7Roggem M. Airborne laser scanning:clustering in raw data. Interna- tional Arehives of Photogrammetry and Remote Sensing, 2001 ; 34 ( 3/ W4 ) :227-232.
8Masaharu H, Ohtsubo K. A filtering method of airborne laser scanner data for complex terrain. International Archives of Photogrammelry, Remote Sensing and Spatial Information Science, 2002 ; 34 ( 3/B ) : 165-169.
9Zhang K,Chen S,Whitman D,et al. A progressive morphological filter for removing nonground measurements from airborne LiDAR data. IEEE Transactions on Geoscience and Remote Sensing,2003 ;41 (4) : 872-882.
10Chen Q. Filtering airborne laser scanning data with morphological methods. Phologrammetric Engineering and Remote Sensing,2007 ;73 (2):175.