Geometry of the Sphere - Spatial Mathematics: Theory and Practice through Mapping - page 8

meridians. The reason for this is that since the meridians converge
at the ends of the polar axis, it follows then that each meridian
represents the passage of one hour of time—given the agreement
to partition a day into 24 hours—24 times 15 is 360, so that merid-
ians also mark time, at least in a general way and independent of
political and social convention regarding awkward partitioning of
urban areas, and so forth.
• Bounds of measurement (see Figure 1.6).
• Latitude runs from 0° at the Equator to 90°N or 90°S at the poles.

North pole

90° N

60° N

60° N
30° N

30° N

90°

30°

Equator Equator

0° 0°

90°

30° S 30° S

60° S

60° S

90° S

180°

South pole

150° W 150° E

120° W 120° E

180°

90° E

90° W

90°

60° W 60° E

30° E

30° W

0°

0° Prime
Meridian

180°
International
Date Line

Figure 1.6 Bounds of measurement for latitude and longitude. Source: Based on Geo-
Systems Global Corporation (later MapQuest) image, 1998.