Objective: Determine the least cost path of a feeder line running from transmission station to manufacturing plant over a predefined cost surface, and compare this to the shortest path route
The concept of a ‘cost distance’ is typically used to model movement through space where frictional elements that might impede movement are defined. Here, the cost of having a feeder line run between the source and destination feature is studied according to the different frictional values assigned to areas based on their land use. See attached map, “Transmission to Manufacturing Plant Route: Shortest versus Least Cost Path.”
Transmission to Manufacturing Plant Route: Shortest versus Least Cost Path
The length of the shortest path route was calculated by summing the attribute ‘value’ and ‘count’ products from the extracted land data layer. It was found to be approximately 38, 925 meters long with a total frictional cost of 1, 871, 875 units. The length of the least cost path is found directly on the attribute table of the associated data layer and is approximately 50, 354 meters with a total frictional cost of 281, 255.10 units.
Distinguishing between the least cost path and the shortest path route
Least Cost Path: The land area surrounding the start (source feature) and end point (destination feature) of the manufacturer’s feeder line are assigned friction values that indicate the ‘cost’ of passing by areas based on their land use. So the least cost route should pass by open areas and resource and industrial areas that are base cost, and try to avoid passing high cost areas like residential neighborhoods and water bodies. After creating a matrix that ranks the spatial variability of cost via land use, the least cost path route is drawn along a path that avoids high cost areas. This makes the route dependent on the assigned friction values of passing high versus low cost areas: wherein cost defines the monetary/economic, social, political, and environmental drawbacks of constructing the feeder line along certain areas.
Shortest (Euclidean Distance) Path: The shortest path route is generally a straight line path that runs from some starting point (the transmission station) to some end point (the manufacturing plant) and does not consider the social implications of friction cist. For example, it does not take into account the hindrance that a feeder line would cause in population dense areas nor the environmental complications in vegetation and fauna population dense areas.
Representation of Water Features in the Least Cost Path Route: Data for water features need to be converted from vector to raster data on the map after edge matching lakes to form closed polygons for the analysis. The raster map reduces the representation by opting out streams and thereby allowing the least cost path of the prospective feeder line to cross these streams. This problem mainly concerns how grids representing rivers allow crossing and so we can convert the domain shape of resolution from a square grid to a hexagonal grid when converting from the vector to raster representation of the data. The six sides of each hexagon on the grid will disallow crossing by closing gaps between each repeated polygon.
Routing over Existing Transmission Lines and Highways: For the least cost path to avoid routing over highways, assign medium to high frictional values to major roads and highways by adding another column in the attribute table of the associated data layer: named ‘cost.’ Input some frictional value greater than residential and commercial areas or some friction value less than or equal to those of water bodies.