Accuracy Assessment of Map Coordinates from Unmanned Aerial Vehicle

Abstract

Unmanned aerial vehicle (UAV) surveying and mapping data have not yet been clearly defined as a positional accuracy standard. Therefore, this study verifies the three-dimensional coordinates' accuracy from the UAV data. The objective was to assess the accuracy of the three-dimensional coordinates of the UAV map using theodolite survey data. The horizontal and vertical coordinates of the theodolite were obtained by closed-loop surveying and trigonometry, respectively, while the horizontal and vertical coordinates of the UAV were obtained from orthophotograph and the difference between the DSM and DTM data, respectively. The estimation of the accuracy of the three-dimensional coordinates consisted of the horizontal (X and Y) and vertical (Z) position accuracy. As a result, it was found that the RMSE of X and Y coordinates was 1.22 and 3.44, respectively, and the NSSDA standard error of horizontal accuracy was about 3.65 meters. On the other hand, The RMSE of Z value between the blueprint height and the theodolite measurement height was 1.19, and the NSSDA standard error of vertical accuracy was about 2.34 meters. The RMSE of Z value between the blueprint height and object height from the UAV was 4.19, and the NSSDA standard error was about 8.21 meters. In conclusion, the selection of horizontal position data was performed with either of the two survey methods depending on the acceptable accuracy. The ground survey data was high vertical positions more accurate than UAV. However, buildings with low heights (lower than 10 meters) can use both theodolite and UAV surveys.