In bearings-only target motion analysis (BOTMA), the common hypothesis is that the observer maneuvers while the source is traveling according to a constant speed and course. But there is no reason that the roles of each protagonist be not exchanged. In this paper, we consider an uncommon scenario: the trajectory of the target is composed of two legs (i.e. a target brutally changes its heading while keeping its speed) and the observer does not maneuver. We prove that the trajectory of the target is observable under non-restrictive conditions. A batch estimator is proposed and its performance is compared with the classic Cramèr-Rao lower bound (CRLB). Monte-Carlo simulations reveal the efficiency of the estimator. The robustness to a non brutal heading change is evaluated. Then an ad-hoc estimate taking the correct model into account isproposed and applied to simulated data. Again, its performance is compared to the CRLB and its robustness is evaluated when the speed of the target changes. Finally, the respective performances of the TMA made by each mobile are compared.

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