The recently emerged technique of airborne altimetric LiDAR (Light Detection and Ranging) provides accurate topographic data at high speed. This technology offers several advantages over the conventional methods of topographic data collection viz. higher density, higher accuracy, less time for data collection and processing, mostly automatic system, weather and light independence, minimum ground control required, and data being available in digital format right at beginning. Due to these characteristics, LiDAR is complementing conventional techniques in some applications while completely replacing them in several others. Various applications where LiDAR data are being used are flood hazard zoning, improved flood modeling, coastal erosion modeling and monitoring, bathymetry, geomorphology, glacier and avalanche studies, forest biomass mapping and forest DEM (Digital Elevation Model) generation, route/corridor mapping and monitoring, cellular network planning etc. The typical characteristics of LiDAR have also resulted in several applications which were not deemed feasible hitherto with the conventional techniques viz. mapping of transmission lines and adjoining corridor, change detection to assess damages ( e.g. in buildings) after a disaster.
This chapter aims at describing the various aspects of this technology, viz. physical principle, data collection issues, data processing and applications.