Because of its integral functions of pan, tilt and zoom, the PTZ camera has attracted much interest for applications in surveillance and monitoring. In this study, multiple PTZ cameras and the concept of epipolar geometry are used to automatically position and trace the objects in a three-dimensional (3-D) space. The main objective of the study is to extract 3-D trajectories of moving targets in ground space from video data. The proposed method involves four main stages: (1) the collinearity condition is employed to construct the coordinate transformation between the camera and the ground, (2) the moving objects in the camera frames are detected using the progressive background subtraction method, (3) the epipolar geometry and space intersection techniques are used to calculate the ground coordinate of the moving targets, (4) 3-D trajectories of the moving targets can be constructed from their temporal relationship in the image sequence. The proposed system is tested on various scenarios in an open area. The experimental results reveal that the proposed method can successfully track moving targets and present the 3-D trajectories of moving targets in the ground space.