ABSTRACT
This chapter presents an approach to the problem of passive localization and tracking of contacts in a multipath environment. For three-dimensional tracking, it is well known in radar-sonar work that serious degradation of elevation or depth measurements is caused by multipath. This happens when the source is at low grazing angles or is within a beam width or so of the bounding surface. Multipath tracking yields contact motion estimates not only in the azimuthal, but also in the vertical plane. The depth parameter provides a clue as to the classification of the source. While strong multipath conditions introduce detrimental modulation to the performance of the bearing tracker, they naturally improve the performance of the time-delay tracker, thus opening a new observation window to the source, at a time most needed. The multipath diversity imparts the needed consistency to the measurement equations at each instant of time.
