This paper describes a tightly coupled multiple structure adaptive filtering technique that is amenable to real time tracking of a maneuvering target. The procedure provides coherent off-line segmentation of a hemisphere in 3-0 space to yield decision regions, which are then utilized to select an appropriate filter structure. The purpose of using a multiple structure technique is to minimize the computational burden while maintaining tracking accuracy and stability.An important consideration in the evaluation and comparison of real time target tracking techniques is the relative computational requirements of the different procedures [ 1-31. The decoupling technique is an approach that has demonstrated an ability to lessen the computing burden of a tracking procedure [4,5].mically, measurement information is received in spherical coordinates, while a Cartesian-Cartesian model is employed for tracking and estimation. This implies the transformation of a spherical measurement noise covariance matrix to Cartesian form at each sample interval. The decoupling procedure employed involves ignoring some or all of the off-diagonal terms in the Cartesian measurement noise covariance matrix and replacing a three dimensional filter with filters of lower dimensionality. However this procedure is valid only under specific tracking conditions which depend on the target location and the presumed statistical nature of the additive measurement noise.This paper investigates the theoretical restrictions on decoupling and formulates a tracking procedure that enhances the computational efficiency, while maintaining tracking accuracy and stability.l5J.tenne Algarithms . .In this section the algorithms that constitute the multiple structure tracking technique are introduced and their individual requirements are discussed.As mentioned previously the measurements are received in spherical coordinates while a Cartesian-Cartesian model is used for tracking. The state dynamic and measurement equations are given by (1) and (2) respectively.where: x E R" is the state vector, U E R ' is the deterministic input forcing function, z € R"' is the observation vector in Cartesian coordinates ( z is a function of the actual measurements of range, bearing and elevation ), and v E am is a zero mean, white noise process.The measurement noise covariance matrix in Cartesian coordinates can be obtained from the following relationship L where R, = diag. [of, c$, d ] is the spherical noise covariance matrix with , c$ and 2 representing the variances of the range bearing and elevation noise respectively and Fk is the Jacobian of the Cartesian observation vector.The state vector generally has the following form.A linear target motion model operating in a Cartesian coordinate system is inherently decoupled. In addition, the coupling in the observation equation is due to the off-diagonal elements of the noise covariance matrix only. Thus when some or all of the off-diagonal terms of the noise covariance matrix are set to zero, the observation equation is effective...