Analyzing the Impact of Calibration Parameters on Ground Control Point’s Error Ellipses in Orthophotos

Abstract

Orthophoto accuracy is strongly influenced by camera calibration parameters and the spatial distribution of Ground Control Points (GCPs). However, the interaction between these factors remains insufficiently explored, especially using spatial error representations such as error ellipses. This study addresses that gap by analyzing how intrinsic camera parameters affect spatial accuracy in relation to varied GCP configurations. Aerial data were collected over twelve sample locations within the Indonesian University of Education campus. Positional errors were evaluated through two- and three-dimensional error ellipses, with correlation analyses performed between maximum GCP errors and individual calibration parameters. The results reveal prosibilities of correlations between calibration quality and error magnitude. High focal length stability and minimal principal point offset were associated with lower errors, while increased radial and tangential distortion often led to spatial inaccuracy. Anomalies were observed, highlighting the sensitivity of orthophoto precision to calibration deviations and poor GCP layouts.  Correlation analysis revealed that a deviation of >50 pixels in the principal point coordinate is associated with an increase of up to 35 cm in spatial error This study emphasizes the importance of stable calibration and optimal GCP distribution in minimizing positional uncertainty.