Moving object detection is an important part of computer vision system, especially in transportation systems. Moving object detection has been widely investigated and many algorithms have been proposed in the literature. However, moving object detection becomes more challenging when the image sequence is captured by moving camera. In this case, not only real moving objects but also static objects can be regarded as moving objects. Therefore, it is difficult to identify real moving objects in this situation. This book would show the readers how to tackle this problem, by using an optical flow method.