Glossary - Spatial Mathematics: Theory and Practice through Mapping - page 241

Commensurable: Measureable by a common standard.
Conformal: In mapping, where the shape of a small area of the surface
mapped is preserved; preserving local angles.
Conic: In mapping, where the surface of the globe is projected onto the sur-
face of a cone.
Connectivity: A pattern of connection. May have specific meanings in vari-
ous contexts: in graph theory, in topology, in communications, in
brain mapping and other medical contexts, and more.
Contour: An isoline based on elevation data, or height above a fixed refer-
ence point.
Cylindrical: In mapping, where the surface of the globe is projected onto the
surface of a cylinder.
Datum (pl.: datums): Reference from which measurements are made. In
mapping, the datum reference points are based on a mathematically
calculated shape of the Earth.
Decimal degrees: A format of absolute location where the latitude and lon-
gitude values are expressed as decimal fractions.
Degree Confluence Project: An effort to document absolute locations on the
Earth through narratives and photographs using whole-degree inter-
sections of latitude and longitude.
Demographic analysis: Measurement of the dimensions and dynamics of a
population.
Digitizing: In GIS, the process of converting paper map features into a digi-
tal format.
Directional trend: Measures directional influences on data sets.
Dispersion: The spread of a scatter of dots—contrast with clustering.
Dot density map: A thematic map that displays information by showing
numerous dots, each of which represents some specific quantity.
Elevation: The height of a geographic location above a fixed reference point.
Equal area projection: A map of constant area scale. Visual comparisons of
one area to another are true. On an equal area projection Greenland
does not appear larger than Brazil.
Equidistant: A map projection that preserves distance from a standard point
or line.
Four Color Theorem: Four colors suffice to color a map in the plane (with
adjacency defined across edges, not corner points, of polygons).
Fujita scale: A scale for rating the intensity of tornadoes.
Function: A mathematical mapping such that each element of a given set
(domain) is associated with an element of another set (range).
Geocoding: The process of assigning spatial coordinates to geographic fea-
tures in a GIS. Generally, it involves interpolating spatial locations
from street addresses or other spatially referenced data sets.
Geodesic: Loosely, the shortest path on a surface.
Geographic Center: The point on a map that represents the centroid of the
geographical shape defining it. Specifically, it is the point in an area
at the intersection of all straight lines that divide that area into two