We present a novel Hough transform method for moving point target detection by using a 4-D parameter space. A new representation, which uses four parameters (the distance variable ρ, the angle variable θ, the velocity variable v , and the distance variable S), is proposed for constant velocity target in the 3-D observation space X-Y-T. By estimating velocity, a target trajectory can be transformed into a 4-D parameter space with a limited range of projection options. Our simulation and analysis show that the new algorithm can produce positive results in suppressing noise points with less computational cost. C 2010 Society of Photo-Optical Instrumentation Engineers.
IntroductionLong-range dim-point target detection is a key technology in many detection systems, and several methods can accomplish moving point target (MPT) detection and trajectory estimation with varying degrees of success. In a remote sensing image, a target is of the size of a pixel or smaller, for the reason that when the gray value of a point target is not the greatest one in the image, it is hard to locate the point target using a single threshold. Generally, the characteristics of motion are used for MPT detection for noise suppression under a low signal-to-noise ratio (SNR) condition. Since the longrange motion is usually continuous and regular in time and space, methods based on the time information are effective ways to solve the problem.In 1977, Falocner 1 used the Hough transform (HT) to detect dim targets by extracting the linear motion trajectory in two-dimensional (2-D) plane. From then on, more and more algorithms based on the HT have been proposed to detect MPT. Some algorithms 1, 2 applied a 2-D HT to find moving targets, since the projection of a constant velocity (CV) point target trajectory to the image plane can be modeled as a straight line in X-Y Cartesian coordinates. But a standard HT 3 will give many false trajectories due to a large search region and too much noise, 4 and the endpoints and connectivity of the target trajectory can not be easily determined or guaranteed, and all that may impact on the track prediction, especially in a limited observing time. Thus, the detection of an MPT is always performed in a three-dimensional (3-D) observation space, which consists of two spatial dimensions and one temporal dimension.The principal problem for 3-D HT is that this approach is impractical because the required storage is too large and the computational time is too long. To overcome this problem, researches have proposed many efficient implementations of the HT.