Geoscience Reference
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neither be translated in deleting all the dangling edges shorter than 250
meters, as this will much probably result in the entire graph to shrink.
Figure 5:
relations between rivers: a and b are siblings, and they are both father of c, that
is a child of both a and b; d and e are children of c.
The IGMI specifications also require pruning the network of the least im-
portant branches in dense regions. This implies the ability to recognize the
importance of each river and compare it. The four different classes of the
IGMI data model are not enough for such a task: a new classification is
needed, that could take in account other parameters to evaluate the impor-
tance of each river.
The solution was to set up a network pruning algorithm able to reconstruct
the course of each river, to enrich the data in order to classify the rivers by
importance and to prune the network, first applying the length threshold
and after removing the least important branches in the densest regions of it.
All these considerations lead us to develop a pruning algorithm that fol-
lows these steps:
1.
reconstruction of flow direction,
2.
data enrichment,
3.
river course reconstruction,
4.
short rivers pruning,
5.
dense rivers pruning.
2.3.1 Reconstruction of flow direction
The first step to reconstruct the course of a river from its sections is to
know the direction that water is flowing to.
