Road Network Data Model Example

To better understand the relationship of the road network data files we will work through a simple illustrative example.


This example is to help understand how the road model data files link together. This example is not intended as a demonstration of how to assemble the road network data (for any realistically sized problem this manual method would be unwieldy). The Build Road Segments tool is intended for this purpose, and will assemble the input files quickly and correctly if provided with clean inputs.

First let's start with a look at the features that we want to represent. These include the six block shapes on the landscape, the mill destination, and several roads drawn in blue (see Figure 184, “The sample forest”).

Figure 184. The sample forest

The vertices file contains the list of nodes at the end of each line segment (see Figure 185, “Nodes at the segment end points”). The node identification labels and X-Y locations are extracted from the spatial road segment data. Two or more road segments meeting at a junction should have coincident end points and will share the same node (same node ID and coordinate points). In this simple example five nodes are defined for the end points of the four road segments.

Figure 185. Nodes at the segment end points


   NODE, X, Y
   1, 3110931, 1209612 
   2, 3161970, 1362755
   3, 3462627, 1557789
   4, 3525963, 1242287
   5, 3806183, 1291875      


The spatial file should be prepared as a connected network where the end points of the lines that meet at a junction have the exact same location with no gaps. When the nodes are correctly matched the build road matrix tool process will automatically assign the node identification labels, or a GIS preprocessing step may be used to assign node labels to each segment.

Four roads segments define the road network (see Figure 186, “Segments in the road network”). The segments file contains details about each segment, including the segment identifier, the id values of the nodes at the end points of the segment, the cost characteristics. The road segments have a directional orientation from the starting node to the ending node. The DIRECTION field indicates the direction of travel allowed over the segment.

Figure 186. Segments in the road network


     Segment.1, 2, 1, 13.82521, 47.652, 0.0, 0.0019, 3
     Segment.2, 4, 2, 27.46425, 34.92, 0.0, 0.00146, 3
     Segment.3, 3, 2, 33.41659, 86.838, 0.0, 0.0036, 3
     Segment.4, 5, 3, 37.11992, 74.239, 0.0, 0.0031, 3

The final two core files that define the road network structure describe the connection between blocks or destinations and the closest nodes (see Figure 187, “Linkages to the road network”). In our example, the six blocks have been assigned network "on ramps" at the closest node. Several blocks share the same node linkage. The analogy to the real world is that the nodes are 'landings' where the trucks would be loaded, and wood is forwarded from the stands to these landings. When developing the road network care should be taken to provide regularly spaced nodes so that forwarding distances remain reasonable.


Each block may only connect with a single node. If the blocks are so large that forwarding to a single landing seems unreasonable then consider dividing the input blocks in to smaller parts.

The destinations file describes the nodes where the destinations are located. The Patchworks model will automatically calculate the flow of wood from stump to mill according to the accounts and objectives that you have set.

Figure 187. Linkages to the road network


   Block.1, 2
   Block.2, 3
   Block.3, 5
   Block.4, 4
   Block.5, 4
   Block.6, 5

   1, destination.MILL


Define a sufficient number of segments and nodes over the planning area to ensure the all blocks will have a realistic forwarding distance from an entry point. Long segments may need to be divided in to a series of shorter segments to provide additional linkage points.