ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
Publications Copernicus
Articles | Volume X-4/W1-2022
13 Jan 2023
 | 13 Jan 2023


S. A. Fakhri, S. Motayyeb, M. Saadatseresht, H. Zakeri, and V. Mousavi

Keywords: UAVs, Spatial Resolution, Siemens Star Target, Ground Resolved Distance, Ground Sampling Distance, Point Spread Function

Abstract. In recent years, as the use of Unmanned Aerial Vehicle (UAV) imaging systems has increased, the photogrammetry community has conducted extensive research on the unique advantages of these systems. The UAVs are considered as one of the most important platforms for photogrammetry applications from various urban and non-urban areas at different scales. In UAV photogrammetry projects the spatial resolution of the images must be determined prior to the imaging stage. The spatial resolution of the images is a commonly-used criterion for detecting the smallest distance between two adjacent separable objects in the images. Numerous methods have been developed to precisely evaluate the spatial resolution of images. In this study, the Siemens star target, which is one of the most commonly used artificial targets for analysing spatial resolution was studied. The objective of this paper is to evaluate and compare the reduction of spatial resolution coefficient using the Siemens star target in images captured by UAVs. To this end, a method for automatically detecting the radius of the circle of ambiguity and calculating spatial resolution in UAV images has been developed. According to the findings of this study, the initial step in creating the Siemens star target, in terms of size and the number of acceptable arms, is dependent on the flying altitude of the UAV and the level of image blur. In addition, the reduction in spatial resolution of images captured by various UAVs varies, and its coefficient must be calculated for each project.