3D digitization of ancient city walls based on structured light scanning

To support the management and conservation of ancient city walls, high-quality 3D digital documentation should be systematically integrated into heritage documentation and monitoring processes. This paper presents a high-definition, large-scale 3D digitization method for ancient city walls. Structured Light Scanning (SLS) is introduced for the first time as a flexible approach to acquire high-resolution masonry surface data. A tailored brick-outline registration (BOR) algorithm is proposed by exploiting the regular brick geometry, which incorporates SLS phase information for robust feature extraction and multi-modal data collaboration. The proposed method is validated on the Nanjing City Wall, achieving high-quality 3D digitization over tens of square meters while preserving fine inscriptions and structural details. This work provides an effective solution for the digital archiving of large-scale heritage masonry structures.