Geographic Location Systems
In this chapter you will learn about:
¾ Latitude and longitude
¾ Universal Transverse Mercator (UTM)
¾ U.S. Public Land Survey
¾ Other geographic location systems
Geographic location systems or coordinate systems were developed as a tool to describe specific
geographic locations and are used for navigation and mapping. Generally, they consist of a grid of
imaginary intersecting lines which are used to describe a position on a map. Most of these systems use
coordinate values, which are expressed as numeric or alphanumeric characters, to define geographic
locations. Coordinate systems are based on reference points from which position measurements are
made. For example, the reference points for latitude and longitude are the prime meridian and equator.
This chapter discusses two types of global geographic location systems commonly used in the United
States – latitude/longitude and UTM. Then, it describes the U.S. Public Land Survey (section,
township, and range) and other types of geographic location systems.
Refer to Chapter 6, Navigation and Field Mapping, for information on how to plot and map points using
geographic location systems.
Basic Land Navigation
Latitude/longitude is a global system which precisely identifies locations using the equator as a reference
point for latitude and the prime meridian as a reference point for longitude (Figure 3-1).
Latitude lines circle the world parallel with the equator, running in an easterly and westerly direction.
These lines are identified by their position either north or south of the equator. The equator is 0° latitude
and the North Pole (90° N) and South Pole (90° S) are both 90° latitude. All other point