Forest Characteristics and Effects on LiDAR Waveforms Modeling and Simulation

LiDAR (Light Detection And Ranging) remote sensing has been used to extract surface information as it can acquire highly accurate object shape characteristics using geo-registered 3D-points, and therefore, proven to be satisfactory for many applications, such as high-resolution elevation model generation, 3-D city mapping, vegetation structure estimation, etc. Large footprint LiDAR especially, offers the great potential for effectively measuring tree parameters in forested areas. Based on the radiative transmission function for vegetation structure, a simplified model cited from previous paper was used to simulate how the vegetation parameters and slope degree affect LiDAR waveform characteristics. And an extinction coefficient is introduced to the model due to the influence of dense vegetation canopy and the simplified and ideal model. The experiment results show that vegetation canopy, trees distribution in one footprint and terrain slope influence LiDAR waveform shapes, while tree height just affects the starting position of the waveform. The model with the extinction coefficient explains that vegetation canopy can weaken laser which makes the return echo weaker in lower canopy. Although based on some assumptions, simple and ideal conditions, the above results obtained from GLAS data are suitable for other LiDAR systems and have great significance to LiDAR applications in forest parameters extraction, especially in sloped areas, it is necessary to correct terrain effects when deriving vegetation height from LiDAR returns. As a matter of fact, the model has to be perfected in later work so as to be more practical.