GEOS
3.9.0dev

Contains classes to implement the computation of the spatial relationships of Geometry
s.
More...
Classes  
class  EdgeEndBuilder 
Computes the geomgraph::EdgeEnd objects which arise from a noded geomgraph::Edge. More...  
class  EdgeEndBundle 
A collection of geomgraph::EdgeEnd objects which originate at the same point and have the same direction. More...  
class  EdgeEndBundleStar 
An ordered list of EdgeEndBundle objects around a RelateNode. More...  
class  RelateComputer 
Computes the topological relationship between two Geometries. More...  
class  RelateNode 
Represents a node in the topological graph used to compute spatial relationships. More...  
class  RelateNodeFactory 
Used by the geomgraph::NodeMap in a RelateNodeGraph to create RelateNode objects. More...  
class  RelateNodeGraph 
Implements the simple graph of Nodes and geomgraph::EdgeEnd which is all that is required to determine topological relationships between Geometries. More...  
class  RelateOp 
Implements the SFS relate() operation on two geom::Geometry objects. More...  
Contains classes to implement the computation of the spatial relationships of Geometry
s.
The relate
algorithm computes the IntersectionMatrix
describing the relationship of two Geometry
s. The algorithm for computing relate
uses the intersection operations supported by topology graphs. Although the relate
result depends on the resultant graph formed by the computed intersections, there is no need to explicitly compute the entire graph. It is sufficient to compute the local structure of the graph at each intersection node.
The algorithm to compute relate
has the following steps:
IntersectionMatrix
from the labels on the nodes and edges.Isolated components are components (edges or nodes) of an input Geometry
which do not contain any intersections with the other input Geometry
. The topological relationship of these components to the other input Geometry
must be computed in order to determine the complete labeling of the component. This can be done by testing whether the component lies in the interior or exterior of the other Geometry
. If the other Geometry
is 1dimensional, the isolated component must lie in the exterior (since otherwise it would have an intersection with an edge of the Geometry
). If the other Geometry
is 2dimensional, a PointInPolygon test can be used to determine whether the isolated component is in the interior or exterior.