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Geometric Planar Properties of Basic MapInfo Objects as Used Within spatialSQL

spatialSQL  refers to properties of objects such as end, edge, node. This table lists these properties. Whilst the edge of a point object is meaningless, this definition indicates whether the attribute exists for the purposes of the described spatial operation. 

Underline indicates MapInfo defined or used property.

Object

Object Type

Property

Symbol

Line

Polyline

Polygon

Object
Components

Node

Intrinsic

End

Properties

Edge

Boundary

Interior

 

 

 

Rotation

 

 

 

MBR

 

Direction

 

Geometric
Centroid

Derived

Shifted
MBR
Centroid

Properties

Visual Centroid

 

 

 

Principal
Axes

Side

All

 

Aspect

All

 

Applied
Properties

Style

symbol
style

line
style

line
style

region
style

  

  1. For a polyline aspect and side are determined at the segment containing the centroid.
  2. Node means any node defined for an object.
  3. For a polygon, end is any single node on the boundary. Whilst a polygon has a defined start node, its definition is arbitrary, likely to change with basic manipulation and thus of dubious value.
  4. An edge match includes the nodes defining that edge.
  5. The centroid of a region may be outside the region boundary. (eg. U-shape)
  6. A point object has all sides and aspects.
  7. A region object has no sides or aspect definition.
  8. The end segments of linear objects may be considered as extending to the limit of data bounds for the purposes of side and aspect. The actual extent is usually determined by a buffering method.
  9. Style attributes are only mentioned here because they can change the apparent (visual) properties of objects. (eg. hide the boundary of a polygon).
  10. Object collection properties are a superset of object properties. eg. A multi-section polyline will contain multiple pairs of ends. A region is a collection of polygons.
  11. Principal Axes:
    Ixx is the moment of inertia (2nd moment of area) about the x-axis
    Iyy is the moment about Y
    Ixy is the product of inertia
    I1,I2 are principal moments of inertia.
    Theta is the angle of the principal axes to the X axis.

 

 

Spatial Relationships

The SQL method compares object pairs in the following manner:

Spatial Operator

Description

As
defined
by

Intersects

The boundary or interior of the objects intersect

MapInfo

Within

The centroid of the first object is within the boundary of the second object

MapInfo

Entirely within The boundary of the first object is entirely within the boundary of the second object.

MapInfo

Contains

The boundary of the first object contains the centroid of the second object

MapInfo

Contains entire

The boundary of the first object contains the boundary of the second object

MapInfo

Touch

A node on one object intersects the boundary of the second object

spatialSQL

Touch Ends One or both ends of the objects touch. Regions touch at a single node

spatialSQL

Touch Edge One or more edges of the objects touch along the full length of one edge.

spatialSQL

Disjoint

Boundary and interior of the objects dont intersect

spatialSQL

Equals Scalar The boundary of the objects have identical geometry but in either node order.

spatialSQL

Equals

The boundary of the objects have identical geometry and the direction of the objects are identical.

spatialSQL

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Last modified: Mar24, 2008