Spatial Analysis Based on Raster Data Processing - Introducing Geographic Information Systems with ArcGIS - page 515

FIGURE 8-48
The raster of source cells that serves as input to this tool may consist of several single cells, clumps
of cells (contiguous cells), a linear structure of several cells, or any combination of these. For each cell
in the output raster, the straight-line distance to the closest source cell is calculated. This happens
automatically. You simply apply the straight-line distance tool, as you did in the previous steps, and the
newly generated raster contains the closest distances.
14. Arrange the entries in the T/C so that from top to bottom they are ordered Square_Grid,
Manycells, then DistManycells. In the Properties > Symbology window of DistManycells Display
NoData as white. See Figure 8-48.
15. Examine the distance raster, making sure that DistManycells is the active dataset in the
Identify tool. Verify that some distances shown by cells in the new dataset are indeed
associated with the closest source cells in Manycells. The cutoff value of 30 kilometers for
the distance resulted in some NODATA cells in the new dataset. Use the Measure tool to
verify that the NODATA cells, shown in white, are more than 30 units away from any source
cells. Note that 30 is the largest value in the legend of DistManycells. Use the Spatial Analyst
toolbar to make a histogram of DistManyCells. How many cells are about 20 kilometers
away from a source cell. Count them on the map as well. Using CellToool to help. Close the
Histogram window.