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遥感点云隐特征相似度驱动的两阶段单木分割网络

A Latent Feature Similarity Driven Two-Stage Individual Tree Segmentation Network for Remote Sensing Point Clouds

  • 摘要: 针对传统的遥感点云单木分割方法在处理大规模点云数据时, 数据噪声、数据异常、密集树冠、树木遮挡等挑战导致分割结果准确性不高的问题, 结合PointNet++和卷积神经网络, 提出一种点云隐特征相似度驱动的两阶段单木分割网络, 以端到端的方式实现遥感点云数据单木分割. 在预分割阶段, 首先通过点云数据分层次处理提取输入场景点云的局部和全局特征, 构造点云数据隐特征矩阵; 然后通过2个网络分支分别生成相似度矩阵和置信度图, 相似度矩阵用于衡量每对采样点之间的相似度, 并将具有高相似度的采样点判定为同一个实例形成一个预测分组, 置信度图则反映每个实例预测的可信程度, 并过滤低置信度的预测分组确保分割结果的可靠性和准确性. 为了进一步提升单木分割的准确率, 在细分割阶段引入点云自适应KNN(A-KNN)扩散模块, 通过平滑单木预分割结果减少遥感点云孤立点的自动分割误判. 实验结果表明, 所提网络充分利用点云数据的空间信息和局部特征, 借助A-KNN扩散大幅度提升遥感点云单木分割的准确率和鲁棒性; 在标注数据集上, 该网络单木分割的平均准确率为96.33%, 平均交并比为0.9206.

     

    Abstract: Aiming at the inaccurate and inefficient results of traditional individual tree segmentation approaches for large-scale remote sensing point cloud data due to the challenges of data noise, data anomalies, dense canopy, tree occlusion, etc., a latent feature similarity driven two-stage individual tree segmentation network is proposed by combining PointNet++ and convolutional neural network in an end-to-end manner. In the pre-segmentation stage, the local and global features of the input point cloud data are hierarchically extracted, and the latent feature matrix of the point cloud data is constructed; thus their similarity matrix and the confidence map can be created by two network branches respectively. Here, the similarity matrix measures their similarity between each pair of sampling points and determines the sampling points with high similarity to be the same instance thus forming a prediction group, whilst the confidence map reflects the degree of confidence of the prediction of each instance and filters the prediction group with low confidence to ensure its segmentation reliability and accuracy. In order to further improve the segmentation results, an adaptive K-nearest neighbor (A-KNN) propagation module for point cloud data is introduced in the fine segmentation stage to smooth the pre-segmentation results and also to reduce the misjudgment of the individual tree segmentation of sampling points. Experimental results demonstrate that our proposed method can effectively employ the spatial information and local features of point cloud data, and also greatly improve the accuracy and robustness of individual tree segmentation results owing to A-KNN label propagation, such as the average accuracy of individual tree segmentation on our labelled dataset is 96.33%, and its mIoU is 0.920 6.

     

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