Automatic extraction of buildings from high-resolution remote sensing images becomes an important research. Since the convolutional neural network can perform pixel-level segmentation, this technology has been applied in this field. But the increase in resolution prone to blurry segmentation because the model needs more edge detail and multi-scale detail learning. To solve this problem, a method is proposed in this paper, which consists of three parts: (1) an improved model named Holistically-Nested Attention U-Net (HA U-Net) is designed, which integrates the attention mechanism and multi-scale nested modules to supervise prediction; (2) During model training, an improved weighted loss function is proposed to make the designed model more focused on learning boundary features; (3) watershed algorithm is exploited for image post-processing to optimize segmentation results. The designed HA U-Net performs well on WHU Building Dataset and Urban3d Challenge dataset, and achieves 9.31%, 2.17% better F1-score and 10.78%, 1.77% better IOU than the standard U-Net respectively. The experimental results indicate that the proposed method can well solve the building adhesion problem. The research can serve as updating geographic databases.INDEX TERMS Deep learning, building extraction, holistically-nested neural network, attention mechanism, weight mapping, watershed algorithm.
Deep convolutional neural network (CNN) has been increasingly applied in interpretation of remote sensing image such as automatically mapping land cover. Although the automatic CNN method achieves relatively high accuracy, there are still many misclassified areas. Considering that it is still far from practical application, this paper proposes a semi-automatic auxiliary scheme for land cover classification whose core idea is to use an interactive segmentation network. To infer the rough positions and categories of objects, a CNN is relied on to classify images in a patch-wise manner. Then an interactive segmentation method is proposed by accepting user-clicks on the inside and outside of object to guide the model for the segmentation task in the patches. This model also introduces different interactive modules to better integrate features of different scales. In addition, we create a large-scale sample library containing five common land cover categories which covers Jiangsu Province, China, and includes both aerial and satellite imagery. On our sample, we gave a thorough evaluation of most recent deep learning-based methods. The experimental results shown by our interactive segmentation also far outperform the recent semantic segmentation method, which provides a reference for semi-automatic land cover mapping.INDEX TERMS deep learning; CNN; sample; interactive segmentation.
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