Topological Relationships

Topological relationships are the qualitative relationships of geographic objects that are not affected by continuous distortion, such as translation, rotation, scale, or skew. These relationships are said to exhibit a property known as topological invariant. In other words, topological relationships describe the spatial interrelations among geographic objects, and how they are linked together, without reference to their geographic locations, dimensions, or orientations. Some examples of topological relationships are (a) touch—a point touches a line (e.g., a bridge on a river); (b) cross—a line crosses another line (e.g., a road across a river); and (c) within—a region is completely contained by the boundaries of another region (e.g., an island in a lake). In addition to topological relationships, geographic objects can also have projective relationships, such as ...