18+Times Asked
~90Total Marks
5Topics
HighPriority
1 Geoprocessing Tools
- Buffer: Create polygon at specified distance around feature.
- Clip: Cookie-cutter — extracts features within clip boundary.
- Intersect: Keeps only overlapping area; combines attributes from both layers.
- Union: Combines both layers entirely; splits at boundaries.
- Merge: Combines multiple datasets of same type into one (appends features).
- Dissolve: Merges adjacent features sharing a common attribute value.
- Erase: Removes area of one layer covered by another.
2 Key Comparisons
| Aspect | Clip | Intersect |
|---|---|---|
| Geometry | Input features cut by clip boundary | Overlapping geometry of both layers |
| Attributes | Input layer only | Both layers combined |
| Analogy | Cookie cutter | Overlap finder |
| Aspect | Merge | Dissolve |
|---|---|---|
| Input | Multiple datasets | Single dataset |
| Action | Appends features together | Removes internal boundaries |
| Result | More features | Fewer, larger features |
3 Intersection = Union + Clip
Conceptually: Intersect gives you the overlap area with combined attributes. This is equivalent to first performing Union (combine everything) and then clipping to the overlap zone.
4 Site Selection Workflow
- Define criteria (e.g., within 500 m of road, slope <10°, land use = agriculture).
- Buffer relevant features (roads, rivers, facilities).
- Overlay/intersect all constraint layers.
- Query: select areas satisfying all criteria simultaneously.
- Rank or score remaining candidates.
5 Data Management vs Spatial Analysis
- Data management: Merge, append, dissolve, project, clip (organising data).
- Spatial analysis: Buffer, overlay, intersection, network analysis (answering spatial questions).
Past Exam Questions
+Explain vector geoprocessing tools with diagrams. (Every exam 2071–2082, 6–10 marks)
Buffer, Clip, Intersect, Union, Merge, Dissolve, Erase. Draw before/after diagrams for each. Show attributes in output.
+Compare Clip and Intersect. Compare Merge and Dissolve. (2074, 2076, 2079, 2081)
Clip: geometry from input, attributes from input only. Intersect: overlap geometry, attributes from both. Merge: combines datasets. Dissolve: removes internal boundaries. Use comparison tables.
+Explain site selection using vector overlay analysis. (2073, 2075, 2078, 2080)
Define criteria, buffer, overlay, query, rank. Show a practical example: hospital site selection with road proximity, land use, slope constraints.
+How is Intersection equivalent to Union + Clip? (2074 Magh)
Union combines all features and splits at boundaries. Clipping the union result to the overlap area yields the same as Intersect. Draw Venn diagram.
+Distinguish data management operations from spatial analysis operations. (2072, 2082)
Management: organising data (merge, project, dissolve). Analysis: answering questions (buffer, overlay, proximity). Give 3 examples each.