Asymmetric Cascade Fusion Network for Building Extraction

The U-Net-like model has been widely studied in the field of building extraction. However, most of these models are based on locally sensed convolutional neural networks (CNNs) designed with symmetric structure and single feature processing, which cannot accurately identify buildings with different sizes, shapes, and colors in remote sensing images. To overcome these problems, we propose the asymmetric cascade fusion network (ACFN), based on the vision transformer (ViT), to design a novel asymmetric architecture to recognize buildings of different sizes and shapes by processing multigranularity features by different means. First, the asymmetric architecture obtains multigranularity features with global contextual information by embedding different types of attention in encoder-decoders of different sizes. This architecture can identify densely distributed and occluded buildings by semantic reasoning in remote sensing images with complex information. Second, we design a multibranch weighted pyramid pooling module (MWPPM), which sets different branch weights to offset the background noise introduced in introducing global contextual information. Our ACFN significantly improves the Beijing buildings, ISPRS-Vaihingen, and LoveDA datasets.