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Geometry Relations

Documentation | Other Specifications | Geometry Relations

TatukGIS supports a powerful, yet easy to manage, mechanism for querying against spatial relationships between two shapes.  This mechanism is known as the Dimensionally Extended 9 Intersection Model (DE-9IM)

The idea is to manage a 9 element mechanism in which each element defines the relationship possibilities between the interiors, exteriors, and boundaries of two shapes.  The relationship is defined in terms of intersection types, or lack of an intersection.

The meanings of interior, exterior, and boundary, as they relate to shape types, are defined as follows:


Interior Boundary Exterior
TGIS_Point Point itself Nothing All except Interior
TGIS_Multipoint Points themselves Nothing All except Interior
TGIS_Arc (lines) Line itself except starting/ending points Starting & ending points of line All except Interior & Boundary
TGIS_Polygon (areas) Area of polygon Outline of polygon All except Interior & Boundary

The nature of the shape intersections is defined by a set of interior, boundary, and exterior relationship possibilities, forming a 3×3 table.

A\B Interior Boundary Exterior
Interior * * *
Boundary * * *
Exterior * * *

The table can be represented by a string (row-by-row) like:

"T*F**FFF*"

Each element of the table represents an intersection possibility:

Type Description
TIntersection exists
FIntersection does not exist      
*Does not matter
0Intersection is a point (dimension = 0)
1Intersection is a line(dimension = 1)  
2Intersection is a polygon (dimension = 2)
2017/02/11 10:27