Analysis of geometric and radiometric factors affecting measurement results of civil engineering structures with different scanning drone types

• Test fields were proposed to evaluate the measurement accuracy of scanning drones. • Geometric and radiometric factors affecting the accuracy results were analyzed. • The main comparison tool was surface deviation charts, which show objects integrity. • The main factors affecting the accuracy of UAV scanning were identified. Laser scanning using unmanned aerial vehicles (UAVs) offers new possibilities for accessing building structures, which can be useful for inventory, modeling, and safety assessment tasks. This measurement method still requires accuracy studies for detailed and precise shape determination of different infrastructures. This article presents the results of accuracy analyses for four scanning systems representing different levels of technological advancement in their component subsystems. Measurements were carried out in a test field containing various building and infrastructure objects. The study involved analyses related to geometric and radiometric factors affecting measurement results for different types of objects. Geometric factors included both the geometry of the laser spot and the geometry of characteristic elements of the scanned object. Tests were conducted on flat, truss, surface-oriented, curved, and slit objects. Radiometric factors were related to the response of the emitted laser beam after reflection from surfaces with different properties (material, color, structure). The main comparison tool was surface deviation charts, which show their value, location and scattering. Among the tested units, only one scanner, the AlphaAir 10, provided results that allowed for potential shape analysis of building objects. The next scanner, the Zenmuse L2, provided similar results, but only at low flight heights. The remaining scanners delivered results with high measurement noise, causing deterioration in detail recognition. The study illustrates a methodology for testing UAV scanners, involving the diverse scenarios, enables the identification of limitations of UAV systems and the determination of key parameters, that affect the reliability of data for engineering applications.