FilteringAirborneLaserScanningDatawithMorphologicalMethods.pdfVIP

Filtering Airborne Laser Scanning Data with Morphological Methods Qi Chen, Peng Gong, Dennis Baldocchi, and Gengxin Xie Abstract Filtering methods based on morphological operations have been developed in some previous studies. The biggest challenge for these methods is how to keep the terrain features unchanged while using large window sizes for the morphological opening. Zhang et al. (2003) tried to achieve this goal, but their method required the assumption that the slope is constant. This paper presents a new method to achieve this goal without such restrictions, and methods for filling missing data and removing outliers are proposed. The experimental test results using the ISPRS Commission III/WG3 dataset show that this method performs well for most sites, except those with missing data due to the lack of overlap between swaths. This method also shows encouraging results for laser data with low pulse density. Introduction Airborne laser scanning (ALS) is gaining popularity in various environmental applications, ranging from DEM mapping, transportation, and urban studies to forest management, hydrology, and ecology (Flood and Gutelius, 1997; Chen et al., 2006). Compared with digital photogrammetry (Gong et al., 2000; Sheng et al., 2001; Gong et al., 2002) and radar interferometry (Hoekman and Varekamp, 1998), laser altimetry has the advantage of recording the elevation of earth surface directly. Nevertheless, there is a great need for efficient data processing methods (Axelsson, 1999). In particular, filtering, the abstraction of bare earth from ALS points, is a crucial procedure for ALS data processing (Sithole and Vosselman, 2004). It, with quality control, generally consumes an estimated 60 to 80 percent of processing time (Flood, 2001). However, the details of filtering Qi Chen is with the Center for the Assessment and Monitoring of Forest and Environmental Resources CAMFER), University of California at Berkeley, Berkeley, CA 94720 (qch@). Peng Gong is with t