Accuracy investigation of point clouds with Faro Focus 3d S120 terrestrial laser scanner

Lviv Polytechnic National University
Lviv Polytechnic National University

Aim. Terrestrial laser scanning is a powerful method for collecting spatial data. This method of remote sensing allows fast, non-contact and precise measurement of objects. Terrestrial laser scanning systems deliver 3D coordinates and the power of the backscattered laser scan signal of each point which registered it as an intensity value. Intensity values are affected by the characteristic of the measured object and the parameters of the environment. The backscattered electromagnetic signal is influenced in its strength by the reflectivity of the scanned object surface, the incidence angle, the distance between laser scanner and object and the atmospheric respectively system specific setting of the TLS-measurement. Since details about system internal alteration of the signal are often unknown to the user, model driven approaches are impractical. On the other hand, existing data driven calibration procedures require laborious acquisition of separate reference datasets or areas of homogenous reflection characteristics from the field data. Therefore, the impact of qualitative and quantitative characteristics of the scanning object for accuracy investigation of point clouds with the Faro Focus 3D S120 terrestrial laser scanner is the aim of work. Methods. According to the tasks, an experiment was performed, which was to investigation the point clouds: density, interval between points, and intensity changes with distance and color of the scanning object. Faro Focus 3D S120 terrestrial laser scanner was used for the research. As a special test target was chosen a polished glass plate with size 30 cm × 30 cm, which was twice covered with an aerosol with white matte paint with a reflectivity of about 80% on one side of the target and black matte paint with a reflectivity of about 20% on the other side of the target. To perform the experimental work, the test target was mounted on a tripod using a sleeve that attaches to the target. The target was placed on the white side at a distance of 0.6 m from the terrestrial laser scanner and was scanned. Then the target was turned to the black side and the scanning was repeated. The measurements were repeated at distances of 1.5 m, 3 m, 5 m and 10m. Our test data covers 10 terrestrial scans. The intensity values were exported from the point clouds using Faro SCENE software. Results. The results of the experimental work were considered for the fragments of point clouds of black and white sides of the test target (the size of the fragment is 15x15 points). The distribution of point clouds in the YX and YZ planes of the upper left and center fragments of the white and black sides of the targets, the intensity of the reflected signal and the standard deviation of the intensity values were analyzed. Scientific novelty. The influence of the qualitative and quantitative characteristics of the scanning object on the accuracy of point clouds construction with the Faro Focus 3D S120 laser scanner is presented and analyzed. Practical significance. The study will optimize the choice of terrestrial laser scanning settings based on the properties of the object and the scanning distance.

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