In this paper the principle of triangulation is used as a basic method for range estimation. However, when the target directions are nearly collinear relative to the baseline the ratio of IR energy absorbed at the end of a baseline has to be introduced in a measurement vector to obtain acceptable results. In that case, a recursive estimator for the extinction
coefficient that describes the influence of the atmosphere also must be applied. Both methods are implemented within the extended Kalman filter type target state estimator. The results obtained by simulations and experimental data processing show the advantages but also the disadvantages caused by saturation effect when the target is close enough to one of the
sensors. The appropriate hybrid approach in application of algorithms, triangulation and proposed method with extended measurement vector, is suggested as a solution.