An FPGA-based vehicle speed measurement system using an uncalibrated camera

Measuring a vehicle´s speed using a video image is an important technique in an intelligent transportation system. This paper presents a hardware implemented vehicle speed measurement (VSM) system. The operation of the system consists of three steps. First, we remove vehicles from a series of captured images to create a background. To do this, we introduce a simplified exclusion algorithm optimized to the hardware. Second, we subtract the background from the incoming image and concurrently apply affine rectification. Finally, based on the rectified image, we track the vehicles and measure the velocity. The system uses two SRAMs and one FIFO to store images. At each step, we present a memory management method of two SRAMs to store multiple images in one SRAM. This enables our system to obtain two images in a single full memory scan. Our system obtained ± 7.5% velocity error using an experiment comparing the vehicle´s speedometer and the vision-based measured velocity.