Analysis of GIS Data by Simple Examination - Introducing Geographic Information Systems with ArcGIS - page 399

that are Nearest to the Input Features), pick Wells. For the search radius, type the number you
found previously for the diagonal distance across the island. Check to see that the units are
meters. Click the boxes that will specify the location of the well (called Function Name) and the
angle from the house to the well. Run the tool by clicking OK. Close it when the Close button
appears. Dismiss ArcToolbox to get more room on the screen. Make sure ArcCatalog is closed.
9. Again examine the attribute table of Houses. What are the field names?
____________, ____________, ____________, ____________, ____________, ____________.
10. Run statistics on NEAR_DIST. What is the total number of meters of pipe that would be required
to connect each house to its nearest well? ____________.
11. Label each well with its OBJECTID. Label each house with its near feature ID (NEAR_FID)
attribute value. “Eyeball” the results to verify that correct houses were assigned to wells. Label
each house with its NEAR_DIST. Use the measure tool on a couple of house-well pairs to verify
that the Near command got it right in the attribute table.
12. Label the houses with NEAR_ANGLE. Check to see that things look right. Realize that the angle
given from the house to the well is the “math” version (0 degrees is the positive x-axis, the
angle increases counterclockwise), rather than the compass version (0 degrees is the positive
y-axis, the angle increases clockwise). Check the Help file for details. This is just one of the
wrinkles one encounters in ArcGIS—the kind of thing that gets you paid the big bucks when you
graduate—unless you go into teaching, that is.
13. Extra credit problem: Could you reduce the cost of putting in water lines by using mains (say
using larger pipes to some intermediate junction) and then smaller pipes from there? You could
augment the wells feature class by putting in pseudo-wells (junctions) and experiment with
those. What is the shortest length of pipe you can find that would do the job? ________. Of
course, this makes the problem more complicated, since you have to figure in the greater cost
of the larger pipe, the additional connections, and so on.
14. Run the Near tool again, this time determining connections between the houses and the
power line. (Re-running the tool will overwrite the previously stored attribute values NEAR_DIST,
NEAR_X, and NEAR_Y, and so on; there is no warning to this effect.) What length of electric
cable would be required? ________. Why are so many of the angles 90 degrees? _____________
___________________________________
Exercise 6-6 (Review)
Checking, Updating, and Organizing Your Fast Facts File
The Fast Facts File that you are developing should contain references to items in the following checklist.
The checklist represents the abilities to use the software you should have upon completing Chapter 6.
___ Double-clicking a toolbar's left end
___ Double-clicking a toolbar's title