Yung-Chuan Chen
1*, Po-Chin Tsai
2, Ping-Chuan Wang
2, Yi-Hsing Tseng
3Abstract
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
1 Lecturer, Department of Construction Science and Engineering, De-Lin Institute of Technology.
2 Master, Department of Geomatics, National Cheng Kung University.
3 Professor, Department of Geomatics, National Cheng Kung University.
Corresponding Author, TEL: 886-2-22733567#376, E-mail: [email protected].
陳永泉、蔡博慶、王彬權、曾義星：可攜式全景影像測繪系統之設計與光束法平差
the coordinate differences is better than 3cm, 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 1cm, 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.
Keyword: Bundle adjustment, Mobile mapping system, Panoramic image, Photogrammetry, Portable
國土測繪與空間資訊 第二卷第一期
一、前言
空間定位及導航科技與數位攝影測量技術的整合，形成各式空載、車載或人員 攜帶之移動式測繪系統(Mobile Mapping System) ，帶動了移動測繪科技的研究與發 展，大幅提升了空間資料獲取及測繪的效率。目前所發展的移動式測繪系統以車載 系統，例如 Backpack Mobile Mapping System (Ellum, 2001)或 Point Grey 的 Ladybug 全景相機，應可結合精密定位及定方位技術，提升現場觀測的效率，有利於艱困環 境的應用。然而如何簡化可攜式系統的配備達到輕便攜帶，但又能達到高效率觀測 及定位定方位的要求，尚有待研究發展。
針對可攜式系統的訴求，本研究提出一套輕便又能達到高效率觀測及定位定方 位的觀測系統，稱為可攜式全景影像測繪系統(Portable Panoramic Image Mapping System, PPIMS)。PPIMS 配備六部高解析度單眼相機，以環狀的排列的方式固定於 平台，平台上設置同時曝光機制，使得六幅同時成像的影像可構成環場全景影像。
陳永泉、蔡博慶、王彬權、曾義星：可攜式全景影像測繪系統之設計與光束法平差
型測繪系統無法運達之測區，提供另一種測繪方法的選擇，並期待能與車載或空載 測繪系統互相輔助以獲得更完整之空間資訊。