Map Basics

Meridians and Parallels

Lines are drawn on the globe to form a grid to help you locate places easier. Lines running parallel to the equator are called "parallels" or "lines of latitude." They're measured in degrees seventy miles apart and tell you how far north or south a place is away from the equator. The equator is at 0°. The North Pole is at 90° north of the equator, and the South Pole is at 90° south of the equator.

Meridians, or lines of longitude, are lines around the globe drawn from the North Pole to the South Pole. These also are measured in degrees. Each 15° represents an hour of rotation of the earth. The line through Greenwich, England is at 0°. Remember, this is the Prime Meridian. Any location east of the Prime Meridian is measured in degrees east up to 180° and is located in the Eastern Hemisphere. Likewise, any place west of the Prime Meridian is measured in degrees west up to 180° and is located in the Western Hemisphere.

You'll see this grid on all globes and most good maps. The grid provides a kind of "global address" for any location on earth. The N or S meridian degrees ( ° ) are given first, followed by the E or W degrees (°) of parallels. For example, Denver, Colorado is located at about 40° N 105° W. More precise directions include minutes ('). One minute equals one sixtieth of a degree. The more specific location of Athens, Greece, for example, is 38° N 23° 44'E. (This is read thirty-eight degrees north, twenty-three degrees, forty-four minutes east.) Take a moment to check this in your own atlas.

Finding Your Way Around

Did you find Athens in your atlas? If you can't find your way around in an atlas, that's about to change! If you don't already have it handy, stop and get an atlas now and take this quick lesson. Open the atlas to the back section called the gazetteer, or index. The gazetteer lists all places referenced in the atlas in alphabetical order. It will give the "global address" or a grid location and the page number where the place can be found.

For practice, look up Athens, Greece in the gazetteer. Note page number and location. Your atlas may list a reference labeled 1, 2, 3...or A, B, C...This is a grid reference. Turn to the page indicated, look for the grid on the map, and follow the path where the letter and the number cross. That's the grid section where you'll find Athens. If you're looking for the "global address" of a place and your atlas doesn't give it in the index, you can figure it out yourself to a pretty close degree of accuracy. Look up the place given in the grid reference, and locate the latitude and longitude referenced on its borders.

The location in your gazetteer may say "38°N 23° 44'E ". If you know the longitude and latitude of a place you can find it on a map in the same manner. Using Athens again, find the right page. Locate approximately 38°N from the side border of the map (remember, this tells you that Athens is north of the equator by 38°). Now, locate approximately 23° at the top of the map. If you trace both those lines across and down, your two fingers should bump into each other right at Athens, Greece.

Knowing Your Legend or Key

Do you have a clear picture now of longitude and latitude and how they're marked on a map? What else is on a map besides grids? All of the different pieces of information on a map are represented by symbols. The symbol doesn't necessarily look like what it represents, so they're shown in the legend, a separate box on the page with information about the map. Symbols could include a series of dots, dashes, dashes and dots, thin lines, thick lines, color lines, circles, triangles. The legend will include the scale, distance, and what each of the symbols represent. The scale is usually written in a representative fraction, such as 1:10,000. The first number represents the unit on the page, and the second number represents the unit on the ground. In the USA, map scales usually represent inches. In this case, one inch on the map equals 10,000 inches on the ground.

There are many different types of maps to meet many different needs. Maps can be divided into two groups: general reference maps and thematic maps.

General Reference Maps

General reference maps show general information such as countries, continents, cities, rivers, elevation , political and other features. These maps are found in encyclopedias, textbooks or in an atlas. Road maps are a type of general reference map that shows the kinds of roads and distances to help travelers choose the best route for their journey. Pilots use reference maps called "charts" to plan their course of travel.

Special Maps or Thematic Maps

Special maps which focus on political boundaries are called political maps. A political map shows the political divisions of an area, such as countries, states, counties and cities. It may also include basic physical features, such as rivers or lakes. Many maps use different colors to represent each nation; others use different types of lines or dots and dashes to distinguish between borders.

Physical maps emphasize the general roughness of the surface of the earth. Color is used to indicate elevation, and shading may also indicate land forms and other features of the earth's surface as seen from an airplane or satellite photograph.
Topographic maps are special maps designed to show accurately the contour of the earth's surface. Contour lines indicate elevation or steepness of hills, mountains, or valleys, and show rivers, ponds or any other body of water. Topographic maps are used by campers, hikers, hunters, or fire and rescue crews to plan their journey on foot.

Other special or thematic maps emphasize some particular feature, using color, shading, or symbols to represent differences. "Population density maps" show how many people per square mile live in the area. "Rainfall maps" show average yearly rainfall of a selected area. "Weather maps" use symbols to show weather patterns. "Product maps" are labeled with text, color, or symbols to demonstrate the type of products produced in an area.

Illustrated Maps

An illustrated map is a special map that shows an area graphically (a drawn picture). You've probably used one at the amusement park to find your way around. A Chamber of Commerce may provide illustrated maps depicting the city's downtown, including three dimensional pictures of buildings and other landmarks. Illustrated maps aren't usually drawn to scale, but are useful for finding your way around a smaller area. (Good for the mall, not Texas!)