Principle, software and experiment of GPS-supported aerotriangulation

Abstract

In conventional aerial photogrammetry, the high accurate photogrammetric point determination is always carried out by aerotriangulation using a great deal of ground control points around the perimeter and in the center of block area because the exterior orientation parameters of aerial photographs are unknown. A technological revolution in photogrammetry has taken place since Navstar global positioning system (GPS) was applied to determine the 3D coordinates of exposure station positions during the photo flight missions. GPS-supported aerotriangulation is conducted by a combined bundle adjustment for photogrammetric observations and the camera orientation data. In this case, the essential ground control points are replaced by GPS-determined camera positions. Recent investigations show this method is coming to the practice. We have been engaged in the theoretical studies, soft-ware development, and related experiments and production in the field since 1990. So far the abundant research achievements are obtained in terms of the theory and application. In this paper, we first derives the mathematical model of GPS-supported aerotriangulation from the geometry between camera and airborne GPS antenna, then describes briefly a software package WuCAPS (Wuhan combined adjustment program system) developed newly by the author, which serves the purpose of the combined bundle adjustment for photogrammetric and non-photogrammetric observations. At the end of the present work, a set of actual aerial photographs, at the image scale of 1∶34 000, with airborne GPS data taken from Tianjing site, China were processed by WuCAPS. The empirical results have verified that the accuracy of the combined bundle adjustment with 4XYZ ground control points around the corners of block area is very close to that of the conventional bundle adjustment with 3 additional parameters, that leads to reduce 88% field survey and 75% production cost, and can meet the specification of topographic mapping at small or medium scale by GPS-supported aerotriangulation without ground control. This shows the ample applicability and the economic benefit of kinematic GPS relative positioning in high accurate photogrammetric point determination.