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:

Types Of Map Symbols
Symbol Meaning
River Map Symbol River
Railroad Tracks Map Symbol Railroad Tracks
Food Map Symbol
Food
Bar Map Symbol Bar
Cafe Map Symbol Cafe
Shopping Map Symbol Shopping
Grocery Map Symbol Grocery
Arts Map Symbol Arts
Lighthouse Map Symbol Lighthouse
Theater Map Symbol Theater
Tourist Attraction Map Symbol Tourist Attraction
Casino Map Symbol Casino
Aquarium Map Symbol Aquarium
Event Venue Map Symbol Event Venue
Amusement Park Map Symbol Amusement Park
Historical Site Map Symbol Historical Site
Museum Map Symbol Museum
Movie Theater Map Symbol Movie Theater
Monument Map Symbol Monument
Music Map Symbol Music
Relic Map Symbol Relic
Gas Station Map Symbol Gas Station
Parking Map Symbol Parking
Car Rental Map Symbol Car Rental
Hotel Map Symbol Hotel
Resort Map Symbol Resort
ATM Map Symbol ATM
Bank Map Symbol Bank
Hospital Map Symbol Hospital
Pharmacy Map Symbol Pharmacy
Medical Map Symbol Medical
Park or Forrest Map Symbol Park / Forest
Mountain Map Symbol Mountain
Sports Stadium Map Symbol Sports Stadium
Zoo Map Symbol Zoo
Campground Map Symbol Campground
Cemetary Map Symbol Cemetary
Golf Course Map Symbol Golf Course
Garden Map Symbol Garden
Hiking Map Symbol Hiking
Boating Map Symbol Boating
Fishing Map Symbol Fishing
Airport Map Symbol Airport
Train Map Symbol Train
Metro Map Symbol Metro
Subway Map Symbol Subway
Bus Map Symbol Bus
Rail Map Symbol Rail
Ferry Map Symbol Ferry
Bridge Map Symbol Bridge
Civic Building Map Symbol Civic Building
Post Office Map Symbol Post Office
Library Map Symbol Library
Police Station Map Symbol Police Station
School Map Symbol School
Restroom Map Symbol Restroom / Bathroom
Miscellaneous Map Symbol Miscellaneous
Church or Temple Map Symbol Church or Temple
Synagogue Map Symbol 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.

[From https://lh3.googleusercontent.com/proxy/a1wS_pdf4Akt6OKRNom-60unYf-V2GiW-zEFn9VAfwi_1VvVkLoaIDFymGj4APohfG2krRZdGbXFCzXM-NjkBmvFUnBTyPFYP_J8RE1fpUcgCwM]

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.

[From https://i.pinimg.com/originals/74/8c/10/748c10612457c8a78f9130c958351696.jpg]

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.

Map Key Quiz

See if you can find your way around a map by answering these questions.

  1. Define the “map key.”
  2. What is another name for a legend on a map?
  3. Why is a legend necessary for most maps?
  4. What symbol is next to Washington DC on the map?

[insert copyright-free version of U.S. map such as this one with Washington, DC starred from https://geology.com/world/the-united-states-of-america-satellite-image.shtml]

  1. What does a star usually mean on a map?
  2. Fill in the blank: a map's ___________ explains its markings and symbols.
  3. What map symbol for a mountain range is most often used?

The key to becoming a legend in your own time is to study hard. Don’t peek at the answers below until you have tried your best!

  1. You might define “map key” as the part of a map inside the map legend that tells what the map symbols mean. We use a map key and map legend interchangeably. 
  2. Another name for a legend on a map is a map key, although you can get very picky and say that the legend holds the map key and other information.
  3. A legend is necessary for most maps because cartographers cannot write everything into the map, so they need symbols. The symbols require a key to understand them.
  4. The star symbol, ★, is next to Washington DC on the map.
  5. A star, ★ , usually means a country capital on a map.
  6. Fill in the blank: a map's legend or key explains its markings and symbols.
  7. The map symbol for a mountain range is often a tiny triangle or upside-down : or .

What you learned:

After working your way through this lesson and video, you have learned the:

  • Definition of a map key and a map legend
  • Purpose of a map key in the map legend
  • Types of symbols on a map
  • Difference between a map key and map legend
Instructor: Malcolm M.
Malcolm has a Master's Degree in education and holds four teaching certificates. He has been a public school teacher for 27 years, including 15 years as a mathematics teacher.

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