Absolute and Exterior Orientation Using Linear Features

For many years we have had digital photogrammetric systems available that can perform automatic interior and relative orientation of aerial photographs. Developments in absolute and exterior orientation are not so robust because the problem is significantly more difficult. The reason for the increase in difficulty is that there is no easy way to create the master image or target patch which represents the traditional ground control point. If we have such an image then there are a number of techniques that are well established to undertake area or feature based matching to find the corresponding point on the photograph. There are also an increasing number of users of photogrammetric techniques and software who would like to be able to provide control for absolute or exterior orientation in a very easy and efficient way without having to rely on careful identification of ground control points. These two issues have been the motivation to investigate the general issue of improving the flexibility and ease of providing ground control for the processes of absolute and exterior orientation using analytical and digital techniques. This paper will present a new approach to absolute and exterior orientation based on the measurement of linear features and their automatic matching. The results show that the technique can produce results suitable for many environmental mapping applications and in some instances is suitable for topographic mapping. It is also shown to have the capability of automatic relative orientation.