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# Map

A map is a symbolic representation of selected characteristics of a place, usually drawn on a flat surface

3 - 12+

### Subjects

Geography, Geographic Information Systems (GIS)

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## Learning materials

### Maps

A map is a very useful tool. It can show the shapes of countries. It can show a single city's streets. Or, it can show the height of mountains. It depends on the type of mapMapmakers are known as cartographers.

Scale

Relative distances on a map should be more or less the same as in real life. Suppose a real-life road is five times as long as another road. On a map, those roads should have the same relative distance. The line that represents one road should be five times as long as the other one.

Maps usually have scales. A scale says how small things on a map are compared to the real world. For example, one inch on the map might be 1,000,000 inches, or more than 15 miles, in the real world. A scale might say this in words. It could also use numbers, like 1:1,000,000. Some maps use a visual scale. A visual scale looks like a ruler. It is a line marked off in miles or kilometers.

Symbols

A symbol is something that stands for something else. Cartographers use symbols to stand for geographic features. For example, black dots represent cities. Circled stars represent capital cities. Different sorts of lines represent roads, highways, and rivers.

Colors are used as symbols, too. Green is often used for forests. Tan is used for deserts. Blue stands for water. Some maps also show height. The lines that show height are called contour lines. They tell you if a part of the land, like a crater, sinks into the ground. They also tell you if there's a mountain that rises up.

To help people understand what all the symbols mean, maps usually have a legend. The legend shows a list of symbols and explains them. It also shows the scale of the map.

Grids

Many maps have grids. A grid is made of two sets of straight lines that cross each other. By crossing, they create squares, or boxes. A map's grid helps people find specific places.

The lines of a grid are called latitude and longitude lines. Both kinds of lines run across the map. Latitude lines run east-west. They are parallel to the Equator. The Equator is an imaginary line around the middle of Earth. Longitude lines run north-south.

Latitude and longitude are not real lines. They just make it easier to read the map. The points where they cross are called coordinates. These coordinates are used to give the exact location of a place.

Maps of smaller areas usually use letters and numbers. The letters run across the top of the map. The numbers run across the left side. Each box in the grid has both a letter and a number. This helps users find things on the map. For example, suppose you want to find a particular park. First, you look at the map's index. An index is a list of all the places shown on a map. It appears on the bottom or back of a map. Say the index gives the park's location as B4. You would look in the box where column B and row 4 cross each other. The park would be right in that box.

Map Projections

Earth is spherical, or ball-shaped. Most maps are flat. The difference causes problems for cartographers.

To understand why, think of a globe. A globe is a spherical copy of Earth. It shows the shapes of continents and islands. It also shows the location of cities.

Now, suppose the globe is cut in half. Then, suppose each half is flattened out into a map. Now, all the shapes are distorted. Things no longer appear as they really are. Relative sizes, shapes, and locations have changed.

Every map has some sort of distortion. The larger the area covered, the greater the distortion. Size, shape, and distance can be measured accurately on Earth. However, they cannot all be shown correctly on a map at the same time. For example, a map can keep the correct sizes of land masses. It can keep the correct shapes of very small areas. It cannot keep both, though.

Cartographers have to decide what to change and what to keep. Usually, their choice depends on the kind of map they are making. The way they show the spherical Earth on a flat map is called a projection. Each projection makes things look different. Each is useful in different ways.

One type of projection is called planar. Imagine touching a globe with a flat piece of cardboard. Now, imagine that every part of the globe jumps straight out of the globe and onto the cardboard. The cardboard now has a flat image of Earth. This is the planar projection.

Planar projections are most accurate at the center. In our example, that is where the cardboard touches the globe. These projections are often used to show the North or South Poles.

Another type of projection is conical. Imagine wrapping a cone around Earth. The point of the cone should be above one of the poles. Like before, take all the parts of Earth and map them onto the cone. Now, you can unroll the cone into a flat map. You have a conical projection. In conical projections, the most accurate areas are between the Equator and the poles.

Finally, we have cylindrical projections. Imagine that Earth's surface is projected onto a tube. This tube is wrapped around the globe. Usually, the tube would touch the globe along the Equator. Then, cut open the cylinder and flatten it into a map. The regions near the Equator are the most accurate. Regions near the poles are the most distorted.

People who make measurements in order to create maps are called surveyors. They measure the size, shape, and location of a piece of land. Today, many surveyors use remote sensing. Sensors are attached to airplanes or space satellites. These sensors collect geographic information from above.

Cartographers used to draw maps by hand. Today, most maps are made with computers. Cartographers make different types of maps. They can be divided into two main categories.

The first type is a general reference map. This type of map shows general geographic information about an area. It includes the locations of cities, boundaries, roads, mountains, rivers, and coastlines. It could also be a topographic map. That means it shows changes in height. It shows all the hills and valleys in an area.

The second type of map is a thematic map. It shows information about people, animals or concepts. For example, one thematic map might show where people speak a certain language. Another might show how much people earn in different parts of the country.

History of Mapmaking

Maps have been around for a very long time. The earliest ones were just scratched in the dirt. One of the oldest existing maps was found in Spain. It was carved in stone 14,000 years ago.

The ancient Greeks were the first to create scientific cartography. They knew the size and shape of Earth. Much of what they learned was forgotten, though. In the Middle Ages, maps in Europe were very inaccurate.

The Arabs were able to keep the knowledge of scientific cartography. They made the first accurate globe of the Western world. In Europe, maps only started getting better in the 1400s. By then, European sailors were traveling around the world. They mapped the new lands they discovered. By the 1800s, world maps became much more accurate.

Fast Fact

Beyond Earth
Using images taken from spacecraft, cartographers have created detailed maps of the surfaces of the moon and Mars. Astrocartographers have identified martian valleys, craters, and even dry riverbeds.

Fast Fact

Eratosthenes
Eratosthenes was an astronomer, librarian, mathematician, and poet. He also invented the discipline of geography in his spare time. Using the position of the sun, Eratosthenes was able to calculate the circumference of Earth without leaving Egypt, his home. He used the length of a stadium as his unit of distance. Because stadiums came in two different sizes in the world of ancient Greece, and we don't know which stadium Eratosthenes used, we can't know exactly what he calculated for the circumference of Earth. If he used the larger Greek stadium, his circumference would be larger than Earth by about 16 percent. If he used the smaller, so-called "Egyptian stadium," his calculation would still be largerbut only by 1 percent.

Fast Fact

A type of cylindrical projection called a Mercator projection shows direction well. It was long used to make charts that sailors could use to find their way around the globe. Like all cylindrical projections, a Mercator projection greatly distorts the size of land near the poles. In a Mercator projection, Greenland and Africa are about the same size. In reality, Africa is 14 times the size of Greenland.

Fast Fact

Printing Pioneers
The Chinese were skilled cartographers. The first map was printed in China in 1155 C.E., some 300 years before maps were printed in Europe.

###### Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Jeff Hunt
Hilary Hall
Hilary Costa
Erin Sprout
Santani Teng
Melissa McDaniel
Diane Boudreau
Tara Ramroop
Kim Rutledge
###### Illustrators
Mary Crooks, National Geographic Society
Tim Gunther
###### Editors
Jeannie Evers, Emdash Editing, Emdash Editing
Kara West
Nancy Wynne
###### Producer
National Geographic Society
###### Last Updated

February 20, 2024