Most of us carry in our heads simple maps of our surroundings. We use them to get from one place to another, as well as to navigate our way around safely or appropriately for whatever activities we engage in at various stages of our lives. These maps are called mental maps and are not generally drawn on paper. Think for a minute of the kinds of things that would feature in your own mental map of the way you get from home to school.

These features will all have some significance for you, but do you think they would necessarily mean much to someone else? Would other people, especially those unfamiliar with your local area, be able to follow your mental map?

What if your activities revolved around something as different as land development and political activism, or around religious practice, visiting art galleries, purchasing cattle, needing help from social services or drug-taking and gambling? Might your age, health, income, social status or family background and belief system affect your choice of which features were significant? How would you represent the area you lived in? What do maps say about how we live and what we value? What different kinds of mental maps do we have and need in our lives?

Only we ourselves really understand most of our mental maps, even when they are written down. To help to overcome this problem and to keep a record of our surroundings, people have been using and making a variety of different maps for thousands of years.

Historical development and political factors have also played a role in cartography (mapmaking). How would you draw a map of the world as you know it if you only knew that a small part of the world existed or had any relevance for you? What if you were a leader of old who wanted your kingdom's mapmakers to use a map as propaganda, to make your kingdom look larger and more powerful than that of another that you wanted to control or subdue?

Even when it tries to be true observable facts, cartography can be technically very difficult and problematic. This is certainly true when cartographers try to accurately represent a three-dimensional planet on a flat surface. Compare the Mercator projection with Peter's, Mollweide's or Robinson's projections, for instance, and you will notice that different perspectives and distortions are created. (You will be able to do this in Internet Investigation.)

The tools of the cartographer have always been important. Instruments such as the astrolabe, compass, knotted ropes and reliable clocks have all played a significant role in the mapmaking task. Today, cartography is a high-tech task and it often involves studying at University or TAFE. Computer-based Geographic Information Systems (GIS) are used in conjunction with remote sensing data collected by satellites. The information can be stored and manipulated by computers to produce 3-dimensional maps or maps based on any place in the world.

First, a map is an abstraction of the reality perceived by the cartographer or the person or country or organisation for whom the map is made. Second, the cartographer selects only the information that is essential to fulfil the purpose of the map and that is suitable for its size and scale. Maps use symbols such as points, lines, area patterns and colours to convey information.

Maps enable us to:

1. locate places on the surface of the earth
2. show patterns of distribution (of wealth, population, etc)
3. illustrate relationships between different phenomena.

In order to make maps we need know what features we are looking at and how far away from each other they are. To make the map accurately, we need to take into account three things:

• Map scale: This is the relationship between distances on a map and the corresponding distances on the earth's surface. It is expressed as a fraction or a ratio.
• Coordinate systems: These are numeric methods of representing locations on the earth's surface. The most commonly used coordinate system today uses latitude and longitude—angle measures expressed in degrees, minutes, and seconds. At larger scales, such as that of the region around your school, grid references may be used to locate places.
• Map projection: This is a function or transformation which relates coordinates of points on a curved surface to coordinates of points on a plane. (Various projections are discussed briefly above.)

By completing the worksheets and research activities in this eAtlas Update you will gain a much better understanding of the world of the cartographer.