Spatial query is a query method that selects map features based on their spatial relationships to other feature. Currently, 8 spatial query operators are supported. They are: Cross, Contain, Within, Overlap, Disjoint, Touch, Identity, Intersect.
The 3 features involved are: the searching object, the searched layer, and the result recordset. The illustration for each operator depicts the searching object and the result dataset. The searching object is in green, the searched layer is in black, and the result recordset is in red.
Cross
Return line or region objects in the searched layer (line, region. CAD) crossed by the searching object (line).
- Relationship: The searching object (A) crosses the searched object (B).
- Search line with line: The line traverses another line, coming in from one side and going out from the other side. The intersection should be points. The intersection of the interior of A and the interior of B cannot be null and the topological dimension is 0.
- Search region with line: The line traverses the Region, with at least one of the two endpoints of the line being outside of the Region.
Cross Operators:
Contain
Return objects (point, line, region, text, CAD) in the searched layer contained by the searching object (point, line, region). It is not necessary to be fully contained. It is OK to have boundary intersection.
- Relationship: Searching object A contains searched object B (boundary intersection of A and B can be not 0).
- The intersection of the exterior of A and the interior of B is null and the intersection of the interior of A and the interior of B is not null, or the boundary of A and the interior of B have no intersection.
- Dimensions of A >= Dimensions of B
Contain Operators:
Within
Return objects in the searched layer (point, line, region, CAD) that contain the searching object (point, line, region). Returned regions must fully contain (including boundary touch) the searching object; returned lines must fully contain the searching object; returned points must be identical to the searching object.
- Relationship: The searched layer B contains the searching object A. It is the opposite of Contain.
Within Operators
Overlap
Return objects in the searched layer (line, region, CAD) that are partly overlapped with the searching object (line, region).
- Relationship: The searching object (A) overlaps with the searched object (B).
- Dimension of A is identical to the dimension of B.
- The intersection (C) of the interior of A and the interior of B is not null, the exterior of A and the interior of B cross, and the exterior of B and the interior of A cross.
- The type of C is identical to that of A.
Overlay Operators
Disjoint
Return objects in the searched layer (point, line, region, CAD) disjoint with the searching object (point, line, region).
- Relationship: The searching object (A) is disjoint with the searched object (B).
Disjoint Operators
Touch Operators
Identity
Return objects in the searched layer (point, line, region, CAD) that are fully overlapped with the searching object (point, line, region). The object type and coordinates must be the same.
- Relationship: The type of the searching object A and the type of the searched object B must be the same, the intersection of the interior of A and the interior of B is not null, the intersection of the boundary of A and the exterior of B is null, the interior of A and the exterior of B is null, and the vertices can be not identical.
Identity Operators
Intersect
Return objects (point, line, region, Text, CAD) in the searched layer that are intersected with the searching object (point, line, region).
- Relationship: The searching object (A) intersects with the searched object (B).
Intersect Operators
