AP® Human Geography review sheet from Aim for Five (aimforfive.com/geo/units/1/1-1)
Unit 1 · Topic 1.1
1.1 Introduction to Maps
Maps are the main tool geographers use to show where things are and how places relate. You need to tell reference maps from thematic maps, read the spatial patterns a map shows, and explain why every map projection gets something wrong.
Key terms
- reference map
- thematic map
- map projection
- absolute vs. relative distance
- absolute vs. relative direction
- clustering vs. dispersal
Reference maps and thematic maps
A reference map shows where things are. Road maps, political maps of countries and capitals, and topographic maps (which show the shape and height of the land) are all reference maps. You use them to find your way or locate a feature.
A thematic map shows the pattern of one topic across space, such as population density, median income or the share of people who speak Spanish. On the exam, most maps you're given are thematic, and the question is usually about the pattern they reveal.
| Thematic map type | How it shows data | Example |
|---|---|---|
| Choropleth | Shades or colors whole areas, like states or counties, by value | Median age by state |
| Dot distribution (dot density) | Each dot stands for a set number of something | One dot per 10,000 people |
| Graduated symbol | Bigger symbols mean bigger values at a point | Circles sized by city population |
| Isoline | Lines connect points with equal value | Contour lines of elevation, or temperature lines |
| Cartogram | Resizes each area by its data value instead of its land area | Countries drawn by population size |
Patterns a map can show
- Absolute distance: distance measured in standard units, like 300 miles or 480 kilometers.
- Relative distance: distance described by time, cost or connection, like “a 20-minute drive” or “one stop on the train.” Two places 300 miles apart can be relatively close if a fast rail line links them.
- Absolute direction: the cardinal directions, north, south, east and west.
- Relative direction: direction described from a point of view, like “left,” “up north” or “out West.” Terms like “Far East” only make sense from Europe's point of view.
- Clustering: things are grouped close together, like coffee shops downtown.
- Dispersal: things are spread out, like farmhouses across the rural Great Plains.
- Elevation: height above sea level. Topographic maps show it with contour lines; lines packed close together mean steep land.
Map scale
Map scale is the ratio between distance on the map and distance on the ground. A scale of 1:24,000 means 1 inch on the map equals 24,000 inches on the ground. A large-scale map shows a small area in a lot of detail, like a city neighborhood. A small-scale map shows a big area with little detail, like the whole world. It feels backwards, so remember that 1:24,000 is a bigger fraction than 1:10,000,000.
Don't confuse map scale with scale of analysis (topic 1.6), which is about whether you study a pattern at the local, national, regional or global level.
Why every projection distorts
A map projection is a method for drawing the round Earth on a flat surface. You can't flatten a sphere without stretching or tearing it, so every flat map distorts at least one of four things: shape, area, distance or direction. Mapmakers choose which distortion to accept based on what the map is for. Maps are also selective: the mapmaker decides what to include and leave out, so no map is neutral.
| Projection | What it keeps | What it distorts |
|---|---|---|
| Mercator | Shapes of small areas, and true compass direction (straight lines are constant bearings) | Area, badly, toward the poles; Greenland looks about as big as Africa, which is roughly 14 times larger |
| Gall–Peters | Area (equal-area) | Shape; land near the equator looks stretched top to bottom |
| Robinson | A compromise with no extreme errors | A little of everything, especially near the poles |
| Goode homolosine | Area, with good continent shapes | It is interrupted, so oceans are split and distances across the gaps can't be measured |
Worked examples
Try each one yourself first, then open the solution.
- Example 1
Explaining a projection's limitation
A student uses a Mercator world map to argue that Greenland and Africa are about the same size. Explain why the map is misleading for this purpose.
Show the solutionHide the solution
- Step 1: Name the property the Mercator projection keeps: it preserves direction and local shape, which made it useful for sea navigation.
- Step 2: Name what it sacrifices: area is stretched more and more as you move away from the equator.
- Step 3: Apply it to the case: Greenland is far north, so it is enlarged a lot, while Africa straddles the equator and is barely stretched.
- Step 4: Finish with the correct comparison and a better tool: Africa is about 14 times larger, and an equal-area projection such as Gall–Peters should be used to compare sizes.
Answer: The Mercator projection keeps directions true but enlarges areas toward the poles, so high-latitude Greenland looks far bigger than it is compared with equatorial Africa. Africa is actually about 14 times larger; an equal-area projection would show this correctly.
Common mistakes
- Calling a world map a large-scale map. A world map is small-scale because it shows a huge area with little detail.
- Saying a projection “has no distortion.” Every flat map distorts something; say which property it protects and which it sacrifices.
- Mixing up clustering and density. Clustering describes how things are arranged relative to each other, while density is how many there are per unit of area.
On the exam
- Expect multiple-choice questions that show a thematic map and ask you to name the map type or describe the pattern, such as clustering along a coast.
- In free response, when you describe a pattern on a map, name where it is high, where it is low, and give a specific place from the map.
Connected topics
Videos
Check yourself
4 questions on 1.1 Introduction to Maps. Pick an answer to see if you got it, and why.
On a Mercator projection, Greenland appears roughly the same size as Africa, although Africa's land area is about 14 times larger. Which of the following best explains this distortion?
A researcher wants a world map that compares the amount of land devoted to farming in Canada, Brazil and the Democratic Republic of the Congo. Which type of projection would be most appropriate?
A student wants to show the population of the 50 largest cities in Brazil on a single map so that a reader can quickly see which cities are biggest. Which map type would work best?
A map of a mountain range has curved lines; every point on each line is at the same height above sea level, and the lines bunch tightly together on one side of a peak. What does the tight bunching most likely indicate?
0 of 4 answered