Kids' Hangout

Budding Geographers

Q: How are maps made?

A: This is a complicated question and we can't answer it completely here. We'll just point out some highlights.

People who create maps are called cartographers. The first thing a cartographer does is to decide what to show in the map. A photo shows everything in front of the camera. A map shows only what we want it to show. So the cartographer must first spend some time thinking about that.

The next task is to find sources of information. Where are the coast lines? Where do the rivers run? The roads? In the past we had libraries of "base maps" containing these details, and we'd trace those lines on to the new map, then add the details we wanted to show. Today computers store our base maps; we have to decide on the scale and the amount of detail.

Of course this raises the question: how was the base map created? That's a long story, and we'll cover it some other time.

There are many kinds of maps. Some are for tourists and visitors; they show roads and important buildings. Some are for scientists; they may show temperature and rainfall. Today, using computers, we can make maps much more easily, so we use them to show just about anything: houses for sale, the amount of traffic, crime statistics, the route to Grandma's house. These are called thematic maps because they focus on a theme. The biggest challenge in making thematic maps is to get the data right, and to convey the right message to the viewer. This takes a lot of training.

Drawing the map used to be very laborious. Cartographers would spend hours with pens and etching knives, creating drawings in mylar (plastic) layers, one for each color, and stenciling the text or sticking it on. Today this is done entirely by computer. Up to the 1980s, computers used pens and ink too; they would dart around the paper drawing the same things humans did, only much faster. Today laser printers do much of this. They draw the lines, print text, and color the areas, and so maps can be created quite fast. Some of the most useful maps are created only on computer screens and are never printed. It still takes cartographers to decide the color and thickness of lines, what to place in the center and on the periphery.

As we push into the future, we're starting to deal with maps that change in front of our eyes. For example, maps showing population growth. The animated weather maps on TV. The GPS navigation screens in cars. These maps can be very difficult to design, because the cartographer never quite knows what they'll have to show; and they have to be re-drawn, sometimes several times a second. So modern cartographers have to think carefully about what map viewers need, how to place items on the map with just the right amount of detail, and how to put the right label on things in such a way that they don't run into each other. Cartographers now have to know a fair bit about computers and how to organize the information so that the computers can get the job done fast.