ABSTRACT
Aerial photogrammetry and airborne laser scanning (ALS) are the two most widely used methods for generating digital elevation models, including digital terrain models that depict ground topography and digital surface models that depict the height of the ground, structures, and vegetation cover. In contrast to large-footprint systems, small-footprint ALS systems illuminate only one or a few surfaces within the footprint, yielding waveforms with distinct return pulses corresponding to specific surfaces. Conventional pulsed laser scanner systems for topographic mapping are based on time-of-flight ranging techniques to determine the range to the illuminated object. Concerning modulation techniques, laser systems can be divided into two groups: continuous wave and pulsed lasers. Analysis of a received waveform in order to extract the attributes of illuminated surface is a difficult task because different processes impact the shape of the waveform. The waveform has to be captured with a high bandwidth receiver and with an adequate sampling rate of the analog-to-digital converter.
