of sight (LOS), the angle between LOS and with respect to reference axis (Y in Figure 1)is bearing angle (B)and the angle between LOS, with respect to reference axis (Z in Figure 1)is Elevation angle (
).
Derived Modified spherical coordinates (MSC)are well appropriate for radar; it required a tracking filter that is non-linear to estimate the location, velocity and acceleration of target in three-dimensional radar(Zhu, 2012) and in earlier research it is implemented in underwater also. Developed the linear Kalman filter into non-linear Kalman filter by escalating nonlinear state equation in Taylor series over the on-going estimating state and developed the linear expressions. Evaluate the different coordinates in 2D bearing-only tracking (BOT) and designed in 3D. Many algorithms for the bearings-only problem are developed (Yang et al., 2003). EKF is applied to bearings-only it linearizes the measurements but EKF doesn’t maintain stability in the solution for highly non-linear systems like 3D.