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An Experimental Study on Assessing Precision and Accuracy of Low-cost UAV-based Photogrammetry

저가형 UAV 사진측량의 정밀도 및 정확도 분석 실험에 관한 연구

  • Yun, Seonghyeon (Dept. of Eco-friendly Offshore Plant FEED Engineering, Changwon Natioanl University) ;
  • Lee, Hungkyu (Dept. of Civil Engineering, Changwon National University) ;
  • Choi, Woonggyu (Dept. of Global Smart City, Sungkyunkwan University) ;
  • Jeong, Woochul (Dept. of Civil Engineering, Changwon National University) ;
  • Jo, Eonjeong (Dept. of Civil Engineering, Changwon National University)
  • Received : 2022.06.07
  • Accepted : 2022.06.15
  • Published : 2022.06.30

Abstract

This research has been focused on accessing precision and accuracy of UAV (Unmanned Aerial Vehicle)-derived 3-D surveying coordinates. To this end, a highly precise and accurate testing control network had been established by GNSS (Global Navigation Satellite Systems) campaign and its network adjustment. The coordinates of the ground control points and the check points were estimated within 1cm accuracy for 95% of the confidence level. FC330 camera mounted on DJI Phantom 4 repeatedly took aerial photos of an experimental area seven times, and then processed them by two widely used software packages. To evaluate the precision and accuracy of the aerial surveys, 3-D coordinates of the ten check points which automatically extracted by software were compared with GNSS solutions. For the 95% confidence level, the standard deviation of two software's result is within 1cm, 2cm, and 4cm for the north-south, east-west, and height direction, and RMSE (Root Mean Square Error) is within 9cm and 8cm for the horizontal, vertical component, respectively. The interest is that the standard deviation is much smaller than RMSE. The F-ratio test was performed to confirm the statistical difference between the two software processing results. For the standard deviation and RMSE of most positional components, exception of RMSE of the height, the null hypothesis of the one-tailed tests was rejected. It indicates that the result of UAV photogrammetry can be different statistically based on the processing software.

저가형 UAV기반 사진측량의 정밀도와 정확도를 평가하기 위한 실험을 수행하였다. 높은 정확도의 지상기준점과 검사점의 3차원 좌표를 추정하고자 GNSS정지관측과 기선해석, 망조정을 수행하였고, 신뢰수준 95%에 대하여 정확도가 1cm 이내인 좌표를 확보하였다. 실험 대상지에 대한 항공 사진은 DJI Phantom 4와 이에 탑재된 FC330 카메라로 7회 반복 촬영하였고, 이를 두 가지 소프트웨어로 처리하였다. 10개 검사점에 대한 소프트웨어 자동 추출좌표와 GNSS 추정해를 비교하여 표준편차 및 RMSE를 분석하였다. 두 소프트웨어 처리 결과, 95% 신뢰수준에 대해 표준편차는 남북, 동서, 높이 방향 각각 약 1cm, 2cm, 4cm 이내, RMSE는 수평과 높이 각각 9cm, 8cm 이내였으며, 표준편차가 RMSE에 비해 현저히 작았다. 두 소프트웨어 처리 결과의 통계적 차이를 확인하고자 F-ratio 검정을 수행하였다. 정밀도에 대해서는 모든 좌표 성분에 대해 한쪽꼬리 검정의 귀무가설이 기각되었고, RMSE에 대해서는 수평에 대한 것만 기각되었다. 이에 따라, 동일한 사진 자료를 처리하더라도 소프트웨어에 따라 그 결과에 통계적 차이가 있을 수 있음에 유의할 필요가 있다.

Keywords

Acknowledgement

본 연구는 2021년도 교육부의 재원으로 한국연구재단의 지원을 일부 받아 수행된 지자체-대학 협력기반 지역혁신 사업의 결과입니다.(NTIS 과제고유번호: 1345341781, NRF 과제관리번호: 2021RIS-003)

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