Institute of Photogrammetry and Remote Sensing, Helsinki University of Technology, P.O. Box 1200, FI-02015 TKK, Finland; E-Mails:
Sensors (Basel). 2009;9(8):6008-27. doi: 10.3390/s90806008. Epub 2009 Jul 29.
Comprehensive 3D modeling of our environment requires integration of terrestrial and airborne data, which is collected, preferably, using laser scanning and photogrammetric methods. However, integration of these multi-source data requires accurate relative orientations. In this article, two methods for solving relative orientation problems are presented. The first method includes registration by minimizing the distances between of an airborne laser point cloud and a 3D model. The 3D model was derived from photogrammetric measurements and terrestrial laser scanning points. The first method was used as a reference and for validation. Having completed registration in the object space, the relative orientation between images and laser point cloud is known. The second method utilizes an interactive orientation method between a multi-scale image block and a laser point cloud. The multi-scale image block includes both aerial and terrestrial images. Experiments with the multi-scale image block revealed that the accuracy of a relative orientation increased when more images were included in the block. The orientations of the first and second methods were compared. The comparison showed that correct rotations were the most difficult to detect accurately by using the interactive method. Because the interactive method forces laser scanning data to fit with the images, inaccurate rotations cause corresponding shifts to image positions. However, in a test case, in which the orientation differences included only shifts, the interactive method could solve the relative orientation of an aerial image and airborne laser scanning data repeatedly within a couple of centimeters.
要全面建立我们环境的三维模型，需要整合地面和航空数据，这些数据最好通过激光扫描和摄影测量方法来采集。然而，这些多源数据的整合需要精确的相对定向。本文提出了两种解决相对定向问题的方法。第一种方法包括通过最小化航空激光点云和三维模型之间的距离来进行配准。三维模型由摄影测量测量和地面激光扫描点生成。第一种方法用作参考和验证。在完成物方配准后，就知道了图像和激光点云之间的相对定向。第二种方法利用多尺度图像块和激光点云之间的交互式定向方法。多尺度图像块包括航空图像和地面图像。多尺度图像块的实验表明，当更多的图像包含在块中时，相对定向的精度会提高。比较了第一和第二种方法的定向结果。比较结果表明，使用交互式方法很难准确检测到正确的旋转。因为交互式方法迫使激光扫描数据与图像匹配，所以不准确的旋转会导致图像位置相应地移动。然而，在一个测试案例中，其中定向差异仅包括位移，交互式方法可以在几厘米的范围内重复解决航空图像和航空激光扫描数据的相对定向问题。
