Characteristics and Examples of Spatial Data - Introducing Geographic Information Systems with ArcGIS - page 151

How many DEM posts are there? (see Count) _________________.
What is the height of the shortest one? _____________.
What is the height of the tallest one? ______________.
What is the height of the average post to the nearest tenth of a foot? ______________.
42. For Method specify Natural Breaks (Jenks); also specify 30 classes. Examine the histogram.
Specify 40 columns for it. Your Classification window should look like Figure 2-32. Note that
the great majority of the elevations lie around the 1000-foot level. However, there are some at
around the 550-foot level, which you may recall from the DRG, is near the normal pool elevation
of the river. Click OK. Click Apply. Dismiss the Layer Properties window by clicking OK. Note the
range of elevation values, and the associated color symbols, by widening and scrolling the T/C.
Then zoom to the GPS track again.
FIGURE 2-32
43. Zoom in on the part of the GPS track that is within the Coletown DEM, including the island.
Click again on the Identify tool and unhide the Identify window if necessary. Notice how quickly
the elevation changes in the vicinity of the river. Getting the results from the COLE_DEM, what
is the elevation of the surface of the river? ________. Record an elevation taken on the island.
___________. Does the DEM river elevation agree with what you wrote before for the normal
pool elevation? How much different? ________. Let the Identify window auto hide again.
44. A faster way to see the values of the DEM posts is to right-click the DEM layer name, then
click Properties and switch to the Display tab. Check the Show MapTips check box and then
click Apply and OK. Now when you move the mouse cursor around the map, even if the Identify