Geology Reference
In-Depth Information
FIGURE 2.12 Stereopair aerial photos of Meteor Crater, Arizona. The scale of these photographs is about 3,500 ft/in. The crater is
approximately 600 ft deep. (Reprinted by permission from Avery, 1968. Photograph courtesy of U.S. Department of Agriculture.
Copyright © 1968 T. Eugene Avery)
Remember that scale is described as a ratio (such as
1:24,000), and that the units of measure must be the
same on the photo and the ground (for example,
inches on both photo and ground, not inches on the
photo and feet or miles on the ground).
3. On Figure 2.12, label any other visible relief features, vege-
tation, roads and buildings.
Boston
The following questions refer to Figure 2.13, which is in the
color map section at the back of this topic. This is a high alti-
tude photograph of the Boston, Massachusetts, area. The
Charles River enters from the middle west of the photo-
graph. The Mystic River enters the northern Inner Harbor
from the west, and Chelsea Creek enters the Inner Harbor
from the east. The channel with the ship docked south of
Logan Airport is oriented E-W. The instructor will identify
place names and locations of specific sites or you can consult
topographic or road maps.
Stereoscopic Viewing
Air photos are usually taken in sequence along a path of
flight so that there is considerable overlap, such that any
given feature will appear on at least two different photos.
Viewing these overlapping photos (a stereopair) through
a stereoscope results in a three-dimensional view of the
surface. Figure 2.12 is a stereopair that allows the third
dimension to be easily seen with a standard stereoscope.
Note that features on the ground will appear to be verti-
cally exaggerated on stereo photographs.
4. Study the color high altitude photograph (Figure 2.13)
using a magnifying glass or hand lens if necessary to identify
geologic and cultural features. Label the following features
on the photo, using the corresponding numbers 1-15.
1. park
2. airport runway
3. airport terminal with planes
4. tidal flat
5. beach
6. star-shaped fort (SE quarter of image)
7. road
8. bridge
9. railway
10. pond
11. small boat
12. large docked ship
13. racetrack
QUESTIONS 2, PART C
Meteor Crater
1. Examine Figure 2.12. Given the scale in the caption, what
is the approximate diameter of the crater?
2. Using a stereoscope to see the third dimension in Figure
2.12, outline the floor of the crater and mark the lowest point
with an "L."
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