GEOG 160
Mapping Our Changing World

3.4 Glossary


Aggregation: The process of combining multiple features into one.

Average: A measure of central tendency, specifically the mean value calculated as a total amount divided by the number of entities producing the amount.

Cartographic Process: A cyclic process linking data from the environment as inputs, the final map as an output, as well as the map maker and map user as the creator and consumer of the map.

Cartography: The academic and professional field focused on mapping.

Choropleth Map: A map that depicts quantities aggregated to their regions (often called “enumeration units”) by filling the entire region with a shade or color.

Count: Whole numbers that represent the individual data such as people or housing units.

Delete: Systematically removing data to better serve the purpose of the map such as map legibility.

Density: A count divided by the area of the geographic unit to which the count was aggregated.

Dot Map: Maps that depict magnitude by frequency rather than size of symbol and add the depiction of geographic distribution by use of the graphic variable of location. Specifically, dot maps assign one to many dots per enumeration area to represent a specific count in each area.

Enumeration Areas: Areas or regions in which quantitative data is aggregated to (e.g., census tracts, counties, states, etc.).

Equal Interval: A data classification scheme that divides the data into equal sections (intervals).

Graphic Variables: Primitives in which map symbols are constructed. The core graphic variables include location, size, shape, orientation, texture, and three components of color – color hue (red, green, blue, etc), color lightness (how light or dark the color is), color saturation (how pure the color hue is).

Map Abstraction: The process of representing the real world in simplified form in order to generate a more legible map. It includes at least five major (interdependent) steps: (a) selection, (b) classification, (c) simplification, (d) exaggeration, and (e) symbolization.

Percent: The proportion of a total ranging from 0-100%.

Proportional Symbols: Symbols in which the graphic variable of size is used to depict data magnitude. There are two types of point features typically depicted: features where data represents a geographic position directly and features that are geographic areas to which data are aggregated and the data magnitudes are assigned to a representative point within the area.

Quantile: A general label for any grouping of rank ordered data into an equal number of entities; quantiles with specific numbers of groups go by their own unique labels ("quartiles" and "quintiles," for example, are instances of quantile classifications that group data into four and five classes respectively).

Rate: A quantity that tells us how frequently something occurs, where a value is compared to a standard value.

Reference Map: A map with a main purpose to act as a reference. The prototypical reference map depicts the location of “things” that are usually visible in the world.

Smoothing: The act of eliminating unnecessary elements in the geometry of features, such as the superfluous details of a nation’s shoreline that can only be seen at a larger, zoomed in regional scale.

Thematic Map: A map typically depicting “themes,” generally more abstract, involving more processing and interpretation of data and often representing concepts that are not directly visible; examples include maps of income, health, climate, or ecological diversity.

Typification: A depiction of the most typical components of the mapped feature.