  In this paper, we introduce the task of visual grounding for remote sensing
data (RSVG). RSVG aims to localize the referred objects in remote sensing (RS)
images with the guidance of natural language. To retrieve rich information from
RS imagery using natural language, many research tasks, like RS image visual
question answering, RS image captioning, and RS image-text retrieval have been
investigated a lot. However, the object-level visual grounding on RS images is
still under-explored. Thus, in this work, we propose to construct the dataset
and explore deep learning models for the RSVG task. Specifically, our
contributions can be summarized as follows. 1) We build the new large-scale
benchmark dataset of RSVG, termed RSVGD, to fully advance the research of RSVG.
This new dataset includes image/expression/box triplets for training and
evaluating visual grounding models. 2) We benchmark extensive state-of-the-art
(SOTA) natural image visual grounding methods on the constructed RSVGD dataset,
and some insightful analyses are provided based on the results. 3) A novel
transformer-based Multi-Level Cross-Modal feature learning (MLCM) module is
proposed. Remotely-sensed images are usually with large scale variations and
cluttered backgrounds. To deal with the scale-variation problem, the MLCM
module takes advantage of multi-scale visual features and multi-granularity
textual embeddings to learn more discriminative representations. To cope with
the cluttered background problem, MLCM adaptively filters irrelevant noise and
enhances salient features. In this way, our proposed model can incorporate more
effective multi-level and multi-modal features to boost performance.
Furthermore, this work also provides useful insights for developing better RSVG
models. The dataset and code will be publicly available at
https://github.com/ZhanYang-nwpu/RSVG-pytorch.
