T-GIS Glossary,

This glossary is a sub-set of one developed by the Urban and Regional Information
Systems Association (URISA)

Thematic Map
A thematic map is a representation of an area portraying how one or more real features or theoretical concepts are distributed.

1. Displays a distribution of attributes. Typically a single variable (univariate) map such as soil or land use. Can also depict ranges of calculated values such as: Value category (i.e. 10-20% slope); Density (10-20 persons per acre); Relative suitability scores.
2. Graphic display parameters typically include color assignment, solid fills, hatch patterns, symbols, and other graphic techniques.
3. Uses information stored in a spreadsheet or database to create map displays for graphic presentations.

Tolerance
Tolerance refers to a leeway for variation from a standard. It is also the permissible deviation from a specified value of a structural dimension, often expressed as a percent. Tolerance is a parameter for defining a limiting distance for an operation. For example, a snap tolerance for 2 units apart means that any two endpoints less than 2 units apart will be moved to at a single point location.


Topographic Feature
Spatial representation of the surface features of a place or region on a map, indicating their relative positions and elevations.


Topology
Relationships between spatial features including such things as continuity, nearness, inside vs. outside, etc. Set of defined relationships between links, nodes, and centroids.

1. Polygon Topology - representation of areas and area relationships using links and enclosed areas.
2. Network Topology - representation of a linear network by links and nodes.

Transportation Network
System of interconnecting nodes and links that represent intersections of roadways, railroads, transit lines, or other forms of transportation systems. (See Intersection, Network Routing, Spatial Analysis).