Airborne laser scanning -a new and independent technology in GIS-Photogrammetry

Airborne laser scanning represents a new and independent technology for the highly automated generation of digital terrain models DTM and surface models. Airborne laser scanning development goes back to the 1970s and 1980s, with an early NASA system and other attempts in USA and Canada. Then, the GPS solution of the critical positioning problem made high accuracy performance feasible. Thorough investigations at Stuttgart University from 1988–1993 with a laser profiler proved the high geometric accuracy potential, especially for DTM generation, and clarified the essential system parameters.

The scene was set for the development of genuine Airborne laser scanning systems, which then followed in quick sequence. The method of Airborne laser scanning has successfully established itself within a few years, and quickly spread into various practical applications. In this issue of the ISPRS journal, a number of technical and application papers display the status and performance of airborne laser scanning. Here, in this paper, some additional considerations are submitted on the potential further development and application of the method. Naturally, these will be personal views.
The development of airborne laser scanning has been technology driven. It became initially possible by pulse lasers operating in the near infrared, which gave clearly recordable return signals after diffusion and reflection on the ground. The travel times are recorded to nearly 10y10 s and converted to distance. Recently, also continuous wave  CW. Airborne laser scanning lasers are used, which obtain range by phase measurements. Precise kinematic positioning of the platform by differential GPS and inertial attitude determination by IMU now provide the accurate reference to an external co-ordinate system.

Laser scanning systems furnish geometric results in terms of distance, position, attitude, and coordinates. For each shot, the spatial vector from the laser platform to the point of reflection is established, thus providing the XYZ co-ordinates of the footprint. The overall vertical system accuracy of Airborne laser scanning is usually in the dm order. Most systems presently operate at flying heights of up to about 1000 m above ground. The scan angle is generally -"308, in most cases -"208. Some laser scanning systems provide, in addition to range, information on the intensity of the recorded signal or information range, and in some cases, also amplitude. Airborne laser scanning for multiple echoes within one pulse is latest one.