Using the scanners and drone for comparison of point cloud accuracy at traffic accident analysis.

The purpose of the paper is to describe, compare and analyse the instruments used, time needed and accuracy of gathered data, sketches, 3D models and to enhance the extracted information about the accident. Simple sketches and tape measurements were performed. Also complex 3D measurements and 3D modelling of the scene with Terrestrial Laser Scanners (TLS) and Unmanned Aerial Vehicle (UAV) technology were used. A classical police work dealing with a simulated traffic accident was compared to sketches obtained from 3D models from Riegl VZ-400i 3D, Faro Focus S70, Geoslam ZebRevo 3D TLS and Topcon Falcon 8 drone. For 3D modelling an orthophoto from drone photos and point clouds were obtained. 3D models were graphically compared in CloudCompare software. Sketches were made for each measuring method and their accuracies were also compared one to each other. The graphical distance accuracy in scene measurements ranged up to 17 cm in comparison to police measurement but in the most course point cloud. Average absolute difference in compared distances amounts up to 6 cm. As expected, more points in the cloud means better 3D model and easier analysis. There is considerable reduction of time needed for collecting the accident scene data. The obtained 3D model is a permanent archive of the scene of a traffic accident. From the cadre, both visual and dimensional information subsequently can be obtained.