Laser scanning systems are based on laser ranging, which measures the distance between a sensor and a target using the elapsed time between the emission of an infrared pulse and the detection of a reflected return. Extant literature classified laser scanning systems as either discrete return or full-waveform recording.Discrete laser scanning systems record single or multiple returns from a given laser pulse. By contrast, full-waveform laser scanning systems record the entire reflected energy from a return, thereby resulting in complete sub-meter vertical profiles of a target. From the perspective of geometric road modeling, discrete return laser scanning systems are usually preferred because laser pulses cannot penetrate road surfaces to record the complete vertical profile of the target. Another type of classification for laser scanning systems is based on the type of platform. Based on the platform type, the following three types of laser scanning systems are classified: an airborne laser scanning system, a mobile laser scanning system, and a terrestrial laser scanning system. The following sections describe each of these systems in detail.
