LangLoc: Language-Driven Localization via Formatted Spatial Description Generation

Existing localization methods commonly employ vision to perceive scene and achieve localization in GNSS-denied areas, yet they often struggle in environments with complex lighting conditions, dynamic objects or privacy-preserving areas. Humans possess the ability to describe various scenes using natural language, effectively inferring their location by leveraging the rich semantic information in these descriptions. Harnessing language presents a potential solution for robust localization. Thus, this study introduces a new task, Language-driven Localization, and proposes a novel localization framework, LangLoc, which determines the user's position and orientation through textual descriptions. Given the diversity of natural language descriptions, we first design a Spatial Description Generator (SDG), foundational to LangLoc, which extracts and combines the position and attribute information of objects within a scene to generate uniformly formatted textual descriptions. SDG eliminates the ambiguity of language, detailing the spatial layout and object relations of the scene, providing a reliable basis for localization. With generated descriptions, LangLoc effortlessly achieves language-only localization using text encoder and pose regressor. Furthermore, LangLoc can add one image to text input, achieving mutual optimization and feature adaptive fusion across modalities through two modality-specific encoders, cross-modal fusion, and multimodal joint learning strategies. This enhances the framework's capability to handle complex scenes, achieving more accurate localization. Extensive experiments on the Oxford RobotCar, 4-Seasons, and Virtual Gallery datasets demonstrate LangLoc's effectiveness in both language-only and visual-language localization across various outdoor and indoor scenarios. Notably, LangLoc achieves noticeable performance gains when using both text and image inputs in challenging conditions such as overexposure, low lighting, and occlusions, showcasing its superior robustness.