Model Generalization of the Hydrography Network in the CARGEN Project - Advances in Cartography and GIScience - page 455

The generalization of braided sections of rivers needs further investigation,
as the first attempts did not produce satisfactory results. In one of our sam-
ple datasets the presence of too many flat edges inside braided sections of
rivers caused the river course reconstruction to fail; the only viable solu-
tion was then to exclude these sections from the pruning.

Source Generalized Length Density

River sections 9786 6290 2112 1474

River courses 5674 2530 2053 1091

Total length (meters) 3420245 2720324 299766 400155

Average length per section (meters) 349 432 142 366

Table 3: results of the generalization process; the third and fourth columns indicate
respectively the numbers relative to the rivers pruned by length and density thresholds.

Figure 9: results of the generalization: left source data, right generalized data (only re-
classified, not pruned).

This was achieved finding the cycles in the hydrography graph (the edges
forming a cycle are part of a braided stream). The braided parts of the
rivers then are not pruned but only re-classified. We are currently investi-
gating a generalization strategy that detects the areas enclosed between the
branches of a braided river and typifies the clusters of these areas either by
collapsing each area to a line, or by merging neighboring ones.

4- Conclusions and future plans

In this paper a complete process for model generalization of a hydro-
graphic network was described.