Creating nodes and node ID fields

• RivEX can create and populate the node fields required by the stream ordering algorithms.

• You can also write the nodes to a separate Shapefile which will be stored in C:\RivEX\Output.

• RivEX does not overwrite any existing node fields; it will always create new fields named FnodeX  and TnodeX  where X  is an incremental number.  This is done in case other data references the old ID numbers.

Building node fields for the first time

• If your river network is simply a collection of polylines with nothing more than a unique ID number for each polyline then you must build the From-node and To-node fields.

• When building the data dictionaries, the only option available to you for the node fields is  *** ? *** as shown below.

• You will then be warned with the following message box and only the update attribute table check box is enabled.

• Click Go! and RivEX will process your network, creating two new fields Fnode and Tnode.

Rebuilding node ID fields and saving the nodes to a separate Shapefile

• You may have edited the network in someway which will require RivEX to compute new node ID numbers.  Remember RivEX does not overwrite old fields but simply creates two new fields.

• To build the nodes you must select the layer, polyline ID and old node fields.  RivEX does not actually use the old node fields, this is simply a requirement of the build data dictionaries process.

• If your network does not have a field containing unique polyline ID numbers then click here to find out how to create this.

• Simply tick the "Update attribute table" and/or "Create a node layer" and click on Go!

• Below is an image of a section of river with the nodes and their ID numbers.

• Below are the attribute tables of a network and its node layer. For each node extracted, the XY coordinates, valency and type are stored within the new node attribute table.

• Valency is the number of polylines connected to the node.

• RivEX can identify up to six types of nodes and labels them with a single character code field called Node_Type.  The codes are: