Create a node layer

Summary :: Usage :: Parameters :: Outputs :: Warnings :: Limitations :: Code sample

Summary

This tool can extract out specific nodes by their type and store them in the RivEX output folder.

Usage

This tool can extract out specific nodes by their type and store them in the RivEX output folder. Any selection on the input river network is cleared before extraction runs. You can extract 4 types of layers:

Layer	Description
Mouth	Only mouth nodes are extracted
Source	Only source nodes are extracted
Pseudo	Only Pseudo nodes are extracted
All Nodes	All nodes are extracted along with their type and valency

Nodes

An example of the node dataset labelled by NodeID.

If tool is run within ArcPro then output is automatically added to the map.

Parameters

Name

Help

Data type

River Network

The river network. For best results the network should be within a File GeoDatabase

Feature Layer

Node type

The type of node you wish to extract from the network

Mouth nodes - Only mouth nodes are extracted
Source nodes - Only source nodes are extracted
Pseudo nodes - Only pseudo nodes are extracted
All nodes - All nodes are extracted along with their type and valency

String

Outputs

The All nodes option will also include a node valency field and a text field identifying type of node. Valency is the number of lines connecting to the node, the direction of line (i.e. flowing towards or away from the node) is irrelevant. Nodes are given a type code, these are listed in the table below:

Code	Meaning	Definition
S	Source	A node which has no polylines flowing into it.
M	Mouth	A node which has no polylines flowing out of it.
P	Pseudo-node	A node which has 1 polyline flowing in and 1 polyline flowing out.
C	Confluence	A node which has 2 or more polylines flowing in and 1 polyline flowing out.
D	Divergence	A node that has 1 polyline flowing in but has 2 or more polylines flow out.
B	Both confluence & divergence	A node that has 2 or more polylines flowing into it and 2 or more polylines flowing out.

All nodes feature class

A screen shot of the All nodes layer, note the additional two fields valency and node type.

The output Feature Class names are: fcMouthsNodes, fcSourceNodes, fcPseudoNodes and fcNodes and are stored in the File GeoDatabase found in ..\RivEX_Workspace\Outputs\fGDB_Nodes.gdb

Warnings

These datasets are extracts from the river network and not a live link to the network. If you have subsequently edited the network then you will have likely modified the network topology and the number of nodes (and possibly position) will have changed. In this case you will want to repeat the extraction of the node layers.

With the release of ArcGIS Pro 3.2.1 a switch control appears on parameters that accept tables\feature classes, do not interact with it! More advice here.

Limitations

All polylines in the river network are processed, if a selection existed this is cleared prior to processing.

Code sample

A minimum code example showing how to call this tool in a python script. This can be run in console or your preferred IDE. If you right click on the tool in the RivEX toolbox and select properties you can view parameter order.

import arcpy

# Import RivEX toolbox
arcpy.ImportToolbox(r"C:\RivEX_ArcPro\RivEX.atbx")

try:
# Input river Feature Class
fc = r"C:\Temp\ORN\ORN.gdb\ORN"

# Run RivEX tool, extracting out only source nodes
res = arcpy.scrNodes_RivEX(fc, "Source nodes")

# Get source node Feature Class
fcSources = res.getOutput(0)

# Get a count on number of nodes extracted
res = arcpy.GetCount_management(fcSources)
n = int(res.getOutput(0))
print("Number of sources extracted = " + str(n))
except arcpy.ExecuteError:
print("FAILED to extract node layer")