Classification With an Edge: Improving Semantic Image Segmentation with Boundary Detection
This work addresses a specific issue in remote sensing by improving boundary clarity in semantic segmentation, though it is incremental as it builds on existing architectures like Segnet and FCN.
The paper tackles the problem of blurry object boundaries in semantic segmentation by integrating semantically informed edge detection into deep convolutional neural networks, achieving over 90% overall accuracy on the ISPRS Vaihingen benchmark.
We present an end-to-end trainable deep convolutional neural network (DCNN) for semantic segmentation with built-in awareness of semantically meaningful boundaries. Semantic segmentation is a fundamental remote sensing task, and most state-of-the-art methods rely on DCNNs as their workhorse. A major reason for their success is that deep networks learn to accumulate contextual information over very large windows (receptive fields). However, this success comes at a cost, since the associated loss of effecive spatial resolution washes out high-frequency details and leads to blurry object boundaries. Here, we propose to counter this effect by combining semantic segmentation with semantically informed edge detection, thus making class-boundaries explicit in the model, First, we construct a comparatively simple, memory-efficient model by adding boundary detection to the Segnet encoder-decoder architecture. Second, we also include boundary detection in FCN-type models and set up a high-end classifier ensemble. We show that boundary detection significantly improves semantic segmentation with CNNs. Our high-end ensemble achieves > 90% overall accuracy on the ISPRS Vaihingen benchmark.