3D reconstruction plays an increasingly important role in modern photogrammetric systems. Conventional satellite or aerial-based remote sensing (RS) platforms can provide the necessary data sources for the 3D reconstruction of large-scale landforms and cities. Even with low-altitude UAVs (Unmanned Aerial Vehicles), 3D reconstruction in complicated situations, such as urban canyons and indoor scenes, is challenging due to the frequent tracking failures between camera frames and high data collection costs. Recently, spherical images have been extensively exploited due to the capability of recording surrounding environments from one camera exposure. Classical 3D reconstruction pipelines, however, cannot be used for spherical images. Besides, there exist few software packages for 3D reconstruction of spherical images. Based on the imaging geometry of spherical cameras, this study investigates the algorithms for the relative orientation using spherical correspondences, absolute orientation using 3D correspondences between scene and spherical points, and the cost functions for BA (bundle adjustment) optimization. In addition, an incremental SfM (Structure from Motion) workflow has been proposed for spherical images using the above-mentioned algorithms. The proposed solution is finally verified by using three spherical datasets captured by both consumer-grade and professional spherical cameras. The results demonstrate that the proposed SfM workflow can achieve the successful 3D reconstruction of complex scenes and provide useful clues for the implementation in open-source software packages. The source code of the designed SfM workflow would be made publicly available.

翻译：三维重建在现代摄影测量系统中发挥着日益重要的作用。传统的卫星或航空遥感平台可为大规模地形与城市的三维重建提供必要的数据源。即便使用低空无人机，在城市峡谷、室内场景等复杂环境下，由于相机帧间跟踪频繁失败且数据采集成本高昂，三维重建仍面临挑战。近年来，球面图像因其单次曝光即可记录周围环境的特性而得到广泛应用。然而，经典的三维重建流程无法直接用于球面图像。此外，针对球面图像的三维重建软件包也较为匮乏。本研究基于球面相机的成像几何，深入探讨了利用球面对应点进行相对定向、利用场景与球面点间的三维对应点进行绝对定向的算法，以及光束法平差优化的代价函数。同时，结合上述算法，提出了一套适用于球面图像的增量式运动恢复结构工作流程。最后，采用消费级与专业级球面相机采集的三组球面数据集对所提方案进行了验证。结果表明，所提出的运动恢复结构工作流能够成功实现复杂场景的三维重建，并为相关开源软件包的实现提供了有益参考。该工作流的设计源代码将公开提供。