Harnessing Terrestrial Laser Scanning for Monitoring of Saturation of Buildings

Abstract

A type of scanned surface (its physico-chemical properties) significantly influences the power of the returning laser signal in terrestrial laser scanner technique. The influence of different colour and rough-ness of a scanned surface on absorption and scattering was proven by multiple researchers. Water is characterized by high absorption coefficient of a laser signal. Keeping this fact in mind authors prepared a research programme focused on the influence of moisture movement in building wall on the value of the intensity in TLS. An impulse TLS scanner ScanStation C10 produced by Leica was used during the research programme in an indoor environment. The measurements were conducted targeting specially formed walls made of cellular concrete and ceramic hollow blocks. Test objects were placed in a special plastic container with water. The level of the water in the container was kept constant using an autonomous hydraulic pressure system. The porous dry wall was sucking water and the level of saturation was rising. The differences in values of intensity point cloud from scan were of special interest. In addition, tests have been carried out to the building object in an outdoors environment. Achieved results have shown that the intensity of the reflected laser beam from the wet building materials is much lower than that of dry materials. This dependency can be used for the measurement of TLS in the geodetic monitoring. Apart from determining the geometry of a building wall, it is possible to determine changes its humidity. Keywords: terrestrial laser scanner, intensity, humidity, geodetic monitoring