This thesis concerns object oriented modelling and automatic generalisation of geographic information. The focus however is not on traditional paper maps, but on screen maps that are automatically generated from a geographical database. Object oriented modelling is used to design screen maps that are equipped with methods that automatically extracts information from a geographical database, generalises the information and displays it on a screen. The thesis consists of three parts: a theoretical background, an object oriented model that incorporates automatic generalisation of geographic information and a case study where parts of the model have been implemented.
An object oriented model is an abstraction of reality for a certain purpose. The theoretical background describes different aspects that have impact on how an object oriented model shall be designed for automatic generalisation. The following topics are described: category theory, the human ability to recognise visual patterns, previous work in automatic cartographic generalisation, and object oriented modelling.
A view is here defined to consist of several static levels, or maps, defined at different resolutions. As the user zooms the level that is appropriate for the particular resolution is shown. An object class belongs to one and only one level and has a certain symbolisation. The automatic creation of new objects in a level is discussed as well as the relation between objects in different levels. To preserve topological relations between objects in a level a network structure is formed between all linear objects in a level and objects that might cause conflicts are modelled using dependencies.
The model is designed for a set of typical geographical object classes such as road, railroad, lake, river, stream, building, built-up area etc. The model is designed to handle information in a scale-range from 1:10 000 to 1:100 000. The model has been implemented for a subset of these classes and tested for an area covering approximatley 60 km2.
Institutionen för geodesi och fotogrammetri , 2001. , 103 p.
Digital cartography, automatic cartographic generalization, object oriented modeling