Oracle 5.0 Reference Manual page 999

• Its coordinates in its Spatial Reference System, represented as double-precision (8-byte) numbers.
All nonempty geometries include at least one pair of (X,Y) coordinates. Empty geometries contain no
coordinates.
Coordinates are related to the SRID. For example, in different coordinate systems, the distance
between two objects may differ even when objects have the same coordinates, because the distance
on the planar coordinate system and the distance on the geocentric system (coordinates on the
Earth's surface) are different things.
• Its interior, boundary, and exterior.
Every geometry occupies some position in space. The exterior of a geometry is all space not
occupied by the geometry. The interior is the space occupied by the geometry. The boundary is the
interface between the geometry's interior and exterior.
• Its MBR (Minimum Bounding Rectangle), or Envelope. This is the bounding geometry, formed by the
minimum and maximum (X,Y) coordinates:
((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY))
• Whether the value is simple or nonsimple. Geometry values of types (LineString, MultiPoint,
MultiLineString) are either simple or nonsimple. Each type determines its own assertions for
being simple or nonsimple.
• Whether the value is closed or not closed. Geometry values of types (LineString,
MultiString) are either closed or not closed. Each type determines its own assertions for being
closed or not closed.
• Whether the value is empty or nonempty A geometry is empty if it does not have any points.
Exterior, interior, and boundary of an empty geometry are not defined (that is, they are represented
by a
NULL
• Its dimension. A geometry can have a dimension of –1, 0, 1, or 2:
• –1 for an empty geometry.
• 0 for a geometry with no length and no area.
• 1 for a geometry with nonzero length and zero area.
• 2 for a geometry with nonzero area.
objects have a dimension of zero.
Point
objects have a dimension of 2. The dimensions of MultiPoint, MultiLineString, and
MultiPolygon
12.16.2.3. Class
Point
A is a geometry that represents a single location in coordinate space.
Point
Examples
Point
• Imagine a large-scale map of the world with many cities. A
• On a city map, a
Properties
Point
• X-coordinate value.
• Y-coordinate value.
• is defined as a zero-dimensional geometry.
Point
The OpenGIS Geometry Model
value). An empty geometry is defined to be always simple and has an area of 0.
objects are the same as the dimensions of the elements they consist of.
object could represent a bus stop.
Point
objects have a dimension of 1.
LineString
Point
979
Polygon
object could represent each city.