Link type
•Check Link type and click OK. Progress can be followed in the status bar.
•Analyses of river networks often describe the type of link a river reach represents. These are typically Interior, Exterior and Outlet. Different river patterns will have different ratios of these link types.
•The output of this process is a single text field called Link_Type containing either I for Interior, E for Exterior or O for Outlet.
•This process is influenced by the presence of pseudo nodes within the network. They will give a false impression on the number of types of links present in the network.
Pseudo nodes must be removed before processing the network for link type.
•Below is a series of images that explain how pseudo nodes affect the link type.
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A classic text book example showing 4 exterior links, 2 interior links and a single outlet |
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Displaying the same network with the nodes visible. Red nodes are pseudo nodes. |
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The addition of the pseudo nodes means there are 2 new interior links and what were exterior links now do not reach the confluence.
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•Before you remove the pseudo node consider why it was there in the first place? Is it a product of the way your data was collected? Do their presence mark the location of a boundary, for example a lakes edge? If so you would expect to see a pseudo node marking the outflow of the lake.
•A single polyline representing a small stream will be classified as an Exterior link.