True Orthoimage Generation in Close Range Photogrammetry

Digital orthoimage compose an efficient and economic way for the representation of two-dimensional texture information. This kind of information is functional when the user has to evaluate, analyze or measure the objects presented in the image. If the projection has to be performed on a single plane and the form of the object is not rough, the process is simple and well-known as simple rectification. The orthoimage production of rough objects is still an on-going problem especially in close-range applications (for example architectural or archaeological applications) where the major problem is that of the complication of the description of the analytical shape of the object. In most of the cases the points with identical XY co-ordinates display different heights. Regular grids are the most established solutions used to build-up a mathematical shape description of an object. In this way a conventional orthophoto cannot provide the ultimate representation of the object through the rectification process. In the last few years a novel expression, the «true orthoimage» raised to describe the ideal illustration of the object through the rectification development. This paper is a contribution on the research for the true orthoimages. The on-going study focuses on the description and test of a solution which uses a 3D model for the creation of a true orthoimage in close range photogrammetric applications.