Abstract
Terrestrial Laser Scanning (TLS) is a well-established technique for remote acquisition of geometrical data of a tested object. For the past two decades it has been commonly used in geodesy, surveying and related areas for acquiring data about spacing of civil engineering structures and buildings. An average TLS apparatus, apart from 3D coordinates registers radiometric information of laser beam reflectance. This radiometric information of the laser beam reflectance is usually called intensity and has no meaning for solely geometric measurements. Nevertheless, the value of intensity depends mainly on physicochemical properties of scanned material such as roughness, colour and saturation. Keeping these facts in mind, authors suggest using changes in value of intensity to locate various imperfections on a brick wall. So far, authors have conducted a thorough and successful research programme dedicated to detection of saturation and saturation movement in brick walls. Based on this experience a new research programme was conducted focused on various aspects of detection of brick wall defects. The main aim of the paper is to present the possibility of using the intensity value in for the diagnostics of the technical condition of a brick walls. Advantages and limitations of harnessing TLS for detection of surface defects of brick walls are presented and discussed in the paper.
Highlights
In order to evaluate the building or structure safety, the Terrestrial Laser Scanning diagnostic measurement is one of the most important and modern methods
The main aim of the paper is to present the possibility of using the intensity value in for the diagnostics of the technical condition of a brick walls
In the diagnostic tests of buildings conducted with Terrestrial Laser Scanning (TLS), the value of intensity is increasingly used as a key measurement result
Summary
In order to evaluate the building or structure safety, the Terrestrial Laser Scanning diagnostic measurement is one of the most important and modern methods. The power of backscattered light from the scanned objects mainly depends on the transmitted signal power, the system transmission factor ( Sys), the atmospheric transmission factor ( Atm), the distance (R), the incident angle effect ( ) and the reflectance of a material (ρ). The parameters PT and Sys can be considered constant They depend on the a scanner technical specifications e.g.: type and power of a rangefinder (phase-shift based or timeof-flight technology), wavelength of a laser, aperture diameter of TLS, sensitivity of a detector etc. In the case of disturbance of the homogeneous surface of buildings or structures, which are caused by cavities and cracks, the power of the laser beam reflectance should be significantly changed due to the changes in roughness and colour of the surface. Cavities, cracks and moisture of a building wall can be detected by an appropriate interpretation of the intensity value
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