Abstract
Abstract. Oblique images enable three-dimensional (3d) modelling of objects with vertical dimensions. Such imagery is nowadays systematically taken of cities and may easily become available. The documentation of cultural heritage can take advantage of these sources of information. Two new oblique camera systems are presented and characteristics of such images are summarized. A first example uses images of a new multi-camera system for the derivation of orthoimages, façade plots with photo texture, 3d scatter plots, and dynamic 3d models of a historic church. The applied methodology is based on automatically derived point clouds of high density. Each point will be supplemented with colour and other attributes. The problems experienced in these processes and the solutions to these problems are presented. The applied tools are a combination of professional tools, free software, and of own software developments. Special attention is given to the quality of input images. Investigations are carried out on edges in the images. The combination of oblique and nadir images enables new possibilities in the processing. The use of the near-infrared channel besides the red, green, and blue channel of the applied multispectral imagery is also of advantage. Vegetation close to the object of interest can easily be removed. A second example describes the modelling of a monument by means of a non-metric camera and a standard software package. The presented results regard achieved geometric accuracy and image quality. It is concluded that the use of oblique aerial images together with image-based processing methods yield new possibilities of economic and accurate documentation of tall monuments.
Highlights
The use of oblique photographs is as old as photogrammetry
Nowadays all imaging is digital and aerial imagery is taken from airplanes, helicopters, and unmanned aerial systems (UAS)
Cities are systematically photographed by means of such cameras and images of high quality are at disposal on the Internet
Summary
The use of oblique photographs is as old as photogrammetry. The famous cartoon where the Frenchman G.-F. Oblique images enable the recording of historical objects with a vertical extent. Such images are used for the production of 3d photorealistic models and façade plots as well as for the determination of the materials of which the object is built. Cities are systematically photographed by means of such cameras and images of high quality are at disposal on the Internet. This new possibility and the announcement of two new multi-camera systems started this investigation. The generation of 3d city models is a current task for photogrammetric companies and organizations Such tasks have similarities with the recording of cultural heritage. The characteristics of oblique images will be summarized and the experiences from two practical tasks will be presented and discussed
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