Recent advances in laser scanning hardware have allowed rapid generation of highresolution digital terrain models (DTMs) for large areas. However, the automatic discrimination of ground and non-ground light detection and ranging (lidar) points in areas covered by densely packed buildings or dense vegetation is difficult. In this paper, we introduce a new hierarchical moving curve-fitting filter algorithm that is designed to automatically and rapidly filter lidar data to permit automatic DTM generation. This algorithm is based on fitting a second-degree polynomial surface using flexible tiles of moving blocks and an adaptive threshold. The initial tile size is determined by the size of the largest building in the study area. Based on an adaptive threshold, non-ground points and ground points are classified and labelled step by step. In addition, we used a multi-scale weighted interpolation method to estimate the bareearth elevation for non-ground points and obtain a recovered terrain model. Our experiments in four study areas showed that the new filtering method can separate ground and non-ground points in both urban areas and those covered by dense vegetation. The filter error ranged from 4.08% to 9.40% for Type I errors, from 2.48% to 7.63% for Type II errors, and from 5.01% to 7.40% for total errors. These errors are lower than those of triangulated irregular network filter algorithms.
Based on the ODMRP(On-Demand Multicast Routing Protocol) in MANET(Mobile Ad hoc NETwork), a reliable ODMRP(R-ODMRP) is proposed for preferable throughput and especially suited for high-speed MANET, which includes packet acknowledgement, lost packet recovery, secure authentication and QoS based packet delivery. With the exploration of active network, R-ODMRP constructs the multicast routing based on the cluster, establishes a distributed mechanism of the acknowledgment and recovery of packet delivery. Along with cluster key distributed in one cluster, this protocol can authenticate the consistency of multicast source and receivers depending on local security strategy. The specific mesh links are adaptively chosen by virtue of the descriptive QoS vectors
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