Geography137
The Language of Maps
University ofMissouri-Columbia

Introduction to Map Types

Maps can be divided into three main classes, or types.

• General Reference Maps
• Thematic Maps
  and
• Charts

General ReferenceMaps

General reference maps are multi purpose maps. Their objective is to portray the spatial association of diverse geographical phenomena. Basically, general reference maps show a great deal of information! They are extremely useful in a variety of situations and they are the most common map type.

Examples of a General Reference Map are:

Road Map
USGS TopographicMap
Country Map

General reference maps answer basic questions such as:

Where is one thing in relationship to another?
Where are roads in relationship to urban areas?
Where are recrea tional areas in relationship to major metropolitian areas?
Where are rivers and streams in relationship to elevation and topographic data?

The list of questions is only limited by the types of information on the map and the spatial associat ions you can make using the information presented. Reference maps pay great attention to accuracy. Positional relationships of the mapped features are extremely important on this type of map. The location of roads, rivers, cities and other features are ca refully plotted.

Basically, reference maps illustrate a great deal of information and are used for just what their name indicates: REFERENCE

Thematic Maps

Thematic maps are d ifferent from general reference maps in that they focus on one topic or theme. The purpose of a thematic map is to show how this topic changes or differes from place to place.

Examples of a thematic map are:

Census Map
Trumpeter Swan Population Map
Agricultural Product Map
Weather Map

Positional accuracy, which is of the highest importance in reference maps, is less important for a thematic map. It is more important for the map user to pay a gre at deal of attention to what type of data was used to create the map and how the data was mapped on a thematic map. Questions such as, "What is the source of the data?", "What is the date the data was collected?", and "How was the data divided into mappable units?" must be asked by the map user in order to insure that the message the map is telling is accurate.

Charts

Maps designed for navigators are called charts. Simply put, maps are to be looked at and charts are to be worked on. Routes are plotted, positions are determined, bearings are marked on charts.

Examples of a chart are:

Nautical Chart
Aeronautical Chart

It needs to be emphasized that you can probably identify "pure" general reference maps, thematic maps and charts, but in many cases maps combine functions. For example the green printing on a topographic map shows the distribution of fo rested areas. Therefore topographic maps, deemed a general reference map, can also be a thematic map showing the distribution of forest areas in a region. Similarly, a thematic map can show political boundaries, cities, or rivers so that the map user can easily fix locations of the subject distribution.