What Is a Map?
A map is a flat, two-dimensional representation of part of the Earth's surface, viewed from above. Maps reduce the real world to a manageable size using a scale, and use symbols, colours, and lines to represent features of the landscape.
Maps are used for:
- Navigation and finding routes
- Understanding landforms and landscapes
- Planning buildings, roads, and cities
- Military and emergency services
- Weather forecasting
Types of Maps
| Map type | What it shows |
|---|---|
| Political map | Country borders, capitals, cities |
| Physical map | Landforms, rivers, mountains, seas |
| Topographic map | Detailed landscape features, contour lines, elevation |
| Road map | Roads, motorways, towns |
| Climate map | Climate zones, rainfall, temperature |
| Population map | Where people live; density |
The Key (Legend)
All maps have a key (also called a legend) — a panel that explains what each symbol, colour, and line on the map represents. Without the key, a map is difficult to interpret. Common symbols include blue lines for rivers, green areas for forests, and dots for towns.
The first known maps date back to ancient Babylonia (around 2300 BCE) and ancient Greece. The Greek mathematician Eratosthenes (~276–194 BCE) created a map of the known world and also calculated the circumference of the Earth with remarkable accuracy — achieving a result within about 2% of the modern accepted value, without any modern technology.
Contour Lines
Contour lines are lines on a map connecting points of the same height (altitude) above sea level. They are used on topographic maps to show the shape and steepness of the land.
Rules for reading contour lines:
- Each line represents a specific height (e.g. every 10 m).
- Closely spaced contour lines = steep slope.
- Widely spaced contour lines = gentle slope.
- Closed circles/ovals = a hill or mountain top.
- Contour lines never cross each other.
A useful trick for understanding contour lines: imagine the water rising slowly in a landscape. Each contour line is like a water line — the circles close around hills as "water level" rises higher. Where the lines are bunched closely together, the slope is steep (the water level rises quickly). Where they are spread apart, the land is nearly flat.
Other Map Features
- Spot heights: A dot with a height number showing the exact elevation at a specific point.
- Colours: Blue for water, green for lower land, brown/yellow for higher land, white for very high (snow-capped) regions.
- Grid lines: Help locate features with a grid reference.
- North arrow / compass rose: Shows which direction is north on the map.
Real world: Eratosthenes and the first scientific map
Around 240 BCE, Greek mathematician Eratosthenes created one of the earliest scientific world maps — and calculated Earth's circumference to within 2% accuracy using only shadows and geometry. He knew that at noon on the summer solstice, the Sun was directly overhead in Syene (modern Aswan, Egypt) while in Alexandria it cast a shadow at an angle of about 7.2°. Using the distance between the two cities, he calculated Earth's circumference as approximately 40,000 km. This is extraordinarily close to the modern accepted value of 40,075 km — achieved without satellites or computers.
Real world: Google Maps and OpenStreetMap — digital mapping today
Google Maps is used by over 1 billion people monthly and covers every road, building, and trail on Earth. It was created using satellite imagery, aerial photography, and crowdsourced data. However, it has limitations — rural areas of low-income countries are less detailed, and recent changes may not yet be mapped. OpenStreetMap (OSM) is a free, community-edited alternative used by humanitarian organisations. After the 2010 Haiti earthquake, hundreds of volunteers used OSM to map roads and buildings within days, allowing rescue teams to navigate a country with almost no pre-existing digital maps.
Real world: Navigation before GPS — merchant shipping
Before GPS (widely available from the 1990s), ship navigators used paper charts, compass bearings, and a technique called dead reckoning — estimating position based on known speed, direction, and elapsed time. A navigator crossing the Atlantic would take star sightings with a sextant, plot positions on paper charts, and use tidal maps to adjust for ocean currents. A single error in reading the chart could lead a ship hundreds of kilometres off course. The sinking of RMS Titanic in 1912 was partly a navigation failure — the ship's charts did not show all the iceberg hazards in that area.
Where do you see this in real life? The next time you use Google Maps or a hiking app, try switching to "terrain" or "topographic" mode — you will see contour lines and elevation shading. Compare a flat area (like a city centre) with a hilly area (like a national park) and notice how different the contour patterns look. This is the same information on paper OS maps, just displayed digitally.
Practice Problems
On a topographic map, two hills are shown — Hill A has contour lines spaced close together, and Hill B has contour lines spaced far apart. Which hill has steeper slopes? Explain.
Show answer
Why is the key (legend) an essential part of a map?