Two-step modeling and observability for bearings-only tracking

Conventional models for bearings-only tracking (BOT) are to jointly solve target motion parameters and algorithms are complex. In this paper a two-step model is established for BOT and a sequential algorithm for solving target motion parameter is proposed, in which distances, velocities and courses of targets are solved respectively, i.e., distances are geometrically solved by means of supposed bearings, then velocities and courses can be obtained in terms of the solved distances. Observability of BOT is analyzed and a sufficient and necessary condition of observability is obtained for given observer maneuver. The sequential algorithm can solve target distances quickly and meet the requirement of fast solution.