Abstract. Urban digital twins increasingly require pedestrian-scale three-dimensional (3D) representations to support accessibility and inclusiveness assessment. However, existing approaches typically emphasize either geometric accuracy or visual realism, while lacking an integrated framework for analysing pedestrian-level conditions. This study proposes a hybrid workflow integrating handheld LiDAR and 3D Gaussian Splatting (3DGS) within a CityGML-based semantic framework for accessibility assessment. Handheld LiDAR provides centimetre-level geometric measurements, enabling the extraction of key indicators such as slope, surface roughness, and obstacle presence. In parallel, 3DGS reconstruction from 360° video imagery enhances visual realism and perceptual understanding. Both datasets are co-registered and structured within the CityGML 3.0 Transportation model to represent pedestrian environments in a unified spatial and semantic framework. Accessibility assessment was conducted using three approaches: LiDAR-based analysis, field survey observations, and immersive evaluation in a Virtual Reality (VR) environment. The LiDAR-based results were used as reference. Comparative analysis shows that field survey assessment achieves an agreement of approximately 85.7%, while VR-based assessment reaches approximately 75.4%. The results indicate that while VR does not replace metric-based analysis, it enables perception-driven and participatory evaluation. In particular, VR-based assessment shows potential to involve users, including people with disabilities, in accessibility evaluation through immersive and remote interaction. The proposed approach contributes to the development of human-scale urban digital twins by integrating metric accuracy, semantic structure, and participatory evaluation for more inclusive accessibility analysis.
D. Suwardhi, Wahyunan Andika, R. Widyastuti et al.· The International Archives o...· 0 citations
Abstract. Urban digital twin systems require 3D city representations that reconcile semantic structure, geometric reliability, simulation capability, and photorealistic real-time rendering. Existing approaches usually prioritize a single modelling paradigm, limiting their ability to support both analytical and visualization needs. CityGML provides standardized semantics and topology but often lacks surface realism. Semantic mesh models preserve geometric detail suitable for environmental simulations but provide limited hierarchical semantics. In contrast, neural radiance-field approaches such as 3D Gaussian Splatting (3DGS) enable photorealistic rendering at interactive frame rates but do not explicitly encode topology or structured semantics. This study establishes a comparative framework linking LiDAR-derived CityGML, semantic mesh, 3D Gaussian Splatting, and Triangle Splatting within a unified urban modelling workflow. UAV data acquired using a DJI ZENMUSE L2 sensor serve as the geometric backbone for reconstructing CityGML LoD1–LoD2 models. The semantic model is transformed into a textured triangular mesh, while radiance-based models are generated from the same imagery using multiple 3DGS implementations and a triangle splatting framework. Comparative evaluation investigates geometric coherence, semantic preservation, and radiance consistency to identify structural correspondences across the representations. The results reveal complementary modelling layers that can be systematically mapped rather than treated as competing alternatives. Based on these findings, the paper proposes a conceptual foundation for a unified 3D urban model capable of transforming consistently into semantic, surface-based, and radiance-based representations for adaptive urban digital twin systems. Data are freely accessible for research purposes at https://github.com/3DOM-FBK/urban-representation-fusion/.
D. Suwardhi, Muhammad Arif Sudibyo, Agus Ambarwari et al.· The International Archives o...· 0 citations
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