1. LiDar
Lidar, which stands for Light Detection and Ranging, is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth. These light pulses—combined with other data recorded by the airborne system — generate precise, three-dimensional information about the shape of the Earth and its surface characteristics.
A lidar instrument principally consists of a laser, a scanner, and a specialized GPS receiver. Airplanes and helicopters are the most commonly used platforms for acquiring lidar data over broad areas. Two types of lidar are topographic and bathymetric. Topographic lidar typically uses a near-infrared laser to map the land, while bathymetric lidar uses water-penetrating green light to also measure seafloor and riverbed elevations.
2. Mobile Maping
Mobile mapping technology (MMT) involves the dynamic digitization at very high spatial resolution of complex environments (mainly urban environments) using a mobile terrestrial platform. The aim is to acquire very precise and very accurate georeferenced data of objects of interest as well as in fine data for applications which require this level of geometric precision (3D city modeling, pedestrian and vehicle detection for autonomous navigation, digitizing roadway property, archaeological excavations, etc.). This chapter will focus on mobile mapping from roads, but similar methods have also been developed for digitizing rail networks through the use of trains equipped with similar sensors.
