| Composed of laser range finder, global positioning system and inertial navigation system and as a relatively new remote sensing technology, Airborne Laser Scanning has become a desired tool to quickly collect radiometric and geographic information of all kinds of ground objects with high precision and high point density. On the basis of classification and building reconstruction,3D coordinate information is extracted from the geographic information. This technique has wide applications in the fields of fundamental measuring, DEM, DOM, DLG production,3-dimentional digital city and so on.The post-processing software we have in our company, coming with the Airborne Laser System (ALS), which is like a black box, can't meet all the practical requirements, and at the same time, the foreign seller of this software keeps it as a secret. There are no such functions as reading and format converting of raw lidar data in the software. On the support of a special task in our company, the software of Airborne Laser System (ALS) is developed for meet the practical requirements.Standard LAS format LiDAR data are used in this dissertation to be read into files, converted, and then filtered using the intensity information for the first time and using the angle limitation and window-moving algorithms for the second time, and then processed to do the ground points extraction as results in the practical engineering projects, and at last, the curving surface fitting method of discontinuous ground points based Least Square Match was studied. The author use computer language to fulfill the algorithm and use different parameters to compare and analyze the final results separately. This algorithm is approved that it runs faster with high precision and can meet the data procession requirements in different conditions when extracting ground points, and it can be seen that the multiple power equation obtained by the curving surface fitting method can depict the ground surface model precisely. |
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