期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2010
卷号：XXXVIII - Part 7A
页码：88-93
出版社：Copernicus Publications
摘要：Data fusion between aerial photos and LiDAR provides better estimates in forestry and ecological applications, because LiDAR mainly provides the structural information o f objects and aerial photo can add spectral information to them. Without the data fusion, an accurate i dentification of tree crown information from two dimensional data is difficult d ue to shaded and shadow pixels cast on the image and image distortion. Th e aerial photogrammetric techniques cannot reconstruct the objects accurately in three dimensional space s if they are not clearly visible on the photos. The conventional orthophotos, therefore, still have image distor tion due to an inappropriate Digital Su rface Model (DSM) . LiDAR provides a more suit able surface of tree crown structure in three - dimensional space s . This LiDAR - derived DSM could be used in conjunction with conventional photogrammetric techniques to rectify aerial photos and produce true orthop hotos for each image. The existence of different perspective points from the use of multiple images results in different illumination and shadows cast on the DSM from the angle between the sun and the camera . In previous studies, a Z - buffer algorithm was a pplied for the occlusion detection and compensation. However, the technique was computationally intensive. In this study, the camera view and sun - oriented hillshade were generated using the LiDAR - derived DSM. The hillshade surfaces distinguished between th e exposed and the occluded side of the DSM during the composition process of respective true orthophotos. This technique constituted a simpler approach and is applicable to data fusion between LiDAR and multispectral imagery to make an orthographically rec tified image
