FLASH3R: On-Board Incremental Dense 3D Aerial Reconstruction with Progressive Geometry Guided Visual Geometry Grounded Transformer

Background and Motivation

UAV photogrammetry is increasingly used for time-sensitive field tasks such as emergency response, disaster inspection, and infrastructure monitoring. In these scenarios, the basic requirement is not only to acquire 2D orthophotos, but to generate real-time, geo-referenced 3D information that can support deformation analysis, volume estimation, and rapid decision-making.

Conventional on-board pipelines are often limited to digital orthophoto maps (DOM), while full sparse-to-dense reconstruction remains computationally expensive for edge UAV platforms. Flash3R targets this gap by combining incremental SfM with feed-forward visual geometry inference, enabling dense 3D reconstruction directly on the UAV without depending on cloud computation.

• Sparse-Dense Dual-Branch Parallel Reconstruction
• Image-Level and Point-Level Dense-to-Sparse Alignment
• Edge Device Deployment Validation

Pipeline

Flash3R processes successive UAV image batches through three compact stages:

• Sparse Pipeline: geo-referenced SfM scaffold
• Dense Pipeline: transformer-based dense geometry inference
• Two-Level Alignment: image-level pose refinement and point-level MLS correction