What is Lidar?
Lidar (also called LIDAR, LiDAR, and LADAR) is a surveying method that measures speed or distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used to make digital 3-D representations of the target. The name lidar, now considered an acronym of light detection and ranging (sometimes light imaging, detection, and ranging), was originally a portmanteau of light and radar. Lidar sometimes is called laser scanning and 3-D scanning, with terrestrial, airborne, speed enforcement and mobile applications.
Lidar has a wide range of applications; one use is in traffic enforcement and in particular speed limit enforcement, gradually replacing radar after 2000. Current devices are designed to automate the entire process of speed detection, vehicle identification, driver identification and evidentiary documentation.
Advantages of Lidar over Radar
Radar has wide signal beam divergence, so that an individual vehicle cannot be targeted, requiring significant operator skill, training and certification in order to visually estimate speed so as to locate an offender in a traffic stream, and offenders may use the defence that some other vehicle was offending. Radar will register the speed of any object in its field, for example a tree swaying or an airplane passing overhead.
Lidar has a narrow beam, and easily targets an individual vehicle, thereby eliminating the need for visual estimation, and some models can record an image of the license plate at the same instant as recording the speed violation. Speed estimation takes less than half a second, which, together with the narrow, targeted beam, results in offending vehicles having little warning even when using an evasion device. Lidar can measure the distance between vehicles to detect ‘too close’ (tailgating) infringements.
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