The Optimal Region Connections tool calculates the optimal connectivity network between two or more input regions.
The output is a hosted feature layer.
Learn how Optimal Region Connections works
Examples
The Optimal Region Connections tool can be used in the following scenarios:
- From a suitability model, you have identified 10 of the best habitat patches for bobcats. You want the bobcats to be able to move between the patches through the most effective network of wildlife corridors to maintain genetic diversity within the metapopulation.
- In a disaster relief effort, you have identified five areas where rescue and medical staff camps will be positioned. You want to develop the best network of supply routes between the camps.
- In a timber harvest, you want to create the most cost-efficient network of logging roads to extract the lumber.
- In a firefighting operation, you want to identify the best network of trails to move firefighting resources between various headquarters.
Usage notes
Optimal Region Connections includes configurations for input layers, path settings, and output results.
Input layers
The Input layers group includes the following parameters:
Input region raster or features specifies the raster or feature layer that identifies the regions that will be connected by the optimal network. You can choose a layer using the Layer button, or use the Draw input features button to create a sketch layer to use as the input. For feature inputs, a count of features is displayed below the layer name. The count includes all features in the layer, except features that have been removed using a filter. Environment settings, such as Processing extent, are not reflected in the feature count.
If the region input is a raster, the regions are defined by groups of contiguous (adjacent) cells of the same value. Each region must be uniquely numbered. The cells that are not part of a region must be NoData. The raster type must be integer, and the values can be either positive or negative.
If the region input is a feature dataset, it can be polygons, polylines, or points. Polygon feature regions should not be composed of multipart polygons.
When the input regions are features, the region locations are converted to a raster internally, with the resulting regions having unique values, before performing the analysis. When multipoint data is provided, the tool randomly selects one of the points at the location as the region value.
The resolution of the raster can be controlled with the Cell size environment. By default, the resolution will be set to the resolution of the Input cost raster value if one is provided. The resolution will be set to the resolution of the Input barrier raster or feaures value if only a barrier raster is provided. If no other rasters are specified, the resolution will be determined by the shorter of the width or height of the extent of the input feature in the input spatial reference, divided by 250.
When using polygon feature data for the input region data, take care with how the cell size is handled when it is coarse, relative to the detail present in the input. The internal rasterization process uses a cell center method for the cell assignment type. This means that data that is not located at the center of the cell will not be included in the intermediate rasterized region output, so it will not be represented in the calculations. For example, if the regions are a series of small polygons (such as building footprints) that are small relative to the output cell size, only a few may fall under the centers of the output raster cells, seemingly causing most of the others to be lost in the analysis.
To avoid these situations, as an intermediate step, you can rasterize the input features to the appropriate resolution directly using the Convert Feature to Raster tool. Then use the resulting output as input to the Optimal Region Connections tool.
If the input regions are rasters and if any of the regions are disconnected, the resulting paths will be to the part of the region that is closest or cheapest to reach.
If a region falls on NoData in the mask or any of the corresponding input rasters, it is ignored in the analysis, and no paths will be created to that region.
The default processing extent is the same as that of the Input cost raster value if one is provided; otherwise, it will be set to the extent of the input regions.
- The Optional layers group includes the following parameters:
Input barrier raster or features is the layer that defines the barriers. Barriers are obstacles that must be routed around. They can be defined either as raster or feature data. You can choose a layer using the Layer button, or use the Draw input features button to create a sketch layer to use as the input. For feature inputs, a count of features is displayed below the layer name. The count includes all features in the layer, except features that have been removed using a filter. Environment settings, such as Processing extent, are not reflected in the feature count.
For a raster layer, the input type can be integer or float. Any cells that have a value (including zero) will be treated as a barrier. Any cells that are NoData will not be treated as a barrier.
For a feature, the input can be point, line, or polygon. Feature inputs will be converted to a raster internally before being processed.
Where barriers are connected only by diagonal cells, the barriers will be thickened to make them impermeable.
Barriers are also defined by locations where NoData cells exist in the Input cost raster parameter value. In addition, locations that are not within the Mask environment act as barriers. Where NoData is connected only by diagonal cells, they will be thickened with additional NoData cells to make an impermeable barrier.
Input cost raster is the raster layer that will define the impedance, or cost, to move planimetrically through each cell.
The value at each cell location in the cost surface represents the cost-per-unit distance for moving through the cell. Each cell location value is multiplied by the cell resolution while also compensating for diagonal movement to obtain the total cost of passing through the cell.
The values of the cost raster can be integer or floating point. Cost raster values that are negative or zero are invalid but will be treated as small positive cost values. The accumulative cost algorithm is a multiplicative process, and it cannot calculate accumulative cost correctly if cost values are negative or zero. If the cost raster contains those values, and those locations represent areas that are to be excluded from the analysis, turn those cells into NoData before running the tool. You can do this using the Set Null tool. The NoData value is treated as a barrier in this analysis, so any locations that are NoData in the input will be NoData in the result.
To learn more about cost surfaces, see Adjust the encountered distance using a cost surface in the ArcGIS Pro Spatial Analyst extension help.
Path settings
The Path settings group includes the following parameters:
Distance method specifies whether the distance will be calculated using a planar (flat earth) method or a geodesic (ellipsoid) method.
- Planar—The distance calculation will be performed on a projected flat plane using a 2D Cartesian coordinate system. This is the default method.
- Geodesic—The distance calculation will be performed on the ellipsoid. Regardless of the input or output projection, the results will not change.
Connections within regions specifies whether the paths will continue and connect within the input regions.
- Generate connections—Paths will continue within the input regions to connect all paths that enter a region. This is the default method.
- No connections—Paths will stop at the edges of the input regions and will not continue or connect within them.
Results layers
The Result layers group includes the following parameters:
Output optimal connections line name is the name of the output layer that contains the resulting optimal network of paths connecting the input regions.
The name must be unique. If a layer with the same name already exists in your organization, the tool will fail and you will be prompted to use a different name.
The Optional layers group includes the following parameter:
Output neighboring connections line name is the name of the optional output layer that contains the resulting paths from each region to each of its closest or cost neighbors.
The name must be unique. If a layer with the same name already exists in your organization, the tool will fail and you will be prompted to use a different name.
- Save in folder specifies the name of a folder in My content where the result will be saved.
Environments
Analysis environment settings are additional parameters that affect a tool's results. You can access the tool's analysis environment settings from the Environment settings parameter group.
This tool honors the following analysis environments:
- Cell size
- Processing extent
Note:
The default processing extent is Full extent. This default is different from Map Viewer Classic in which Use current map extent is enabled by default.
- Mask
- Output coordinate system
- Snap raster
- Parallel processing factor
Outputs
This tool includes the following outputs:
The Output optimal connections line name layer identifies the optimal network of paths that connect each of the input regions.
The resulting network connects the regions in the least-cost or shortest distance possible. Using the network, a traveler can reach any region from any other region (possibly passing through another region) using the network.
Each path (or line) is uniquely numbered, and the following additional fields in the attribute table store specific information about the path:
- Pathid—The unique identifier for the path
- Pathcost—The total accumulative distance or cost for the path
- Region1—The first region the path connects
- Region2—The other region the path connects
This information provides insight into the paths in the network.
Since each path is represented by a unique line, there will be multiple lines in locations where paths travel the same route.
The optimal output network is created from the paths produced in the optional neighboring connections output. The paths in the optional neighboring connections output are converted to graph theory. The regions are the vertices, the paths are the edges, and the accumulative distances or costs are the weights for the edges. The minimum spanning tree is calculated from the graph representation of the paths to determine the optimal path network necessary to travel between the regions.
If no cost surface is specified, the neighbors are identified by Euclidean distance. When this is the case, a region's closest neighbor is the one that is closest in distance. When a cost surface is provided, the neighbors are identified by cost distance, making a region's closest neighbor the cheapest one to travel to. A cost distance allocation operation is performed to identify the regions that are neighbors to one another.
When Generate connections is specified for the Connections within regions parameter, each optimal path first reaches the outer boundary of the polygon or multicell region. From the perimeter of the region, the tool continues the paths through the region with additional line segments, allowing for points of entry and exit between regions and movement within them. There is no additional distance or cost of movement along these line segments.
Depending on the configuration of the input regions and their allocation neighbors, a path can pass through an intermediate region to reach a neighboring region. That path will incur costs as it moves through that intermediate region.
The Output neighboring connections line name layer identifies the paths from each region to each of its closest or cost neighbors.
Each path (or line) is uniquely numbered and the following additional fields in the attribute table store specific information about the path:
- Pathid—The unique identifier for the path
- Pathcost—The total accumulative distance or cost for the path
- Region1—The first region the path connects
- Region2—The other region the path connects
This information provides insight into the paths in the network and is useful when deciding which paths should be removed if necessary.
Since each path is represented by a unique line, there will be multiple lines in locations where paths travel the same route.
The optional neighboring connections output can be used as an alternative network to the minimum spanning tree network. This output connects each region to its neighboring closest or cost regions, producing a more complex network with many paths. The feature layer can be used as is or as the base from which to create a new network.
Usage requirements
This tool requires the following user type and configurations:
References
- Douglas, D. "Least-cost Path in GIS Using an Accumulated Cost Surface and Slopelines", Cartographica: The International Journal for Geographic Information and Geovisualization, 1994, Vol. 31, No. 3, DOI: 10.3138/D327-0323-2JUT-016M
- Goodchild, M.F. "An evaluation of lattice solutions to the problem of corridor location", Environment and Planning A: Economy and Space, 1977, Vol. 9, pages 727-738
- Sethian, J.A.. "Level Set Methods and Fast Marching Methods", Evolving Interfaces in Computational Geometry, Fluid Mechanics, Computer Vision, and Materials Science, Cambridge University Press, 2nd Edition, 1999
- Warntz, W. "Transportation, Social Physics, and the Law Of Refraction", The Professional Geographer, 1957, Vol. 9, No. 4, pages 2-7
- Zhao, H. "A fast sweeping method for Eikonal equations", Mathematics off Computation, 2004, Vol. 74, No, 250, pages 603-627
Resources
Use the following resources to learn more:
- How Optimal Region Connections works in ArcGIS Pro
- Optimal Region Connections in ArcGIS REST API
- optimal_region_connections in ArcGIS API for Python
- Optimal Region Connections in ArcGIS Pro with the Raster Analysis extension
- Optimal Region Connections in ArcGIS Pro with the Spatial Analyst extension