Lesson Objectives

• Understand the difference between location and direction.
• Know how a compass works and how to use one.
• Know how to determine location using latitude and longitude.

Vocabulary

• compass
• compass rose
• direction
• elevation
• latitude
• location
• longitude
• relief
• sea level
• topography

Introduction

Without being able to pinpoint a location, understanding Earth’s surface would be of little value. Scientists, and even people on the move, must have a system to locate themselves and important features on the Earth.

Location

Perhaps you are sitting in the front office at Clovis West High School in California (Figure below). There are many ways to indicate your location, any of which can be used to find you.

1. Street address: 1070 East Teague, Fresno, California.
2. Latitude and longitude: 36.85926°N, 119.76468°W.
3. Triangulation: 168 miles from Santa Barbara, 122 miles from San Jose, and 24 miles from Auberry.

A triangulation map for Clovis West High School.

Any of these locations can be used and each has a different purpose. A postal worker might prefer to have a street address than to have to triangulate when delivering the mail. A geologist might want to know the latitude and longitude of an important feature. Triangulation is useful for locating where earthquakes and other things occur.

Direction

A line connecting two different locations has direction. Directions are expressed as north (N), east (E), south (S), and west (W) with gradations in between. Clovis West High School is north of Santa Barbara, east-southeast of San Jose, and southwest of Auberry. Direction is important for describing moving objects. For example, the wind may be blowing from southwest to northeast.

The most common way to describe direction in relation to the Earth’s surface is with a compass, a device with a floating needle that is actually a small magnet. The compass needle aligns itself with the Earth’s magnetic north pole, as demonstrated in the Figure below. A compass rose (Figure below) is a figure drawn on a map or nautical chart that shows directions or degrees.

(a) A compass is used to determine direction. A compass overlaid on a map can be used to show the directions the features are from each other. (b) This compass rose shows the major directions at 90 degrees and divides them into halves at 45 degrees – northeast (NE), southeast (SE), southwest (SW), and northwest (NW) – and then divides them in half again at 22.5 degrees – NNE, ENE, ESE, SSE, SSW, WSW, WNW, and NNW. Sometimes a compass rose just shows degrees.

Earth’s magnetic north pole is different from its geographic North Pole, known as true north. The geographic North Pole is the point where the axis upon which Earth rotates intersects the planet’s surface in the north. To find directions on a map using a compass you must correct for this discrepancy. The Figure below illustrates this offset between geographic and magnetic north.

Earth’s magnetic north pole is 11.5 degrees offset from its geographic north pole on the axis of rotation.

Latitude and Longitude

Any location on Earth’s surface — or on a map — can be described by latitude and longitude. Latitude and longitude are expressed as degrees that are divided into 60 minutes. Each minute is divided into 60 seconds.

Latitude tells the distance north or south of the equator. Latitude lines start at the equator and circle around the planet. The equator is the line that falls equally between the North and South Poles. The latitude of the equator is 0°. The North Pole is 90°N, with 90 degree lines in the Northern Hemisphere. The South Pole is 90°S, with 90 degree lines in the Southern Hemisphere (Figure below). The latitude of Clovis West High School (Figure above) is 36.85926°N expressed in degrees and fractions of degrees.

Longitude lines are circles that go around the Earth from north to south, like the sections of an orange. Longitude is measured perpendicular to the equator. The Prime Meridian is 0° longitude and passes through Greenwich, England. The International Date Line is the 180° meridian. The longitude of Clovis West High School is 119.76468°W expressed in degrees and fractions of degrees.

Lines of latitude and longitude form convenient reference points on a map.

An interactive globe from the Scripps Institution of Oceanography helps with orienting by longitude.

Since Earth is not flat, an accurate location must take into account the third dimension. Elevation is the height above or below sea level. Sea level is the average height of the ocean’s surface or the midpoint between high and low tide and is the same all around Earth. The topography of a region is the height or depth of that feature relative to sea level. Relief or terrain includes all the major features or landforms of a region. Figure below illustrates a topographic relief of California.

Topographic relief in California. Mt. Whitney is on the upper right, the highest point in the contiguous United States at 14,494 feet. Death Valley at -282 feet, the lowest contiguous point in the United States, does not appear in this figure but is SE of the Saline Valley, which it resembles.

Lesson Summary

• Location can be expressed in a variety of ways.
• Direction is useful for describing a moving object or the way to get between two locations.
• A compass needle aligns with magnetic north.
• Latitude indicates position north or south of the equator. Longitude indicates position relative to the Prime Meridian. Elevation is height above or below sea level.

Review Questions

1. What information could you use to describe the location of a feature on the Earth’s surface?
2. Give an example of a situation where you might need to describe which direction an object is moving.
3. What type of instrument can you use to tell the direction an object is moving?
4. What is topography?
5. What landforms are highest on the continents?
6. Explain what landforms on the continents are created by erosion by wind and water. How does erosion create a landform?
7. A volcano creates a new landform in Mexico. As the Earth scientist assigned to study this feature, explain how you would describe its position in your report.
8. Think about how you would draw a map to show all the different elevations around the area where you live. How might you create such a map?

Further Reading / Supplemental Links

• A good explanation of latitude and longitude is found at National Atlas.

Points to Consider

• How can a two-dimensional object, such as a map, express the features of an area in three dimensions?
• To locate yourself accurately, should you use a compass or a map?
• Why does California have such extreme relief?