Research map / 3D vision / Gaussian splatting
Horizon-GS: Unified 3D Gaussian Splatting for Large-Scale Aerial-to-Ground Scenes
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Horizon-GS unifies aerial and street view reconstruction with Gaussian splatting via a coarse-to-fine two-stage training, balanced camera sampling, and a new partly synthetic, partly real aerial-street dataset.
Problem
Unified reconstruction and rendering of large-scale scenes from both aerial and street views is hard because conflicting densification gradients and imbalanced camera coverage degrade single-model Gaussian splatting, and calibrated cross-view datasets are scarce.
Approach
A two-stage coarse-to-fine training: stage one builds coarse geometry from aerial views only, stage two freezes the MLPs and refines with street views using a new significance-based densification criterion, combined with a view-sampling ratio that balances aerial and street images and a view-dependent multi-level LOD scheme built on Scaffold-GS anchors.
Key results
- On the synthetic Block Small scene, Horizon-GS reaches 30.59 PSNR for aerial views versus 28.44 for Scaffold-GS and 25.44 for 3D-GS.
- On the large-scale Hillside Summer scene, Horizon-GS reaches 31.09 aerial PSNR versus 25.46 for Scaffold-GS* and 24.89 for Vast-GS.
- Horizon-GS achieves real-time rendering at 51.5 FPS on the Hillside Morning and Hillside Summer scenes, with about four hours of training per scene.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add balanced camera distribution (ablation) | Horizon-GS · Road aerial | PSNR: 22.49 -> 23.23 | Helped |
| Add balanced densification between training stages (ablation) | Horizon-GS · Road aerial | PSNR: 23.02 -> 23.23 | Helped |
| Add multi-resolution LOD (ablation) | Horizon-GS · Road aerial | PSNR: 23.05 -> 23.23 | Helped |
| Use the proposed second-stage densification policy instead of Scaffold-GS densification (ablation) | Horizon-GS · Road aerial | PSNR: 22.83 -> 23.23 | Helped |
| Train with Horizon-GS rather than UC-GS | UC-GS dataset · UC-GS held-out views | PSNR: 25.95 -> 25.35 | Hurt |
| Train with Horizon-GS rather than UC-GS | UC-GS dataset · UC-GS View(+1m) | PSNR: 23.52 -> 25.46 | Helped |
Surprising findings
- Joint training of aerial and street views underperforms separate training, with fewer final Gaussian primitives as more views are added.
- Hierarchical-3DGS remains competitive on street views in several scenes, attributed to its street-focused design.
Limitations
- Relies on dense multi-view input and depth supervision from pretrained monocular depth or rendering engines.
- Real-data quality is lower than synthetic due to pose estimation, sensor noise, and texture complexity.
- Assumes Manhattan world with z-axis perpendicular to ground.
Experimental setup
Datasets: MatrixCity UC-GS dataset Horizon-GS captured aerial-street dataset
Benchmarks: Block Small Block A Hillside Morning Hillside Summer UC-GS NYC and SF Real captured Road and Park scenes
Metrics: PSNR SSIM LPIPS FPS
Baselines: 3D-GS Scaffold-GS Hierarchical-3DGS 2D-GS UC-GS Vast-GS City-GS
Builds on: 3D Gaussian Splatting Scaffold-GS 2D Gaussian Splatting Octree-GS VastGaussian
Closest papers by meaning
- MS-GS: Multi-Appearance Sparse-View 3D Gaussian Splatting in the Wild (NeurIPS 2025 · similarity 0.91)
- Generative Sparse-View Gaussian Splatting (CVPR 2025 · similarity 0.90)
- EVolSplat: Efficient Volume-based Gaussian Splatting for Urban View Synthesis (CVPR 2025 · similarity 0.90)
- GS-IR: 3D Gaussian Splatting for Inverse Rendering (CVPR 2024 · similarity 0.90)
- SplatFormer: Point Transformer for Robust 3D Gaussian Splatting (ICLR 2025 · similarity 0.90)
- PUP 3D-GS: Principled Uncertainty Pruning for 3D Gaussian Splatting (CVPR 2025 · similarity 0.90)
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