A Semi-Automatic Roof Type-Driven Workflow for LoD2 Building Reconstruction from Orthophotos and Photogrammetric Point Clouds

This paper presents a semi-automatic workflow for building LoD2 3D city models, in which users digitize roof outlines from orthophotos and label roof types (flat, gable, hip, shed, pyramid), and rule-based code then reconstructs roof geometry using height and orientation derived from point cloud elevation layers. Applied to 371 buildings, the method outputs CityJSON models convertible to CityGML. On 30 buildings, roof-plane completeness averaged 100% and correctness and quality averaged 98.33%, with a geometric RMSE of 0.90 m.