What is Ground Sample Distance (GSD)

The integration of close-range photogrammetry and terrestrial laser scanner enables reality-based modeling procedures that can help BIM modeling for existing buildings. The restitution of virtual models from high-resolution surveys is a complex process that requires much expertise. It incorporates concepts of resolution, accuracy, and precision in the acquisition phase; filtering, registration, and decimation for point cloud elaboration; and meshing, texturing, simplification, segmentation, and feature extraction in the final modeling stage. The previous steps are the same whether the ultimate goal is a classic 2D representation or a 3D one. For BIM modeling, the job becomes challenging because the necessary simplification of the model cannot be automatized and apparently collides with the high resolution and fidelity of original surveyed data. This chapter presents the process of surveying and 3D modeling of the Ghesc village, following the whole path from data acquisition to BIM modeling, discussing strengths and weakness, issues, and recent solutions for restoration interventions.