Using the Straight Skeleton for Generalisation in a Multiple Representation Environment

In recent time a lot of research has been done towards the comprehensive administration of geographic data of different scales and thematic domains. A promising approach is the use of a Multiple Representation Database (MRDB) in which links between corresponding objects are explicitly modelled. The advantage of this approach is a limitation of redundancies and inconsistencies. It can be expected that this comprehensive administration of different data sets supports complex analysis and eases the updating process (Sester et al. 1998). Our aim is to build up a framework enabling the automatic update of features in an MRDB. We envision a system which is able to propagate information into the other representations in the database when a feature is added to an arbitrary level. To meet this demand algorithms are needed which are able to perform the generalisation of the added data considering the embedding context. The algorithms needed for generalisation depend on the relationships between objects in adjacent scale levels. The main relation is the aggregation, however, there are also more complex ones. Two of these cases are area collapses and geometry type changes. This also includes partial geometry type changes. The paper is organized as follows: after a review of related work, the relationships between objects in different scales are briefly analyzed in section 2. The main focus of the paper lies, however, in the presentation of a skeleton algorithm that can be applied to solve this task for the generalisation cases area collapse and geometry type changes from area to line. In this work the Straight Skeleton is used. The algorithm and its application to generalisation is presented in section 3. In section 4 first ideas are presented how this generalisation method can be used for the propagation of updates in MRDB. A summary concludes the paper.

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