Arc
A topological entity that starts and ends at a node. Although it is
often graphically depicted as a line, an arc only denotes a
topological link between two nodes, and the geometrical shape of the
link is not important. It is also called a link, an edge,
or a 1-cell.
Attributes
Characteristics of geographic features. Examples are area, length,
owner name, and address.
Attributes, Non-Spatial
Attributes that are not related to the geometry of features.
Examples are population of a country and name of a highway.
Attributes, Spatial
Attributes that are directly or indirectly related to the geometry
of features. Examples are length of a road and area of a country.
Attributes, System-Defined o
Those attributes which are managed directly by CARIS.
Attributes, User-Defined o
Those attributes which are not managed directly by CARIS but are
stored separately in a relational database.
B
Bounding Rectangle
The smallest upright rectangle enclosing a feature, and it is also
called a minimum bounding rectangle. It can be defined by two
diagonal points, one from the smallest x and y coordinates, and the
other from the largest x and y coordinates of the feature. The main
use of this rectangle is to approximate the shape of feature so as to
reduce the time it takes to retrieve features.
Buffer Zone
A modeled region around a feature. It is usually described as a
polygon with its boundary at a constant distance from the given
feature. A buffer zone around a point is a circle.
C
Co-locating lines
Lines that share the same space. For example, a river and an
international boundary co-locates if they share the same line.
Control Points
They are points which can be used to relate and then transform
geometric objects from one configuration to another. If the two
configurations are in different coordinate systems, control points are
used to transform the objects from one system (such as a digitizer
coordinate system) to another (such as a ground coordinate system). If
the two configurations are in the same coordinate system, control
points are used to transform from a distorted configuration to a more
accurate one.
Coordinate, Absolute
Coordinate with its value measured from a single origin in the
coordinate system. See also Coordinate, Relative.
Coordinate, Relative
Coordinate with its value measured from a nearby point instead of
from the single origin in the coordinate system. The purpose is to
reduce its magnitude so as to save storage space. See also Coordinate,
Absolute.
Coordinate System
It is a means of specifying unique position for geographic
features. In a two-dimensional coordinate system, two coordinates are
used to specify position on a plane. In a three-dimensional coordinate
system, an additional third coordinate is used to specify elevation or
depth.
Coordinate System, Geographic
A coordinate system defined over a mathematical body, usually an
ellipsoid, approximating the earth. The coordinates are in degrees of
latitude and longitude.
Coordinate System, Ground
A coordinate system defined over a flat map. The coordinates are
usually in metres along the Northerly and Easterly directions.
Coordinate System, Scaled Ground o
A coordinate system which is a scaled version of the ground system.
The constant scale factor applied to the coordinates helps to change
them from decimal numbers to integers, thus reducing computer storage.
Corridor
Same as Buffer Zone.