- Fundamentals of Object Tracking

Object/target tracking refers to the problem of using sensor measurements to determine the location, path and characteristics of objects of interest. A sensor can be any measuring device, such as radar, sonar, ladar, camera, infrared sensor, microphone, ultrasound or any other sensor that can be used to collect information about objects in the environment. The typical objectives of object tracking are the determination of the number of objects, their identities and their states, such as positions, velocities and in some cases their features. A typical example of object/target tracking is the radar tracking of aircraft. The object tracking problem in this context attempts to determine the number of aircraft in a region under surveillance, their types, such as military, commercial or recreational, their identities, and their speeds and positions, all based on measurements obtained from a radar. There are a number of sources of uncertainty in the object tracking problem that render it a highly non-trivial task. For example, object motion is often subject to random disturbances, objects can go undetected by sensors and the number of objects in the field of view of a sensor can change randomly. The sensor measurements are subject to random noises and the number of measurements received by a sensor from one look to the next can vary and be unpredictable. Objects may be close to each other and the measurements received might not distinguish between these objects. At times, sensors provide data when no object exists in the field of view. As we will see in later chapters of this book, the problems in object tracking can be classified according to the various types of uncertainties involved. In this chapter, we introduce Bayes’ rule, a deceptively simple yet extremely powerful tool from statistical inference, which facilitates recursive reasoning and estimation in the presence of uncertainty. This, in conjuction with the Chapman– Kolmogorov theorem, provides the foundation used to derive the object tracking algorithm presented in this book.