Vocabulary

2.1 Understanding Maps

Dynamic Maps

Changeable or interactive representations of the earth. Dynamic mapping refers more to how maps are used and delivered to the map user today (e.g., online, via mobile phone) than to the content of the map itself.

Overlay

To lie on top of.

Reference Map

A map that delivers location information to the map user.

Thematic Map

Maps concerned with a particular theme or topic of interest, and how things are distributed across space.

2.2 Datums, Coordinate Systems, and Map Projections

Coordinate Systems

Frameworks that are used to define unique positions.

Geographic Coordinate System (GCS)

The coordinate system that is most commonly used to define locations on the three-dimensional earth; it is based on a sphere or spheroid, and uses latitude and longitude to determine location.

Map Projections

A representation of Earth’s surface on a flat plane; The methods and procedures that are used to transform the spherical three-dimensional earth into two-dimensional planar surfaces; Mathematical formulas that are used to translate latitude and longitude on the surface of the earth to x and y coordinates on a plane.

Scale

The ratio between the distance between two locations on a map and the corresponding distance on Earth’s surface.

Spheroid

A spherical shape.

2.3 Representing Geographic Features

Continuous Features

Features that are less well defined and exist across space. The most commonly cited examples of continuous features are temperature and elevation.

Discrete Features

Features that are well defined and are easy to locate, measure, and count, and their edges or boundaries are readily defined. Examples of discrete features in a city include buildings, roads, traffic signals, and parks.

Generalization

The process of resolving conflicts associated with too much detail, too many features, or too much information and data to map.

Image Maps

Maps derived from satellite images and other photos.

Legend

Provides users with information about how geographic information is represented graphically.  Usually consist of a title that describes the map, as well as a clear definition of various symbols, colors, and patterns that are used on the map.

Map Abstraction

The process of moving from the “real world” to the world of maps.

Symbolization

To use representative shapes, icons, or pictures to represent items or spatial phenomena.