The gantry crane, for its part, travels on a track made of rails laid directly on the ground. The two beams forming its width are joined together. At the top of the assembly, running lengthwise, are two longitudinal beams, also joined together, on which rests a track made of rails. A trolley travels on these rails, supporting the lifting equipment itself, which consists of one or two winches around which the lifting cables are wound, as well as the gripping device, which can be a hoist, a hydraulic clamp, a grapple, or an electromagnet. These gantries generate significant work for surveying technicians: - Geometric signatures (recording of the wireframe and monitoring of deformations) using retroreflective targets installed at strategic joints - Expert assessments following damage - Monitoring of boom closure trajectories - Layout and monitoring of translation rails on the ground and in the boom - 3D laser scanning (simulation of clearance and unloading phases)