Modelling three-dimensional objects (e.g. historical buildings) based on non-metric digital images is a complex task because the internal orientation and radial distortion parameters are unstable and unknown. In this paper, by analysing the mathematical basis of the central projection, the authors describe the feasibility of using the internal orientation of amateur photographs through the use of vanishing points (in a perspective drawing). The presented method is able to use zoomed photographs. Consequently, the paper also includes several ways of deriving the vanishing points analytically. The authors also propose a method for deriving the radial distortion parameters on the basis of the barrel/cushion effect. The advantage of this solution is the possibility to minimise the negative effects of the strong correlation between distortion parameters and the focal distance.

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