Glossary - Spatial Mathematics: Theory and Practice through Mapping - page 245

mapped features exhibit a directional trend and the amount of scatter
of those features.
State Plane Coordinate System: A set of 124 geographic zones or coordinate
systems created to refer to ground positions in the United States of
America.
Stereographic projection: A perspective projection of the globe from a point
on the surface to a plane tangent at the point antipodal to the selected
surface point of projection.
Street addressing: A method of assigning a numerical designation to prop-
erties with regards to their position in the transportation network;
may vary regionally and from country to country.
Symbology: A system of (map) symbols, including size, color, shape, and
other attributes.
Tessellation: A pattern of shapes that fit together with no gaps; a tiled floor
is a physical model.
Thiessen polygon: Individual area of influence around each point in a
distribution.
TIGERweb: Interactive online map of US Census data.
Tissot Indicatrix: In mapping, the use of small ellipses to measure projec-
tion distortion.
Topographic map: A map that indicates, through a series of contour lines or
hill shadings, the relief or physical characteristics of a landscape. A
topographic map also typically shows other physical features such as
rivers and human-constructed objects such as buildings and roadways.
Topology: A branch of mathematics concerned with properties that are pre-
served under continuous transformations.
Tracts or Census tracts: A geographic region defined for the purpose of the
taking of a census. It is composed of a group of block groups, typi-
cally containing a few thousand residents. Census tracts nest within
county equivalents.
Transformation: A mathematical mapping from one set to another (or itself).
UTM: Universal Transverse Mercator—A grid-based method of designating
absolute locations on the surface of the Earth.
Vector format: A format for storing spatial data as points, lines, or areas
(polygons).
Voxel: A voxel is a 3D (volume) pixel.
Web GIS: Geographic Information Systems tools, maps, and data served on
the Internet; also sometimes referred to as web mapping.
Web Mercator Auxiliary Sphere: A tiling scheme to produce sphere-based
geographic coordinate system.
Weighted mean center: In a GIS, the point considered to be the center of a
distribution of points with weight added in relation to some attribute,
such as population, pH, or noise level.