Page 257 - Laboratory Manual in Physical Geology

A. AERIAL PHOTOGRAPH: a flat picture or image of B. PLANIMETRIC MAP: a flat representation of Earth’s
Earth’s surface. surface showing horizontal positions of feature.

Light duty road
Highway

Unimproved (unpaved) road
N
Topographic contour lines
(lines of equal elevation in feet
above sea level)

Green color indicates forest

0 1 km

C. TOPOGRAPHIC MAP: a flat representation of Earth’s
surface showing horizontal positions of features plus
elevations of the landscape.
FIGURE 9.1 Comparison of an aerial photograph with planimetric and topographic maps. (Courtesy of USGS)

intersection of imaginary reference lines. The most meridian, and points in the Western Hemisphere are
traditional geographic coordinate system consists of located in degrees west of the prime meridian. There-
reference lines of geographic latitude and longitude. fore, any point on Earth (or a map) can be located by its
latitude-longitude coordinates. The latitude coordinate
Latitude-Longitude Coordinate System of the point is its position in degrees north or south of
Earth’s spherical surface is divided into lines of latitude the Equator. The longitude coordinate of the point is
( parallels ) that go around the world parallel to the Equa- its position in degrees east or west of the prime merid-
tor, and lines of longitude ( meridians ) that go around ian. For example, point A in FIGURE 9.2 is located at
the world from pole to pole ( FIGURE 9.2 ). There are coordinates of: 20° north latitude, 120° west longitude.
360 degrees (360°) around the entire Earth, so the dis- For greater detail, each degree of latitude and longitude
tance from the Equator to a pole (one-fourth of the way can also be subdivided into 60 minutes 60′, and each
around Earth) is 90° of latitude. The Equator is assigned minute can be divided into 60 seconds (60″).
a value of zero degrees (0°) latitude, the North Pole is
90 degrees north latitude (90°N), and the South Pole Quadrangle Maps. Most depict rectangular sections
is 90 degrees south latitude (90°S). The prime meridian of Earth’s surface, called quadrangles. A quadrangle is a
is zero degrees of longitude and runs from pole to pole relatively rectangular area of Earth’s surface, bounded by
through Greenwich, England. Locations in Earth’s East- lines of latitude at the top (north) and bottom (south)
ern Hemisphere are located in degrees east of the prime and by lines of longitude on the left (west) and right

Topographic Maps and Orthoimages ■ 229