📚 CTEVT | GIS Application – Chapter 2: Spatial Analysis (Full Notes + Practice Questions + Complete PDF )
Spatial Analysis is the heart of GIS Applications (EG 3103 GE).
Once your data is integrated and aligned (Chapter 1), Chapter 2 teaches you how to analyze, interpret, and extract meaningful information from that spatial data.
This chapter is the largest and most important part of GIS Application — covering buffers, overlays, classification, 3D analysis, network routing, and real-world applications used in planning, disasters, surveying, and municipal GIS.
🧩 Chapter Overview: Spatial Analysis
Spatial Analysis = The set of operations that allow GIS users to examine geographic patterns, measure spatial relationships, and make informed decisions.
It helps answer real-world questions like:
✔️ Which buildings lie within 100m of a river?
✔️ Which route is shortest for an ambulance?
✔️ Which areas are flood-prone?
✔️ Where is the best site for a new hospital or school?
Spatial analysis is used in:
- Urban planning
- Transportation planning
- Cadastral mapping
- Disaster and hazard analysis
- Utility and infrastructure mapping
- Land-use suitability analysis
📥 Download the Full Chapter 2 Notes (Free PDF)
🎥 Watch the Chapter 2 Video on YouTube
🎥 Watch the Full Chapter 2 Video
👉 [Click Here to Watch on YouTube]
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🔍 2.1 Introduction: Spatial Analysis
📍 Definition
Spatial analysis refers to the techniques used to analyze geographic data and extract meaningful information based on locations, distances, patterns, and relationships.
GIS is powerful because of these functions — without spatial analysis, GIS would be just a database.
📍 Importance
✔️ Helps solve spatial problems
✔️ Supports evidence-based planning
✔️ Identifies optimal locations
✔️ Measures distances, areas & terrain
✔️ Predicts patterns & future risks
✔️ Useful for decision support systems (DSS)
📍 Types of Spatial Analysis Functions
- Measurement Functions
- Classification Functions
- Overlay Analysis
- Neighborhood/Buffer Analysis
- Network Analysis
- 3D Analysis & Terrain Modeling
⭐ 2.2 Classification and Measurement Functions
🔶 A. Measurement Functions
Used to calculate:
✔️ Distance
✔️ Area
✔️ Length
✔️ Coordinates
✔️ Perimeter
✔️ Distance in Vector Data
Point-to-point Euclidean distance.
✔️ Distance in Raster Data
Based on cell-by-cell connectivity.
✔️ Area Measurement
Used for land parcels, land use types, forests, agricultural fields, etc.
✔️ Length Measurement
Used for rivers, roads, pipelines, electrical lines.
🔶 B. Classification Functions
Classification organizes data into meaningful categories.
Types of Classification:
1️⃣ Manual Classification
User defines classes (e.g., elevation classes: 0–500m, 500–1000m)
2️⃣ Automatic Classification
GIS uses algorithms:
- Natural Breaks (Jenks)
- Equal Interval
- Quantile
- Standard Deviation
Applications:
✔️ Land-use category
✔️ Population density zones
✔️ Soil fertility class
✔️ Slope categories
✔️ Rainfall zones
⭐ 2.3 Overlay Functions and Neighborhood Analysis
🔶 A. Overlay Functions
Overlay = combining layers to produce a new output layer.
Vector Overlay Types
- Union
- Intersect
- Clip
- Erase
- Identity
Raster Overlay Types
- Boolean overlay
- Weighted overlay
- Map algebra
Example:
To find suitable land for agriculture:
- Soil fertility layer
- Slope map
- Water availability
- Land-use map
These layers are overlaid to produce a suitability map.
🔶 B. Neighborhood (Buffer) Analysis
A buffer creates a zone around a feature.
Types:
- Point buffer → e.g., 500m around a school
- Line buffer → e.g., highway influence zone
- Polygon buffer → e.g., protected area boundary
Applications:
✔️ 100m river protection zone
✔️ Noise impact zone around airports
✔️ Safe distance from hazardous areas
✔️ Service coverage area mapping
⭐ 2.4 Network Analysis Function
Network analysis deals with connected linear features like roads, pipelines, rivers.
📍 Basic Terminology
- Node: Junction point
- Edge: Line segment
- Impedance: Cost (time, distance, speed)
- Connectivity: Relationship between nodes
📍 Applications
✔️ Shortest route (ambulance, fire truck)
✔️ Delivery route optimization
✔️ Utility network tracing
✔️ Bus route planning
✔️ Emergency evacuation routes
✔️ Finding nearest facility (hospital, police station)
📍 Example:
Shortest route from office → field location
GIS considers:
- Road length
- One-way restrictions
- Traffic cost
- Connectivity
and gives the optimal route.
⭐ 2.5 3D Analysis
3D analysis helps understand terrain shape, slope, aspect, height, and volume.
GIS uses elevation datasets such as:
- DEM (Digital Elevation Model)
- DSM (Digital Surface Model)
- DTM (Digital Terrain Model)
- TIN (Triangulated Irregular Network)
🔶 A. 3D Surface Representation
GIS converts elevation points into:
✔️ Contours
✔️ DEM
✔️ TIN
✔️ Surface models
🔶 B. Terrain Derivatives
✔️ Slope
Steepness of ground surface.
✔️ Aspect
Direction of slope (N, NE, S, etc.)
✔️ Hillshade
Shaded relief model showing terrain illumination.
🔶 C. Contour and Profile Generation
GIS can generate:
✔️ Contours from DEM
✔️ Cross-section profiles
✔️ Elevation gradients
Useful for:
- Road design
- Irrigation channels
- River alignment
- Geological surveys
🔶 D. Surface Area & Volume Calculation
Used for engineering projects:
✔️ Earthwork calculation
✔️ Road cut & fill
✔️ Reservoir volume estimation
✔️ Quarry depth & volume
🔶 E. Applications of DEM in Planning
✔️ Hydrology & watershed analysis
✔️ Flood risk mapping
✔️ Hazard & landslide mapping
✔️ Land-use suitability
✔️ Urban expansion monitoring
✔️ Road alignment and planning
🧪 Practical Example (QGIS/ArcGIS)
📌 Case: Finding Safe Zones from Flood-Prone Rivers
Input Layers:
- River shapefile
- DEM
- Settlement points
- Road network
Steps:
1️⃣ Buffer river 100m
2️⃣ Overlay buffer with settlements
3️⃣ Extract high-elevation zones from DEM
4️⃣ Use network analysis to find safe evacuation routes
Final output → Flood Safe Zones Map
📝 Short Questions
- Define spatial analysis.
- What is buffer analysis?
- List any three vector overlay operations.
- What is network analysis?
- Define a node and edge.
- What is DEM?
- Differentiate between slope and aspect.
- What is classification?
- What is a suitability map?
- What is a raster overlay?
- What is hillshade?
- What is Euclidean distance?
📝 Long / Analytical Questions
- Explain spatial analysis and its importance in GIS.
- Describe measurement and classification functions with examples.
- Explain vector and raster overlay operations in detail.
- What is buffer analysis? Discuss its types and applications.
- Explain network analysis with real-world examples.
- Describe DEM, DSM, and TIN.
- How are slope, aspect, and hillshade generated from DEM?
- Discuss surface area and volume computation in GIS.
- Explain the steps involved in 3D surface modeling.
- Write a real-world case study where spatial analysis solved a planning problem.
🎯 Key Takeaways
✔️ Spatial analysis is the core functional strength of GIS.
✔️ Overlay, buffer, classification, network routing, and 3D analysis form the backbone of GIS Applications.
✔️ DEM and 3D tools help in engineering planning, hazards, and environmental analysis.
✔️ Network analysis is crucial for route optimization and service delivery.
✔️ GIS makes real-world decision making more accurate and scientific.
📂 Download Free PDF Notes – Chapter 2: Spatial Analysis
🔽 [Download Notes – Chapter 2 (PDF)]
🎥 Watch the Full Chapter 2 Video
👉 [Click Here to Watch on YouTube]
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