  Road extraction in remote sensing images is of great importance for a wide
range of applications. Because of the complex background, and high density,
most of the existing methods fail to accurately extract a road network that
appears correct and complete. Moreover, they suffer from either insufficient
training data or high costs of manual annotation. To address these problems, we
introduce a new model to apply structured domain adaption for synthetic image
generation and road segmentation. We incorporate a feature pyramid network into
generative adversarial networks to minimize the difference between the source
and target domains. A generator is learned to produce quality synthetic images,
and the discriminator attempts to distinguish them. We also propose a feature
pyramid network that improves the performance of the proposed model by
extracting effective features from all the layers of the network for describing
different scales objects. Indeed, a novel scale-wise architecture is introduced
to learn from the multi-level feature maps and improve the semantics of the
features. For optimization, the model is trained by a joint reconstruction loss
function, which minimizes the difference between the fake images and the real
ones. A wide range of experiments on three datasets prove the superior
performance of the proposed approach in terms of accuracy and efficiency. In
particular, our model achieves state-of-the-art 78.86 IOU on the Massachusetts
dataset with 14.89M parameters and 86.78B FLOPs, with 4x fewer FLOPs but higher
accuracy (+3.47% IOU) than the top performer among state-of-the-art approaches
used in the evaluation.
