Generally,the land observer platform is stationary，a single stationary observer′s bearings-only tracking (BOT)′s precision is too low and its error is too big.It is impossible to produce a unique track of the target with a completely passive BOT.Whereas this,this paper develops a BOT data fusion method,first develops a solution for the target speeds and heading,after,a BOT,formulated as a least squares (LS) estimator,then produces a unique LS estimate of the target states.The method fuses two sets of bearing readings from visible and infrared sensors,and together with a LRF measurement,produces a unique track.Result from the simulation experiment has corroborated that the method in the data fusion setting has eliminated the bias in the BOT estimator,and it is feasible.