Package com.vividsolutions.jts.operation.relate
Contains classes to implement the computation of the spatial relationships of Geometry
s.
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:
- Build topology graphs of the two input geometries. For each geometry
all self-intersection nodes are computed and added to the graph.
- Compute nodes for all intersections between edges and nodes of the graphs.
- Compute the labeling for the computed nodes by merging the labels from the input graphs.
- Compute the labeling for isolated components of the graph (see below)
- Compute the
IntersectionMatrix
from the labels on the nodes and edges.
Labeling isolated components
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 1-dimensional, 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 2-dimensional,
a Point-In-Polygon test can be used to determine whether the isolated component is in the
interior or exterior.
Package Specification