This raster analysis portal tool is available when you are signed in to an ArcGIS Enterprise portal that has ArcGIS Image Server configured for Raster Analysis. When the tool is run, ArcGIS Pro serves as a client and the processing occurs in the servers federated with ArcGIS Enterprise. The portal tool accepts layers from your portal as input and creates output in your portal.
The input raster layer supports a layer from the portal, a URI or URL to an image service, or the output from the Make Image Server Layer tool. The input feature layer can be a layer from the portal or a URI or URL to a feature service. This tool does not support local raster data or layers. While you can use local feature data and layers as input to this portal tool, best practice is to use layers from your portal as input.
When the input destination data is a raster, the set of destination cells consists of all cells in the Input Raster or Feature Destinations that have valid values. Cells that have NoData values are not included in the source set. The value zero is considered a legitimate destination. A destination raster can be created using the extraction tools.
When using feature data for the input destinations, care must be taken with how the output cell size is managed, particularly when it is coarse relative to the detail present in the input. An internal rasterization process using the Feature to Raster tool is applied. This means that data that is not located at the center of the cell will not be included in the intermediate rasterized destination output, and will not be represented in the distance calculations. For example, if your destinations are a series of small polygons, such as building footprints, that are small relative to the output cell size, it is possible that only a few of them will fall under the centers of the output raster cells, seemingly causing many of the others to be lost in the analysis.
To avoid this situation, as an intermediate step, you could rasterize the input features directly with the Feature to Raster tool and set the Field parameter. Then use the resulting output as input to the particular distance tool you want to use. Alternatively, you could select a small cell size to capture the appropriate amount of detail from the input features.
Before generating an optimal path, usually one of the following tools is used to create a distance accumulation raster and a back direction raster: Distance Accumulation or Distance Allocation. These are required inputs to generate an optimal path.
The optimal path created can be a flow path based on D8 flow direction. To generate an optimal path in this way, use a D8 flow direction raster as input for the Input Back Direction or Flow Direction Raster. You also need to supply an Input Distance Accumulation Raster; the Input Distance Accumulation Raster is not used to determine the path. Whether you use a constant raster or a digital elevation model (DEM), your path will be the same; only an attribute value on your path will vary. See the Flow Direction tool for more information on D8 flow direction rasters.
To create paths that cross the edge of the projection, the rasters used as inputs for the Distance Accumulation Raster and Back Direction Raster parameters must have been created at the full global extent, in either a cylindrical projection or a geographic output coordinate system, while using the Geodesic option for the Distance Method parameter.
The values on the output optimal path represent the number of paths at a given location. In many cases, paths follow the same route, leaving a source and then diverging to different destinations. For example, a value of one indicates that there is only one optimal path at a given location, while a value of five means at that location there are five optimal paths going through that cell in the study area.
To generate an optimal path, the Cell size environment setting is ignored and the cell size of the Input Back Direction Raster is used to calculate the output raster. The pattern of the back direction raster would be seriously altered if it were resampled to a different resolution. To avoid any confusion, the cell size should not be set when using this tool.
Unlike most other Raster Analysis tools, Optimal Path As Line will ignore the following environment settings: Output Coordinate System, Extent, Cell Size, and Snap Raster. The pattern of the back link raster would be significantly altered if it were resampled or reprojected, resulting in an incorrect path.
