Generalizing drainages with density differences based on river length and the amount of tributaries

摘要

Drainage generalization is a process of information abstraction, aiming to derive a coarser dataset from original detailed one. The difficulties lie in selectively omitting some rivers while maintaining the overall characteristics of the drainages. This paper took use of the amount of the tributaries of individual rivers to evaluation their relative importance in the drainage, and the contribution to the preservation of the drainage pattern. That is, the rivers having more tributaries are more important than those having fewer tributaries; at the same time, the differences of the amount of the tributaries of the rivers may indicate the density differences of their sub-drainages. In view of the important role of river length and hierarchical level in manual generalization, we combined river length, hierarchical level and the amount of the tributaries to evaluate rivers. The three indexes were computed, and then integrated as a complex index for every river, on the basis of constructing a river tree of the drainage. A case study of drainage generalization shows that the complex index is effective to reflect the relative importance of the rivers in the drainage, and can be used to maintain the density differences of the drainage in map generalization.