Abstract
In recent years, the terrestrial laser scanning system (TLS) has become one of the most popular remote and nondestructive testing (NDT) methods for diagnostic measurements of buildings and structures as well as for the assessment of architectural heritage. Apart from 3D coordinates, the power of a laser beam backscattered from the scanned object can be captured by TLS. The radiometric information of the point cloud, called “intensity”, can provide information about changes in the physio–chemical properties of the scanned surface. This intensity can be effectively used to detect defects in the surfaces of walls, such as cracks and cavities, moisture, biodeterioration (mosses and lichens) or weathered parts of the wall. Manufacturers of TLS mainly use two different principles for distance measurement, time-of-flight (TOF) and phase-shift (PS). The power of energy in both types of rangefinders might be absorbed or reflected in a slightly different way and provide more or less detailed radiometric point cloud information. The main aim of this investigation is to compare TOF and PS scanners in the context of using TLS intensity data for the diagnostics of buildings and other structures. The potential of TLS intensity data for detecting defects in building walls has been tested on multiple samples by two TOF (Riegl VZ400i, Leica ScanStation C10) and two PS (Z + F 5016 IMAGER, Faro Focus3D) scanners.
Highlights
Structural safety, especially of old and historic buildings, is a very important issue in civil engineering
All point clouds from the two measurement campaigns were parsed from their own native formats to *.ptx files
The intensity of point clouds from different scanners was fit to the same scale from 0 to 1
Summary
Structural safety, especially of old and historic buildings, is a very important issue in civil engineering. The geometrical documentation and detection of the visible surface imperfections of buildings and other structures is a key element for their preservation. Application of well-known and very popular nondestructive testing (NDT) methods, such as rebound hammer test and ultrasonic pulse velocity test are impossible [1,2], because the methods require direct access to the tested element or structure. In this context, data acquisition without any physical contact of the research object is of special interest for measuring the technical condition of architectural structures. With speed and remote acquisition of data, the high accuracy mapping of real objects via a terrestrial laser scanner (TLS)
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