In lesson 1 of the cost-distance analysis lessons, a cost surface was created. Cost surfaces are an integral component for any cost-distance analysis workflow. This lesson will cover the first cost-distance analysis workflow, connecting multiple input regions with the optimum (least-cost) network of paths. As a result, the mover can move through the network traveling from any patch to any other patch in the least-cost manner possible.
This lesson is divided into two sections:
- Opening and editing the ModelBuilder model
- Creating a network with the Cost Connectivity tool
This lesson continues on the data that you downloaded in lesson 1. If you have not downloaded the data, see the first section in Lesson 1: Creating a cost surface.
Opening and editing the ModelBuilder model
- Open the CostConnectivity map document located in the CostDistanceAnalysis folder that you downloaded in lesson 1 by double-clicking the file.
- Explore the CostSurface and Regions layers by using the Identify tool (found on the Tools toolbar).
- To help keep the workflow organized, you will track the tools you use in a ModelBuilder model. Within the CostDistanceAnalysis folder is a folder named Toolboxes, with a toolbox named CostDistanceAnalysisToolbox.tbx, which contains several models. One of these models will be used to create an optimum network of paths. Open ArcCatalog by clicking the ArcCatalog icon in the taskbar, which will open the Catalog window. From the Catalog window, open the CostConnectivity model by right-clicking the model and clicking Edit.
Creating a network with the Cost Connectivity tool
The Cost Connectivity tool requires two input layers: a dataset of regions and a cost surface. Regions usually represent isolated locations that need to be connected. The regions you will use in this lesson are the results of a bobcat suitability model created in the Understanding the suitability modeling workflow case study. The second input, the cost surface, indicates how costly, or taxing, it is to travel across each map unit. The cost surface used for this lesson was created in Lesson 1: Creating a cost surface.
- From the table of contents, drag the Regions layer into the CostConnectivity model.
- Add the CostSurface layer from the table of contents to the CostConnectivity model.
- Calculating the optimum network, or minimum spanning tree, that connects the regions is done with the Cost Connectivity tool. This tool requires the ArcGIS Spatial Analyst extension extension, so first make sure the extension is turned on by clicking the Customize tab in the ArcMap taskbar. Choose the Extensions option from the dropdown list, and check the ArcGIS Spatial Analyst extension checkbox to turn it on.
- Once the extension is turned on, access is granted to the ArcGIS Spatial Analyst extension tools. Click the ArcToolbox button in the Standard toolbar. Browse to the Cost Connectivity tool in the Distance toolset in the Spatial Analyst Tools toolbox.
- Drag the Cost Connectivity tool into the CostConnectivity model and place it to the right of the Regions and CostSurface layers.
- Using the Connect tool in the CostConnectivity ModelBuilder model taskbar, connect the Regions layer to the Cost Connectivity tool. Make the connection by clicking the Regions layer first, and then click the Cost Connectivity tool. Choose the Input raster or features region data option.
- With the Connect tool still turned on, connect the CostSurface layer to the Cost Connectivity tool. Choose the Input cost raster option.
- Double click the Cost Connectivity tool to open the tool's dialog box. Type OptimumNetwork in the Output feature class parameter to name the optimum network of paths. The model automatically saves the file into the Output.gdb geodatabase file. To summarize the input and output layers for the Cost Connectivity tool, specify the parameters as follows:
- Input raster or features regions data: Regions
- Input cost raster: CostSurface
- Output feature class: OptimumNetwork
- Click OK to close the Cost Connectivity tool's dialog box.
- Right-click the Cost Connectivity tool and click Run to execute the tool.
- Add the OptimumNetwork output layer to the map document by right-clicking the green OptimumNetwork layer and clicking Add To Display.
- Save the CostConnectivity model by clicking the Save button in the ModelBuilder taskbar. Close the model once it is saved.
- Explore the OptimumNetwork layer by clicking the individual paths making up the network with the Identify tool (found in the Tools toolbar).
- Save the map document by clicking the Save button in the Standard toolbar.
Congratulations! At this point, you have created an optimum network of least-cost paths connecting a series of input regions. In the next lesson you will learn how to create a least-cost path between two specified regions, see Lesson 3: Creating a least cost path.