Abstract
Abstract. Unmanned Aerial Vehicles (UAVs) can be used to acquire highly accurate data in deformation survey, whereby low-cost digital cameras are commonly used in the UAV mapping. Thus, camera calibration is considered important in obtaining high-accuracy UAV mapping using low-cost digital cameras. The main focus of this study was to calibrate the UAV camera at different camera distances and check the measurement accuracy. The scope of this study included camera calibration in the laboratory and on the field, and the UAV image mapping accuracy assessment used calibration parameters of different camera distances. The camera distances used for the image calibration acquisition and mapping accuracy assessment were 1.5 metres in the laboratory, and 15 and 25 metres on the field using a Sony NEX6 digital camera. A large calibration field and a portable calibration frame were used as the tools for the camera calibration and for checking the accuracy of the measurement at different camera distances. Bundle adjustment concept was applied in Australis software to perform the camera calibration and accuracy assessment. The results showed that the camera distance at 25 metres is the optimum object distance as this is the best accuracy obtained from the laboratory as well as outdoor mapping. In conclusion, the camera calibration at several camera distances should be applied to acquire better accuracy in mapping and the best camera parameter for the UAV image mapping should be selected for highly accurate mapping measurement.
Highlights
Unmanned Aerial Vehicle (UAV) photogrammetry is different from close-range photogrammetry in their distance to the object (Kerle et al, 2008)
The results showed the relationship between image mapping accuracy and the camera parameters used
The camera parameter at 25-metre object distance was the optimum distance for the best mean accuracy for 1.5-metre and 25-metre image mapping
Summary
Unmanned Aerial Vehicle (UAV) photogrammetry is different from close-range photogrammetry in their distance to the object (Kerle et al, 2008). Camera calibration is considered important and needs to be studied to obtain highly accurate UAV mapping measurement using low-cost cameras. Research on camera calibration for long object distance has been done by Mohamed and Klaus-Peter (1999), Liu et al (2011), Pérez et al (2011), Rehak et al (2013), and Skaloud et al (2014). This study explores and extends the calibration of nonmetric cameras to several distances and the focus is more on the accuracy of the measurement between calibration parameters at three different UAV flying heights
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