A survey by lasergrammetry will incorporate three key stages.
Firstly, the marking-out of the entire structure to be scanned will allow the identification of the number of stations to be used, the potential positions of the 3D scanner, and the type and number of markers (flat targets or spheres) to be installed; the selection of hardware and the number of devices will be defined beforehand in conjunction with the technical proposal.
Scanning proper, or “3D laser scanning”, will then account for 80% of the project time on site. The objective is to obtain measurements or “points” over the entire surface of installations which are visible and accessible by laser. To this end, the operator will record multiple viewpoints with the device, just as a photographer would do for the documentation of an entire site.
Back at Urbica, operators will then integrate all the stations (assembly) in one and the same point cloud. In order to allow data processing tools to read these files with no loss of speed, the filtering of superfluous points (segmentation) or points which are very close together (sampling) is recommended.