Page 65 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

(a) Cylindrical projection
50°N
40°N
S
t
a
n
d
a
30°N 20°N
r
d
p
a
r
a
l
l
e
l
s
160°W
40°W
45.5° 29.5°
140°W
120°W
(c) Conic projection
100°W
Albers equal-area conic projection (two standard parallels)
Map Projections
▲Figure 1.23 Classes of map projections.
170°W
80°W
R
60°W
m
60°N
10°E
170°E
C
t
a
e
r
G
r
i
c
l
e
Great Circle
e
150°W
n
i
l
b
San Francisco
London
30°W 10°W 10°E
Standard line
Mercator projection
Standard line (point)
Gnomonic projection (b) Planar projection
Standard line
Standard line
(d) Oval projection
u
h
Rhumb Line
130°W
110°W
(a) The gnomonic projection is used to determine the shortest distance (great circle route) between San Francisco and London because on this projection the arc of a great circle is a straight line.
(b) The great circle route is then plotted on a Mercator projection, which has true compass direction. Note that straight lines or bearings on a Mercator projection (rhumb lines) are not the shortest route.
▲Figure 1.24 Determining great circle routes.
London
70°N
60°N
50°N
40°N
San Francisco
30°N
130°W 110°W
Chapter 1 essentials of Geography 29
10°W
70°N 60°N
50°N 40°N
30°W
50°W
70°W
90°W
90°W 70°W 50°W