Extracting the pseudo nodes of a network

• RivEX is capable of identifying the pseudo nodes of network.  These are nodes where only 2 polylines join thus having a valency of 2.  The image below shows an example network with the node valency adjacent to the node.  As you can see there is a range of 1 to 3.

• Pseudo nodes influence link identification as their presence alters the topology of the network. So you would want to create a pseudo node free network before attempting to identify the type of link a polyline is (see below).

• If you looked at only the polylines of your river network then the pseudo node is often irrelevant when considering stretches of river between confluences.   They are part of the computer network structure and not a real feature.  So in some cases you may want to remove them.

• Select the layer, polyline ID and node fields.

• Tick the "Identify Pseudo Nodes" check box and and click on Go!

• The output is a Shapefile with just the pseudo nodes and is stored in C:\RivEX\Output.  The new file ends with the suffix "_Pseudo_Nodes".  Included in the attribute table of this Shapefile are the node ID numbers and  XY coordinates.  Using the example image above the output would be the points in the image below.

• Before removing pseudo nodes consider why it was there in the first place.  Is it an artefact of the way the network was captured or does it represent a real world feature such as the inflow/outflow of a lake?