Question

Which of the following is/are topological relationship element(s) in GIS?

• A. Adjacency
• B. Connectivity
• C. Containment
• D. Intersection

Hint:

Think about the arc-node GIS data model and which relationships are explicitly stored with every arc and polygon (neighbor, network link, enclosure) versus which relationship is only computed on demand from geometry.

Answer 1

The Correct Option is A, B, C

Step 1: Recall what topology means in GIS.
Topology in a vector GIS is the explicit encoding of the spatial relationships between features that remain true no matter how the map is stretched, rotated or rescaled, as long as the features are not torn apart or reconnected. Classical vector GIS data models build this using three fundamental relationship elements.

Step 2: Explain adjacency.
Adjacency describes whether two polygons share a common boundary, that is, whether they are neighbors. It is stored, for example, by recording which two polygons lie on the left and right side of every boundary arc, so that a query like "find all districts adjacent to this district" can be answered directly from the topological structure rather than by a geometric distance check.

Step 3: Explain connectivity.
Connectivity describes how lines are joined to one another through shared nodes, forming a network. It is stored using the arc-node structure, where every arc records its start node and end node, allowing the system to trace connected paths, for example along a road or river network, which is essential for network analysis such as shortest path routing.

Step 4: Explain containment.
Containment (also called enclosure) describes whether one feature, most often a point or a smaller polygon, lies completely inside another polygon. It underlies operations like point-in-polygon tests and nested administrative boundaries, for example a village polygon contained within a district polygon.

Step 5: Explain why intersection is excluded.
Intersection refers to the geometric overlay of two features to find their common area or crossing points, it is a spatial operation that can be computed directly from the coordinate geometry of any two features, adjacent or not, contained or not, rather than being one of the three basic relationship elements that a topological data structure is built to store and enforce. For this reason, adjacency, connectivity and containment are the standard topological relationship elements, while intersection is treated as a derived overlay operation.

Step 6: Conclusion.
The correct options are adjacency, connectivity and containment.

\[ \boxed{\text{Adjacency, Connectivity, Containment}} \]