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可攜式全景影像測繪系統之設計及光束法平差

The Design and Bundle Adjustment of a Portable Panoramic Image Mapping System

Abstracts


車載移動式測繪系統結合導航定位及光學感測器,大幅提升了空間資料獲取及測繪的效率,能夠進行大範圍的空間資料蒐集。人員攜帶式移動式測繪系統具有輕便攜帶、容易施測、且價位低等好處,有利於車載系統無法進入或艱困環境等區域的應用。針對如道路周邊外之場景、災害現場、橋梁河道設施、或山區林地等,本文提出一套輕便又能達到高效率觀測及定位的可攜式全景影像測繪系統,得以快速擷取三維空間資訊。此系統結合六台數位單眼相機及GPS接收儀於一個方便攜帶及操作的六角形平台,六部相機以環形排列固定於平台以獲取環景影像,並以GPS進行平台之定位。所有相機皆經過內方位率定,並以具有四周佈滿標點的室內率定場,率定六部相機之相對位置及方位關係,再應用一個室外率定場求平台中心位置與六部相機之相對位置關係。在應用上,本系統可在不使用控制點的情況下達成多測站平台方位解算,並換算得每張影像的外方位元素以進行物空間點位測繪。平台方位解算是利用不同拍攝站間影像的連結點及平台中心位置觀測量,以相機與平台中心的相對位置及方位關係為約制條件,進行光束法平差,解算各測站之平台方位。實驗結果顯示,本系統可成功以多測站無控制點的情況下達成平台方位解算,以檢核點檢驗測繪點位,顯示各坐標差值的RMSD都在3公分以內,唯Y坐標有約6公分的系統性偏差。但加入少數控制點即可明顯改善系統性偏差,使得三軸坐標的平均偏差量皆小於1公分,各坐標差值的RMSD都在0.5公分以內。顯示加入控制點可大幅改善測站方位解算的誤差,提升定位之精度。本文亦應用此系統於房屋三維模型的測繪,展示場景實物測繪的實用性及方便性。

Parallel abstracts


The car-based mobile mapping systems (MMSs) are usually equipped with the navigation systems and the image sensors. These car-based systems can be used to gather the spatial information and to generate the maps efficiently, and they can be applied to collecting the spatial information of large areas. However, the portable mobile mapping systems have a lot of advantages, such as convenience of portability, versatility of mapping, and low cost. These portable systems can be used in remote areas that can't be accessed by car-based MMSs. This paper proposes a Portable Panoramic Image Mapping System (PPIMS) which can be used to collect 3D spatial information quickly. The PPIMS is not very heavy to carry, and it is also very efficient for mapping and positioning. This system can be applied to mapping of remote areas, disaster areas, mountains and forest areas. The PPIMS is equipped with six cameras, a GPS receiver and a platform. The platform is very easy to carry and operate. The six cameras are rigidly mounted on the platform to capture panoramic images, and the GPS can provide the position information of the platform. The interior orientation of each camera has been calibrated in advance, and then the relative position and orientation relationship between cameras has been calibrated in an indoor calibration field where hundreds of photogrammetric targets are well distributed along the walls, ceiling, and floor. Finally, the relative position relationship between the platform center and the six cameras are calibrated in an outdoor calibration field. The platform orientations of the stations can be calculated even without any control point, and then the exterior orientation elements of each image can be determined. Following this, the coordinates of the object points can be computed using the intersection method. The bundle adjustment procedure for the PPIMS is used to figure out the platform orientation. In this procedure, the observations include the image coordinates of the tie points and the coordinates of the platform center of different stations. Therefore, the relative position and orientation relationship between the cameras and the GPS are constraint conditions. According to the experimental results, the platform orientation of the stations can be calculated successfully even without any control point. Using the check points to evaluate the positioning accuracy, the RMSD of the coordinate differences is better than 3 cm, but the systematic error of Y coordinate is about 6 cm. On the other hand, when three control points are used, the systematic error can be improved, the average coordinate difference is not greater than 1 cm, and the RMSD of each coordinate difference is always better than 0.5 cm. Using only a few control points, the precision of station orientation is better, and the accuracies of positioning also can be improved significantly. The PPIMS is also used to generate a 3D building model, thus the versatility and convenience of this equipment has been demonstrated in this experiment.

References


王彬權,2012,《可攜式全景影像測繪系統之系統率定》,國立成功大學測量及空間資訊學系碩士論文。
Ellum, C. M., 2001, The development of a backpack mobile mapping system, UCGE Report NO. 20101, Department of Geomatics Engineering, University of Calgary.

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