Latitude

Maps are flat models of three-dimensional objects. For thousands of years people have used maps to define borders and to find places. The map at the beginning of this chapter was made in 1570. What do you notice about the size and shape of the continents? Today, more information is available to create more accurate maps. The science of mapmaking is called cartography.

Cartographers use an imaginary grid of parallel lines to locate exact points on Earth. In this grid, the equator horizontally circles Earth halfway between the north and south poles. The equator separates Earth into two equal halves called the northern hemisphere and the southern hemisphere. Lines on a map running parallel to the equator are called lines of latitude. Latitude is the distance in degrees north or south of the equator.The equator, which serves as the reference point for latitude, is numbered 0° latitude. The poles are each numbered 90° latitude. Latitude is thus measured from 0° at the equator to 90° at the poles.

Locations north of the equator are referred to by degrees north latitude (N). Locations south of the equator are referred to by degrees south latitude (S). For example, Syracuse, New York, is located at 43° N, and Christchurch, New Zealand, is located at 43° S.

Degrees of latitude Each degree of latitude is equivalent to about 111 km on Earth’s surface. How did cartographers determine this distance? Earth is a sphere and can be divided into 360°. The circumference of Earth is about 40,000 km. To find the distance of each degree of latitude, cartographers divided 40,000 km by 360°. To locate positions on Earth more precisely, cartographers break down degrees of latitude into 60 smaller units, called minutes. The symbol for a minute is ΄. The actual distance on Earth’s surface of each minute of latitude is 1.85 km, which is obtained by dividing 111 km by 60΄.

A minute of latitude can be further divided into seconds, which are represented by the symbol ˝. Longitude is also divided into degrees, minutes, and seconds.