A New Modelling Technique for Object-oriented Photogrammetric Computer Vision Algorithms

Photogrammetric Computer Vision algorithms often deal with complex numerical calculations and complex data structures. For modelling the numerical calculations usually a mathematical model is used. For the data structures an Object-Oriented model is appropriate. But there is still a lack in modelling the combination of both kinds of notation. In this paper we present a new modelling technique for presenting mathematical and object-oriented aspects in one model. This modelling technique is based on the Unified Modelling Language (UML) and optimally suited for algorithms with complex numerical models and data models. For the semantics of class members in the UML model we use a formal description of constraints, which is similar to the Object Constraint Language (OCL) included in the UML specification. Since OCL is not capable of complex mathematical expressions, we enhance this notation to handle mathematics, and we name it OCL+M. We show, that typical problems in photogrammetry can be modelled by using an object-oriented model with OCL+M. The advantages of this modelling technique are: 1. A clear presentation of the mathematical model within the object-oriented model, 2. The methods of the classes are easy to implement, 3. The implementation is straightforward and maintainable and 4. The model can be tested with little efforts. * Corresponding author.