In this paper, we propose a Height-Aware Graph Convolution Network (HA-GCN) to solve the challenging problem of Airborne laser scanning (ALS) point cloud classification. For samples with uneven distribution and large differences in scale, classification using local features is unstable and easily affected by noise. Therefore, we use a multi-layer stacked Edge Convolution (EdgeConv) operators to extract local and global information at the same time. In addition, in view of the characteristics of the height distribution of airborne LiDAR point cloud, we introduce height attention weights as a supplement to feature extraction. First, the original point cloud is divided into sub-blocks and sampled to a fixed number of points. Then, the EdgeConv operator is used to extract local-global features. At the same time, the Height-Aware (HA) module is used to generate attention weights. Finally, the height attention weights are applied to the feature extraction network and the classification is completed after post-processing. The experimental results on the Vaihingen dataset show that the proposed method achieves the effect of the state-of-the-art methods in overall accuracy, as well as impressive results in single-category classification accuracy.
Recently, a complex-valued convolutional neural network (CV-CNN) has been used for the classification of polarimetric synthetic aperture radar (PolSAR) images, and has shown superior performance to most traditional algorithms. However, it usually yields unreliable results for the pixels distributing within heterogeneous regions or the edge areas. To solve this problem, in this paper, an edge reassigning scheme based on Markov random field (MRF) is considered to combine with the CV-CNN. In this scheme,both the polarimetric statistical property and label context information are employed. The experiments performed on a benchmark PolSAR image of Flevoland has demonstrated the superior performance of the proposed algorithm.
Most of the visual tracking algorithms are very sensitive to the initialized bounding-box of the tracking object, while, how to obtain a precise bounding-box in the first frame needs further research. In this paper, we propose an automatic algorithm to refine the references of the tracking object after a roughly selected bounding-box in the first frame. Based on the input rough location and scale information, the proposed algorithm exploits the region merger algorithm based on maximal similarity to segment the superpixel regions into foreground or background. In order to improve the segmentation effect, a feature clustering strategy is exploited to obtain reliable foreground label and background label and color histogram in HSI space is exploited to describe the superpixel feature. The final refinement bounding-box is the minimal enclosing rectangle of the foreground region. Extensive experiments are performed and the results indicate that the proposed algorithm can reliably refine the initial bounding-box relying only on the first frame information and improve the robustness of the tracking algorithms distinctively.