Multitarget Domain Adaptation Building Instance Extraction of Remote Sensing Imagery With Domain-Common Approximation Learning

Deep learning-based building instance extraction on remote sensing imagery (RSI) has achieved tremendous success under the large-scale labeled training data. However, multi-target domain adaptation building instance extraction (MD-BIE) is still a challenge task that involves transferring knowledge from a source domain to multiple unlabeled target domains, which poses various semantic gaps between and within multiple domains, e.g ., style, illumination, resolution, density, scale, etc. Most current methods for single-target domain adaptation are not applicable to the more realistic MD-BIE task. To this end, we propose a novel Domain-common Approximation Learning (DAL) for both modelling intra-domain and inter-domain adaptation, thus obtaining robust MD-BIE. DAL contains three main modules: multi-domain style transfer (MST), multi-domain feature approximation (MFA), and multi-domain cascaded instance extraction (MCIE). To alleviate the semantic gaps between multiple domains for inter-domain adaptation, we first employ the MST to learn multiple target-domain-like features that preserve both the styles of target domains and the content of the source domain, and then use the MFA to approximate these features towards a central domain-common space, thus producing domain-common semantic representations. Moreover, we develop the MCIE with hierarchical extraction losses for intra-domain adaptation to extract precise building instance contours from the domain-common semantic representations, further eliminating the potential gaps within multiple domains. By co-learning these three modules in an end-to-end manner, the DAL bridges the semantic gaps between and within multiple domains. Extensive experiments on different popular MD-BIS tasks (SAB → Crowd & WHU, Crowd → SAB & WHU, SAB → Crowd & SAB & WHU and SAB → WHU) show that our DAL outperforms the current methods by a significant margin.