Scale-Aware UAV-to-Satellite Cross-View Geo-Localization: A Semantic Geometric Approach

TL;DR

This paper introduces a semantic geometric framework that estimates absolute scale from UAV images using vehicles as references, enhancing cross-view geo-localization robustness under scale ambiguity.

Contribution

It proposes a novel decoupled stereoscopic projection model and a dual-dimension fusion strategy to accurately recover scale from monocular UAV images for improved geo-localization.

Findings

Significantly improves CVGL robustness under unknown scales.

Enhances UAV altitude estimation accuracy.

Facilitates 3D model scale recovery.

Abstract

Cross-View Geo-Localization (CVGL) between UAV imagery and satellite images plays a crucial role in target localization and UAV self-positioning. However, most existing methods rely on the idealized assumption of scale consistency between UAV queries and satellite galleries, overlooking the severe scale ambiguity commonly encountered in real-world scenarios. This discrepancy leads to field-of-view misalignment and feature mismatch, significantly degrading CVGL robustness. To address this issue, we propose a geometric framework that recovers the absolute metric scale from monocular UAV images using semantic anchors. Specifically, small vehicles (SVs), characterized by relatively stable prior size distributions and high detectability, are exploited as metric references. A Decoupled Stereoscopic Projection Model is introduced to estimate the absolute image scale from these semantic targets. By decomposing vehicle dimensions into radial and tangential components, the model compensates for perspective distortions in 2D detections of 3D vehicles, enabling more accurate scale estimation. To further reduce intra-class size variation and detection noise, a dual-dimension fusion strategy with Interquartile Range (IQR)-based robust aggregation is employed. The estimated global scale is then used as a physical constraint for scale-adaptive satellite image cropping, improving UAV-to-satellite feature alignment. Experiments on augmented DenseUAV and UAV-VisLoc datasets demonstrate that the proposed method significantly improves CVGL robustness under unknown UAV image scales. Additionally, the framework shows strong potential for downstream applications such as passive UAV altitude estimation and 3D model scale recovery.