Efficient Reverse Engineering of Ship Hulls through Photogrammetry and NURBS

We present an efficient workflow to update existing ship documentation with as-measured ship geometry, accounting for modifications and age-related deformations. The goal is to provide geometric data in a 2D lines plan that can instantly update a compatible 3D digital model. This method is demonstrated through a case study involving a vessel requiring a replacement of its aft section. We used a low-cost photogrammetry procedure to capture the full-field geometry of the new section and integrate it with existing documentation. Agisoft Metashape software and consumer-grade equipment facilitated the photogrammetry, while Rhinoceros software helped capture a polyline-based 2D lines plan from the polygon mesh model. The polylines were then processed into splines to create a NURBS-based 3D model of the measured hull. By ensuring continuity and smoothness, we successfully integrated the newly measured stern shape into the existing 2D and 3D documentation. This method is cost-effective, reproducible, accurate, and time-efficient, offering a viable alternative to more expensive Terrestrial Laser Scanning methods. A skilled individual can complete the measurements and processing in two days. Our adaptable workflow supports the repair, modification, and retrofitting of ships, regardless of the specific software or hardware used.