Spatial Analysis Based on Raster Data Processing - Introducing Geographic Information Systems with ArcGIS - page 517

FIGURE 8-49
22. Using the Identify tool, with the “Identify from” field being TCostOnecell, examine the total cost of
traversing the cells due north of the source cell (pick the third cell directly above the source cell).
What is that cost? ____. Now look at the total cost of traversing the same distance but crossing
from the east of the source cell (pick the third cell directly to the east of the source cell). What
is it? _____. It is obviously cheaper to come from the east (cost is $10.50) than from the north
($15). The overall range of costs is from 0 (from the source cell to the source cell) to approximately
$82. Again use the Identify tool to display the values of the Toll cells that are traversed. To come
from the east, one need only traverse cells with costs of 0.35 per kilometer or less. To come from
the north, the cell costs are 1.15, 1.05, 0.95, and so on. The most expensive trip is from the
northeasternmost cell—it is furthest away and in an area where the cost per cell is highest.
23. Check out the contouring capability of the Spatial Analyst: In the Spatial Analyst toolbar use
the drop-down menu to select TCostOneCell. Click the Create Contour button. Then click
various places on the raster. The lines that appear are estimates of constant cost. That is, from
any point on a given contour line, it should cost about as much to go to Onecell as from any
other point on that line. Of course, this won't be exact, since the cost jumps incrementally each
time you cross a cell boundary, but you see the idea. Use MapTips on TCostOneCell to check
out the cells that are crossed by a contour line. Pick another line and check those cells.
24. Erase the contour lines by pressing the Select Elements button, dragging boxes around the
contour lines, and pressing the Delete key or Delete button on the Standard toolbar.