טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMatan Yeger
SubjectTracking in the Presence of Field-of-View Constraints using
Probabilistic Data Association
DepartmentDepartment of Aerospace Engineering
Supervisor Full Professor Oshman Yaakov


Abstract

Modern tracking systems are required to estimate the distribution of targets in a surveyed scene while coping with a variety of uncertainties, such as unknown number of targets, unknown target

motion models, missed detections and clutter (false measurements). An even more challenging tracking scenario may occur when trying to track targets in a scene with Field-of-View (FOV) constraints. Such situations may arise in urban environments including man-made occlusions (e.g., buildings), or in environments involving topographic constraints (e.g., mountains). In such situations the tracking system needs to reason about information not readily accessible, when the target resides in unobserved regions of the environment.


We address the problem of tracking a single, non-manoeuvring target, moving through a scene containing unobserved regions that are a priori known to the tracker. A modified Probabilistic Data Association (PDA) filter is developed, that can take into account unobserved regions, in addition to target originated measurements, missed detections and clutter. The modification is based on a `negative' information concept, whereby expected but actually missing measurements in a scene containing unobserved regions may be regarded as useful information that can be exploited by the tracking system. In order to use this kind of information it is formulated as a fictitious measurement that embodies the essence of the negative information. The fictitious measurement, and its associated measurement noise covariance, are formulated based on the unobserved region's geometry. This measurement is used to update the target state estimate and error covariance by using a regular Kalman filtering approach within the standard PDA framework.


The performance of the modified PDA filter is studied via numerical simulations. The simulations demonstrate track continuity when the target resides in occluded regions, with a controlled growth of the associated error covariance, thus facilitating robust tracking when the target becomes detectable again. The sensitivity of the proposed approach to mismatched target modeling is discussed and demonstrated via a numerical example. Some suggestions are offered for improving the filter's robustness with respect to mismatched target modeling.