Map key definition
A map key is an inset on a map that explains the symbols, provides a scale, and usually identifies the type of map projection used. Technically, the key is part of the map legend. The key explains the symbols while the legend holds the key and other information.
Purpose of a map key
The purpose of a map key is to tell you the meaning of the symbols on a map. The key on a map interprets each symbol so that you can read and understand the map.
For example, what does this symbol, ⇞, mean? Is it important to know what it means? Is it pointing in a direction, standing for a single tree, or indicating a forest?
The map key is the only way for you to know for sure what the above symbol means.
Map key symbols
When making a map, Cartographers (map makers) cannot write out everything and make it fit. They need quick, simple drawings, called map symbols, to replace written information. If you do not know what ⋅, ∘, or ⊙ means, you cannot understand the map.
A map key tells you what all the symbols on the map mean. For example, the small black dot, ⋅, means a town or village, the open circle, ∘, means a city of at least 75,000 people or that ⊙ means a state capital. A map key can tell you that ★ usually shows a country’s capital.
Every map uses its own map symbols, depending on the information the cartographer wants to show. Map keys can show symbols for natural resources, population centers, bodies of water, types of industry, and much more.
Here are some different symbols appearing in map keys:
| Symbol | Meaning |
|---|---|
| River | |
| Railroad Tracks | |
| Food | |
| Bar | |
| Cafe | |
| Shopping | |
| Grocery | |
| Arts | |
| Lighthouse | |
| Theater | |
| Tourist Attraction | |
| Casino | |
| Aquarium | |
| Event Venue | |
| Amusement Park | |
| Historical Site | |
| Museum | |
| Movie Theater | |
| Monument | |
| Music | |
| Relic | |
| Gas Station | |
| Parking | |
| Car Rental | |
| Hotel | |
| Resort | |
| ATM | |
| Bank | |
| Hospital | |
| Pharmacy | |
| Medical | |
| Park / Forest | |
| Mountain | |
| Sports Stadium | |
| Zoo | |
| Campground | |
| Cemetary | |
| Golf Course | |
| Garden | |
| Hiking | |
| Boating | |
| Fishing | |
| Airport | |
| Train | |
| Metro | |
| Subway | |
| Bus | |
| Rail | |
| Ferry | |
| Bridge | |
| Civic Building | |
| Post Office | |
| Library | |
| Police Station | |
| School | |
| Restroom / Bathroom | |
| Miscellaneous | |
| Church or Temple | |
| Synagogue |
As you see in this list of Google Maps symbols above, different colors represent different categories. Green for outdoors, orange for dining and drinks, etc.
Map key examples
This map of Tennessee has a key that shows how the land is used. Tiny symbols that look like pigs, plants, and stone show where animals are raised for food, where plants are grown, and where ores and rocks are mined.
This map key uses natural colors for natural formations but uses abstract shapes for human activity. It uses coded squares to show ruins and archeological sites. It uses circles to stand for villages and towns. The natural formations such as ice and desert are shown in colors that resemble the real things.
Legend vs. key
You may wonder what the difference is between a map key and a map legend. The key makes the map understandable. The map legend usually includes not only the map key to the symbols but a lot of other useful information:
Map scale, in large units like miles and kilometers, or small units like feet and meters
Map projection name, like Mercator, Cassini, Equirectangular, Gauss–Krüger, or Sinusoidal
Map publication date
Cartographer or company name
Today we use both phrases to mean the same thing, but the map key is technically found in the map legend.
Compass rose on a map
The compass on a map is called a compass rose. Its main function is to point north, but it almost always shows the cardinal directions (north, south, east, and west). Sometimes it tells the intermediate or ordinal directions, too: northeast, southeast, northwest, southwest.
Unlike all the other symbols on the map, the compass rose does not usually appear in the key or legend. It is usually drawn in an unimportant area, like an ocean or vast desert, so that it does not cover locations. By tradition, most maps orient so that north is at the top of the map.
On maps and nautical charts dealing with tides, sailing, and coastlines, the compass rose is also called a "windrose" or "rose of the winds." Highly accurate nautical charts and some topological maps show both true north and magnetic north on the compass rose.
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