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TIGER/Line(R) Files, 1994
Appendix B
SDTS Definitions for Spatial
Objects
The spatial objects in TIGER/Line belong to the "Geometry and
Topology" (GT) class of objects in SDTS. The definitions are from
FIPS Publication 173, SPATIAL DATA TRANSFER STANDARD (SDTS)
(August 28, 1992) Section 2-2, Classification and Intended Use of
Objects, pp. 11-20.
* Node: "A zero-dimensional object that is a topological
junction of two or more links or chains, or an end point of a link
or chain," is a node.
* Entity point: "A point used for identifying the location of
point features (or areal features collapsed to a point), such as
towers, buoys, buildings, places, etc."
* Complete chain: "A chain [a sequence of non-intersecting
line segments] that explicitly references left and right polygons
and start and end nodes." The shape points combine with the nodes
to form the segments that make a complete chain.
* Network chains: "A chain that explicitly references start
and end nodes and not left and right polygons."
* GT-polygon: "An area that is an atomic two-dimensional
component of a two-dimensional manifold, [which is defined as] one
and only one planar graph and its two-dimensional objects." GT-
polygons are elementary polygons that are mutually exclusive and
completely exhaust the surface.