What is the Laser Scanner
In the process of innovation that La SIA has been undertaking for the past few years by embracing the BIM methodology throughout the architecture sector, it could not miss updating the techniques of building surveying. The company has equipped itself with a state-of-the-art 3D Laser Scanner station for digital surveying using non-invasive techniques of civil and industrial works.
What is the Laser Scanner
The Laser Scanner is a very high-precision direct measurement tool for three-dimensional object detection. The instrument can measure hundreds of thousands of points with a very high speed to define the surface of the detected object. The result obtained is a very dense set of spatial coordinates that form the so-called “point cloud.”
The principle behind the “measurement” of each individual point is the difference between the light signal (laser) emitted and the signal received by the machine. Almost all modern laser scanners can be divided into two macro-categories depending on the technique used: phase shift based and time-of-flight based (TFT). The former use the phase difference between the two signals to find the distance to the point while the latter category uses the time difference between sending and receiving the laser signal.
From the “cloud” to the 3D model
Each time a laser scan (station) is performed, the instrument generates a “point cloud.” At the end of the survey, all the clouds generated using special software should be merged. Depending on the complexity of the survey and the degree of detail desired, the number of stations to be performed increases; ranging from 4 or 5 to survey an apartment to over 100 for the exterior survey of an Outlet as depicted below.
Modern laser scanners also mount an HDR digital camera to capture images of the previously detected space. This allows each detected point to be “colored,” resulting in a kind of 360-degree panoramic photo from the scanning point.
The potential of these surveys lies in the fact that each point, being embedded in a precise geometric space characterized by x,y,z Cartesian coordinates, is measurable, and with the addition of a georeferenced point the whole model takes on a precise location in real physical space.
There are many software programs that can work directly on point clouds to create surfaces, solids, planes, make comparisons between different clouds or with other solid objects (interferences), and create navigable models. Therefore, the point cloud lends itself as an excellent starting point for the realization of the three-dimensional model. In modern projects of restoration or extension of buildings, especially historic ones, the acquisition of the existing by point cloud cannot be disregarded not so much for the speed of the survey execution but, above all, for the accuracy of the obtained model.
Thus, moving from the point cloud to a 3-D model is a straightforward step that LaSIA has decided to adopt in all projects that involve surveying the existing. Within the company, the combination of “point cloud” and BIM has become a “must.” As part of research and development, experiments are also being conducted for the survey and BIM restitution of unconventional “objects” in collaboration with the University of Cagliari.
In addition to surveying in architecture, the laser scanner is also very effective in piping, whether in small thermal power plants or large petrochemical plants; in some cases it is the only tool that can identify changes and modifications undergone by the plant.
Conclusions
In this area, too, the company’s desire for continuous evolution in working methodologies as well as in instrumentation (hardware and software) has entailed considerable investment both in economic terms and, above all, in terms of human resources. The company has acquired and trained staff by specializing them to use and take full advantage of these technologies.
