AUTOMATIC EXTERIOR ORIENTATION PROCEDURE FOR LOW-COST UAV PHOTOGRAMMETRY USING VIDEO IMAGE TRACKING TECHNIQUE AND GPS INFORMATION

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 XXII ISPRS Congress, 25 August – 01 September 2012, Melbourne, Australia AUTOMATIC EXTERIOR ORIENTATION PROCEDURE FOR LOW-COST UAV PHOTOGRAMMETRY USING VIDEO IMAGE TRACKING TECHNIQUE AND GPS INFORMATION T. Anai a, *, T. Sasaki a, K. Osaragi a, M. Yamada a. F. Otomo a, H. Otani b a R&D Center, TOPCON CORPORATION, 75-1, Hasunuma, Itabashi, Tokyo – b Positioning Business Unit, TOPCON CORPORATION, 75-1, Hasunuma, Itabashi, Tokyo Commission V, ICWG V/I KEY WORDS: Automation, Exterior Orientation, Matching, Video, Tracking, GPS, Robust ABSTRACT: In this paper, we propose the automatic exterior orientation procedure for the Low-cost Unmanned Aerial Vehicle (UAV) photogrammetry. The Low-cost UAV has become useful tool for low altitude photogrammetry from the rapidly increasing of automatic control technique in past several years. However, automatic exterior orientation is still important issue. The most important point of automatic exterior orientation is the automatic detection of corresponding points in each still image. For this goal, the authors have developed the automatic corresponding point detection technique using both video Image and still images. The video image of this investigation is obtained with still images simultaneously. Therefore, the tracking result of video image gives robust correspondence information between each still image. Moreover, the exterior orientation procedure using GPS information from UAV and minimum ground control points have been investigated. This paper is structured as follows. At the first we describe the over view of automatic exterior orientation procedure in this investigation. As the next, the details of tracking of common feature points and robust bundle adjustment are described. Also, accuracy assessment of this automatic exterior orientation procedure is described. Finally some conclusion is given. corresponding point between each still image has to be performed by image based approach. The automatic detection of corresponding points using coded target is one of the popular approaches. However, the photogrammetry using Low-cost UAV is often used under the difficult situation for direct ground surveying such as disaster area or cultural heritage. Consequently, only minimum targets can locate in area of interest, but the correspondence of all images is not provided by these targets. Another important problem is the robust exterior orientation using automatic detected corresponding points, GPS information at waypoints from UAV, minimum ground control points (GCP). Because the corresponding points from common feature are often including error and also the positioning information from Low-cost UAV often includes outlier, robust exterior orientation has to be investigated. On the other hand, the authors have been concentrating to investigate the Structure from Motion (SfM) technique using both video image and GPS in late years (Anai, 2010). In these investigations, we have proposed the robust feature point tracking method based on the “Orientation Code” (OC) image processing (Ullah 2001). Also, bundle adjustment method for video image that uses both SfM technique and GPS data with considering error in GPS observation. If both video image and still images are obtained from UAV, the tracking information of video image gives the robust corresponding information between each still image. From these circumstances mentioned above, this paper proposes about automatic corresponding point detection method using both video images and high resolution still images. Also, the automatic exterior orientation procedure using corresponding points, GPS and minimum GCP is also described. 1. INTRODUCTION The aerial triangulation in photogrammetry using mass images taken by the Low-cost UAV has become possible easily by rapidly increasing of automatic flight control technique of Lowcost UAV in These past several years. The Low-cost UAV which integrated GPS and IMU usually has ability to perform autonomous flight and automatic navigation along planned waypoints. These waypoints are usually planned beforehand easily by dedicated software as considering the camera parameter, area of interest, overlap of image, altitude and so on. Moreover, still images at planned waypoints are acquired automatically by digital still camera mounted on UAV. Therefore, Low-cost UAV system is widely used as the useful platform in the low altitude application field of photogrammetry such as agriculture, archaeology, traffic monitoring, and disaster area surveying (Remondino, 2011). However, in order to perform the fully automatic aerial triangulation using mass still image in low altitude application field, some problems have to be resolved. The automatic detection of corresponding point from common features visible in each still image is the most important problem. In the case of low altitude application using UAV, this problem becomes complex issue because the geometry of images is similarly to close-range photogrammetry. In the case of standard altitude application of automatic aerial triangulation, direct geo-referencing approach using GPS and IMU on UAV is often considered. But, direct geo-referencing approach using GPS and IMU on Low-cost UAV is difficult in the case of low altitude application because the GPS observation is more affected by environment than standard case of aerial triangulation. Therefore, the automatic detection of * Corresponding author. 469 International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 XXII ISPRS Congress, 25 August – 01 September 2012, Melbourne, Australia 2. AUTOMATIC EXTERIOR ORIENTATION USING VIDEO IMAGE AND STILL IMAGES 2.2 Flow of Automatic Exterior Orientation procedure Figure 2 shows the flow of automatic exterior orientation procedure in this investigation. The waypoint planning and flight control are performed by “AscTec autopilot control software” provided by Ascending Technologies GmbH. High resolution still images at waypoints, video image during flight, and also positioning information of each waypoint are obtained as the result of a flight. At the first of this processing, the detection of common feature points from high resolution still image and tracking of detected feature points on video image sequences are performed using robust feature point tracking method based on the OC image processing. The tracking result of feature points are obtained in the image coordinate on high resolution still image. As the next step, sub-pixel matching of each feature point is performed. The good results of this subpixel matching are used as candidate of correct pass points. In order to perform tie point matching, the exterior orientation using these candidate pass points is performed. The result of exterior orientation in this step gives the geometry of ca (...truncated)