Some Concepts That Underpin GIS - Introducing Geographic Information Systems with ArcGIS - page 13

(5,3,4)

5

4 units

5

4

4

3

3 (5,3,0)

2

2

1

1

FIGURE 1-6 3-D Cartesian coordinate system

Spherical Coordinate Systems

A spherical coordinate system is another way to reference a point in 3-D space. It also requires three
numbers. Two are angles, and the third is a distance. Consider a ray (a line) emanating from the origin.
The angles determine the direction of the ray. See Figure 1-7.

The latitude-longitude graticule (a gridded reference network of lines encompassing the globe) is based
on a spherical coordinate system. As often happens, different fields of endeavor use different descriptive
approaches. Here, referencing navigation and Earth location issues requires a different system from

FIGURE 1-7 Spherical coordinate system
showing latitude 55° North and longitude
60° East