Urban object classification of multispectral airborne LiDAR data with multidimensional Gauss mixture model and neighborhood constraints
WANG Liying, WU Ji, YOU Ze, LI Yu, CAMARA Mahamadou
2023, 52(3):
419-431.
doi:10.11947/j.AGCS.2023.20210153
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Making full use of the spatial location and multispectral information of multispectral airborne LiDAR point cloud to completely and accurately segment objects is an important prerequisite for the subsequent application of the data.However, the traditional point-based classification algorithms are difficult to design and inefficient to execute due to the limitations of point cloud that cannot clearly represent topology and neighborhood information.Moreover, the classification algorithms which interpolate point cloud into image is limited by the information and precision loss of image, which leads to low classification accuracy. In addition, neither point cloud nor image can directly represent the three-dimensional geometry of objects, which is not conducive to the subsequent three-dimensional modeling and analysis of objects.Therefore, this paper proposes a classification algorithm based on multi-dimensional Gauss mixture model (GMM) and neighborhood constraints for multispectral airborne LiDAR data. The multispectral airborne LiDAR data are firstly voxelized into a multi-valued virtual voxel structure based on the principle of no information loss and representing neighborhood information explicitly, in which the virtual voxel is the combination of the voxel and its internal laser points, and the virtual voxel value is a feature vector composed of the spectrum, elevation, local normal vector distribution and point density features of the laser points in the voxel.Then, a fuzzy clustering segmentation model is constructed to segment the virtual voxel structure, and the fuzzy membership matrix of each virtual voxel is obtained.Among them, the multi-peak distribution of objects in feature space is fitted by multi-dimensional GMM to establish the label field, and the probability distribution of multi-dimensional GMM is used as the dissimilarity metric.The spatial correlation of classes for the adjacent voxels in the label field is modeled by the hidden Markov random field (HMARF) model, and the prior probability under the neighborhood constraint is established, which is used as the parameter to control the clustering scale.An objective function with a regularization term is used to solve the scaling sensitivity problem of clustering.Finally, the membership matrix is defuzzified to determine the classification result.The effectiveness and feasibility of the proposed algorithm are quantitatively evaluated based on Optech Titan multispectral airborne LiDAR data of different complexity and different data volume.The experimental results show that the average overall accuracy and Kappa coefficient of the algorithm is 91.32% and 0.872, respectively, which can effectively realize the classification of various urban objects.The proposed algorithm makes comprehensive use of the spectral, geometric and neighborhood consistency information of objects, expands the types of information utilization, and provides a feasible scheme for the comprehensive utilization of the spatial location and multispectral information of multispectral airborne LiDAR data.
