AP Human Geography

## What a map is for A map is a selective picture of part of the Earth. The mapmaker decides what to show and what to leave out, so every map answers one kind of question better than others. Geographers sort maps into two broad groups according to the question they answer. A **reference map** shows where places and features are. Road maps, atlas maps of countries and cities, and maps of rivers and mountain ranges are reference maps: their job is to let you find a location, a boundary or a route. A **thematic map** shows the spatial pattern of one theme or variable, such as population density, average income, religion or rainfall. The place names and features are only there to anchor the pattern. Choosing a thematic map type depends on the kind of data and on what pattern the author wants a reader to see. ## Types of thematic map | Map type | How it shows data | Typical use | |---|---|---| | Choropleth | Areas such as countries, states or counties are shaded, with darker or lighter colors for higher or lower values | Rates or ratios by region, such as percentage of people over 65 or median household income | | Dot distribution | One dot stands for a set number of occurrences, so dots bunch where the thing is common | Where people, farms or a disease cluster or spread out | | Graduated symbol (proportional symbol) | Symbols such as circles change in size with the amount | Totals at a point, such as city populations | | Isoline | Lines join places of equal value | Elevation…