Effect of bias on bearing-only target location

The influence of angle measurement bias on passive target location estimation is investigated. First the conditions for target observability are found and generalized to the non-zero-mean measurement noise case. Then the Cramer-Rao lower bound on the estimation error is derived. Numerical examples are included, illustrating the target location uncertainty in the presence of measurement bias     

Nth-order dynamics target observability from anglemeasurements

Necessary and sufficient conditions are presented for the observability of the target's Nth-order dynamics, given direction measurements. The derivations are extremely simple and do not require the examination of an observability matrix or nonlinear differential equations. Previously published observability requirements for the first-order dynamics are shown to be necessary but not sufficient     

Performance analysis of bearing-only target location algorithms

The performance of two well-known bearing-only location techniques, the maximum likelihood (ML) and the Stansfield estimators, is examined. Analytical expressions are obtained for the bias and the covariance matrix of the estimation error, which permit performance comparison for any case of interest. It is shown that the Stansfield algorithm provides biased estimates even for large numbers of measurements, in contrast with the ML method. The RMS error of the Stansfield technique is not necessarily larger than the RMS of the ML technique. However, it is shown that the ML technique is superior to the Stansfield method when the number of measurements is large enough. Simulation results verify the predicted theoretical performance