Language Query-Based Transformer With Multiscale Cross-Modal Alignment for Visual Grounding on Remote Sensing Images

Visual grounding for remote sensing images (RSVG) aims to localize the referred objects in the remote sensing (RS) images according to a language expression. Existing methods tend to align visual and text features followed by concatenation and then employ a fusion Transformer to learn a token representation for final target localization. However, simple fusion Transformer structure fails to sufficiently learn the location representation of referred object from the multimodal features. Inspired by the detection transformer (DETR), in this article, we propose a novel language query-based Transformer framework for RSVG termed LQVG. Specifically, we adopt the extracted sentence-level text features as the queries, called language queries, to retrieve and aggregate representation information of the referred object from the multiscale visual features in the Transformer decoder. The language queries are then converted into object embeddings for final coordinate prediction of referred object. Besides, a multiscale cross-modal alignment (MSCMA) module is devised before the multimodal Transformer to enhance the semantic correlation between the visual and text features, thus facilitating the cross-modal decoding process to generate more precise object representation. Moreover, a new RSVG dataset named RSVG-HR is built to evaluate the performance of the RSVG approaches on very high-resolution RS images with inconspicuous objects. Experimental results on two benchmark datasets demonstrate that our proposed method significantly surpasses the comparison methods and achieves state-of-the-art performance. The dataset and code are available at
https://github.com/LANMNG/LQVG
.