Creating Block Topology

If you are planning on using patch size or shape targets in your analysis (which is probably a major reason you have chosen PATCHworks!) you will need to create another topology file to define the topological relationships of all the blocks in the planning area. The model needs to know the neighbours of each block. Patchworks requires an explicit criteria to help determine the set of blocks that should be considered neighbours of each other.

The Proximal Topology tool will calculate interblock distances and shared edge lengths for all blocks that are within your specified threshold distance. Being able to define a specific search distance means blocks do not necessarily have to be adjacent to be considered 'neighbours'. This file generated by the Proximal Topology tool is essential in order to use the patching capabilities of the Patchworks model.

[Note]Note
  1. Select "Proximal Topology Tool (raster)" from the Data Prep folder in the Application Launcher and click 'Go'. Click on "Next" in the first dialog box.

  2. Select the blocks file that you have just created as your polygon dataset.

    Polygon data set:QuickTourIII/blocks/blocks.shp

  3. Provide a cell size and threshold search distance for the tool. Our search distance will be much larger for the blocks (200m) as compared to the fragments (20m) since we may wish to calculate disturbance patches with a larger separation distance in the model.

    Cell size: 10

    Distance threshold: 200

    Polygon label: BLOCK

    Output file: QuickTourIII/tracks/blocks_topology_200.csv

Figure 160. Proximal topology for the block shape file


Figure 161. Set Parameters


[Tip]Tip

The threshold search distance should be quite large for the blocks (as compared to fragments) but this distance can be filtered when the model is loaded to something smaller. This allows you to test several distances within the model when doing an analysis of patch sizes.

A single topology file will be loaded into the model upon startup (with or without the distance filtered). There is an excellent section in the section called “Patch Accounts” that will give you more information on how to use topology file in your model.

The required spatial components of our model are complete. At this point we will move into the converting and joining of aspatial stand dynamics for all the stands of the Crowsnest Pass.