Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography (한국측량학회지)

Korean Society of Surveying, Geodesy, Photogrammetry and Cartography (한국측량학회)
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Orientation Analysis between UAV Video and Photos for 3D Measurement of Bridges

교량의 3차원 측정을 위한 UAV 비디오와 사진의 표정 분석

  • Han, Dongyeob (Dept. of Marine and Civil Engineering, Chonnam National University) ;
  • Park, Jae Bong (Research Institute for Infrastructure Performance, KISTEC) ;
  • Huh, Jungwon (Dept. of Marine and Civil Engineering, Chonnam National University)
  • Received : 2018.09.18
  • Accepted : 2018.11.18
  • Published : 2018.12.31
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Abstract

UAVs (Unmanned Aerial Vehicles) are widely used for maintenance and monitoring of facilities. It is necessary to acquire a high-resolution image for evaluating the appearance state of the facility in safety inspection. In addition, it is essential to acquire the video data in order to acquire data over a wide area rapidly. In general, since video data does not include position information, it is difficult to analyze the actual size of the inspection object quantitatively. In this study, we evaluated the utilization of 3D point cloud data of bridges using a matching between video frames and reference photos. The drones were used to acquire video and photographs. And exterior orientations of the video frames were generated through feature point matching with reference photos. Experimental results showed that the accuracy of the video frame data is similar to that of the reference photos. Furthermore, the point cloud data generated by using video frames represented the shape and size of bridges with usable accuracy. If the stability of the product is verified through the matching test of various conditions in the future, it is expected that the video-based facility modeling and inspection will be effectively conducted.

시설물의 유지 관리 및 모니터링에 UAVs (Unmanned Aerial Vehicles)의 활용이 확대되고 있다. 안전 점검을 위한 시설물의 외관 상태 평가를 위하여 고해상도 영상을 취득하는 것이 필요하며, 넓은 지역을 빠르게 취득하기 위하여 비디오 데이터로 취득할 필요가 있다. 일반적으로 비디오 데이터에는 위치 정보가 포함되지 않아, 검사 개체의 실제 크기에 대한 정량적 분석이 어렵다. 본 연구에서는 교량 시설물을 대상으로 비디오 프레임과 기준 사진의 정합을 이용하여 교량의 3차원 점군(point cloud) 데이터의 활용성을 평가하고자 한다. 드론을 이용하여 비디오와 사진을 취득하고, 기준 사진과의 특징점 정합을 통하여 비디오 프레임의 외부 표정 요소를 생성하였다. 실험 결과 비디오 프레임 데이터는 기준 사진과 유사한 표정 정확도를 얻었으며, 표정된 프레임 데이터를 이용하여 생성된 점군 데이터는 교량의 형상 및 크기를 잘 표현하였다. 향후 다양한 조건의 정합 실험을 통하여 결과물의 안정성이 확인되면, 비디오 기반의 시설물 모델링 및 점검에 효과적으로 적용될 것으로 기대된다.

Keywords

GCRHBD_2018_v36n6_451_f0001.png 이미지

Fig. 1. Lateral view of the bridge pier

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Fig. 2. Some images obtained by the Phantom 4 Pro V2; (a) Photos (b) Video frames

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Fig. 3. (a) Masked sample images (b) masked enhanced sample images

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Fig. 4. Distance difference of a pier’s photo point clouds and point clouds generated from (a) original frames (b) masked frames (c) masked enhanced frames. The green points have relatively high distance differences

GCRHBD_2018_v36n6_451_f0005.png 이미지

Fig. 5. DSM of the pier using (a) photos (b) original frames (c) masked frames (d) masked enhanced frames

Table 1. Phantom 4 pro V2 specification

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Table 2. Features matching with photos

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Table 3. Errors of exterior orientation

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Table 4. Accuracy assessment of a point cloud from video frames with reference to photos’ point clouds (unit: meter)

GCRHBD_2018_v36n6_451_t0004.png 이미지

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