Laboratory Manual for Introductory Geology 4e

same angular distance east or west of the prime meridian. The maximum value for
longitude is 180° E or 180° W (the international date line). Remember: When stating a
location, you must always indicate whether a point is north or south of the equator and whether
it is east or west of the prime meridian.
Latitude and longitude readings are typically reported in degrees (°), minutes (′),
and seconds (″) (for example, 40°37′44″ N, 73°45′09″ W). There are 60 minutes in a
degree and 60 seconds in a minute. For reference, 1 degree of latitude is equivalent
to approximately 69 miles (111 km), 1 minute of latitude is about 1.1 mile (1.85 km),
and 1 second of latitude is about 100 feet (31 m). The same kind of comparison can be
made for longitude only at the equator because the meridians converge at the poles, so the
distance between degrees of longitude decreases gradually toward the poles (Fig. 8.3b).
EXERCISE 8.2
The Latitude/Longitude Grid
Name:
Course:
Section:
Date:
(a) Describe the locations of the points indicated by the stars in the figure below, on which parallels of latitude and
meridians of longitude are spaced 15° apart. Remember to specify N or S for latitude, W or E for longitude.
i
ii
iii
i
(b) With the aid of a globe or map, determine the geographic features that are located at
●●
45°00′00″ N, 90°00′00″ W
●●
15°00′00″ N, 30°00′00″ E
●●
30°00′00″ S, 90°00′00″ W
(c) With the aid of a globe or map, determine the latitude and longitude of your geology laboratory as accurately
as you can. How might you locate the laboratory more accurately?
(d) If you have access to a GPS receiver, locate the corners of your laboratory building. Draw a map (on a
separate piece of paper) showing the building’s location, orientation, and distances between the corners.
(continued)
8.3 MAP ELEMENTS
203