Distance Analysis

There are several distance mapping tools for measuring both straight-line (Euclidean) distance and distance measured in terms of other factors such as the cost to travel over the landscape.

Calculating the accumulated cost of traveling can provide you with a rich set of information from which to make decisions. For example, the accumulated least cost of travel within a 200-mile radius to a number of processing mills can be calculated, taking into consideration obstacles to travel. Road and waterway costs can be assigned to restrict travel.

This map shows the results of a spatial model to calculate the least cost path between a stand of forest being cut and the nearest sawmill.
Click on image to enlarge

There are two main ways to perform distance analysis in Spatial Analyst: straight line or Euclidean distance and cost distance. The Euclidean distance functions measure straight-line distance from each cell to the closest source, the source identifies the objects of interest such as wells, roads, or a school. The distance is measured from cell center to cell center. Not only can you determine for each cell which source is closest (allocation), but you can also calculate the distance to that source and in what direction it lies.

The cost distance functions (or cost-weighted distance) modify Euclidean distance by equating distance with a cost factor, which is the cost to travel through any given cell. For example, it may be shorter to climb over the mountain to the destination, but it is faster to walk around it. The cost allocation function identifies the nearest (or least costly) source cell based on accumulated travel cost. The cost direction function provides a road map, identifying the route to take from any cell, along the least cost path, back to the nearest source.

Using the cost distance functions, you can create distance and direction rasters and compute the least cost (or shortest) path from a chosen destination to your source point. The cost distance analysis is guaranteed to be the cheapest route (relative to the cost units defined by the original cost raster). The path distance functions, also known as surface-weighted distance functions, add additional factors beyond the cost surface such as the incorporation of vertical and horizontal surface factors to account for actual travel distance over the terrain being longer than the planimetric distance or the higher cost for traveling uphill than downhill.

Available Distance Analysis tools include:

Cost-Weighted Distance
Cost-Weighted Direction
Cost-Weighted Allocation
Straight-Line Distance
Straight-Line Direction
Straight-Line Allocation
Surface-Weighted Distance
Surface-Weighted Direction
Surface-Weighted Allocation
Least Cost Path
Corridor

Next: Surface Interpolation


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