Correction of Intensity Incidence Angle Effect in Terrestrial Laser Scanning

Abstract

KEY WORDS:Terrestrial laser scanning, Laser scanning intensity, incidence angle effect, ABSTRACT:In this article, we have studied the incidence angle effect on Terrestrial Laser Scanning (TLS) intensity. In previous tests, it has been found that the backscattered intensity of an object affects the incidence angle effect. We made additional experiments to investigate the potential mixing of distance and incidence angle effects and the role of surface parameters such as object grain size and scanning wavelength. The results indicate that distance and incidence angle effects do not mix and laboratory measured correction values can be used to correct intensity data from field-scanned point clouds. We also compared the laboratory measurements to real world surfaces to validate the correction procedures in practical TLS applications. The idea is also to make practical recommendations for TLS intensity correction in most common TLS applications.* Corresponding author. This is useful to know for communication with the appropriate person in cases with more than one author.

A non-destructive technique for health assessment of fire-damaged concrete elements using terrestrial laser scanning

“…As the scanning distance increased, the incidence angle decreased and both scanners used showed the same trend as shown in Fig. 7 and 8 below: In line with the above findings, Krooks et al [26] also investigated the relation between incidence angle and distance (range) and it has been reported that in several fieldwork applications of static TLS where a survey is conducted with the scanner mounted on the tripod, changes in the angle of incidence occur as the measurement range increases. …”

“…In a similar vein, Krooks et al [26] also reported that distance and incidence angle effects on the intensity do not mix, implying that a correction of both effects is possible by using different models that are independent of the measurement.…”

“…It has been reported that higher incidence angles of for instance 20° and more lead to diminished returned intensity [26]. The results presented below are for blocks that were scanned at incidence angles less than 12° and with the scanning distance held fixed.…”

“…(5) is a suitable physical based model under the assumptions mentioned above. However, in reality different relations have been observed between intensity and range for TLS than described by the physical model at near distances due to factors such as instrumental effects [27,33,26,31] causing the physical model to be inapplicable at all scanning distances. Theoretically, the effects of the range and the angle of incidence on the intensity have been found to be independent, implying that it is possible to solve each one of them separately.…”

“…The addition of intensity data to the geometric data has proved useful in several applications [19,26,27] and a study by Teza et al [20] showed a successful method based on curvature analysis of TLS geometric data and aimed at recognizing surface defects of a concrete bridge due to mass loss. However, laser scanner intensity data is not often utilised, because it is affected by several factors such as scanning distance and incidence angle, water content, ambient light, humidity, type of laser and object surface properties [21,22].…”