📚 GIS Basics – Chapter 2: GIS and Spatial Data Models
(CTEVT Diploma in Geomatics Engineering – 3rd Semester Notes + Free PDF + Video)
🌍 Geographic Information System (GIS) is more than just digital mapping — it is a powerful system that integrates hardware, software, people, data, and methods to analyze and visualize spatial information.
Chapter 2 of GIS Basics (EG 2105 GE) introduces the heart of GIS: Spatial Data Models — the way real-world geographic features are represented digitally.
📥 Download Chapter 2 PDF Notes (Free)
🎥 Watch the Full Chapter Video on YouTube
🎥 Watch the Full Chapter 2 Video
👉 [Click Here to Watch on YouTube]
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📌 Overview
Geographic features like rivers, roads, forests, and buildings exist in the real world with location and shape. To analyze them using a computer, they must be converted into digital models.
✨ Spatial Data Models define:
- How geographic objects are stored
- How spatial relationships are maintained
- How GIS performs analysis
This chapter explains Vector, Raster, and TIN models — the foundation of all GIS operations.
🛰️ What is GIS? (Quick Recap)
A Geographic Information System (GIS) is:
“A computer-based tool for capturing, storing, managing, analyzing, and displaying spatial data.”
GIS works with two types of information:
- Spatial Data: Location, shape, geometry (point, line, polygon)
- Attribute Data: Descriptions (name, population, type, length, etc.)
GIS combines both to make intelligent maps.
🧩 Components of GIS
GIS consists of five major components:
1️⃣ Hardware – Computers, GPS, scanners
2️⃣ Software – QGIS, ArcGIS, ERDAS
3️⃣ People – GIS operators, analysts, cartographers
4️⃣ Data – Spatial + non-spatial datasets
5️⃣ Methods – Procedures and workflows
🔍 Types of GIS Users
GIS is used by:
- Surveyors
- Engineers
- Planners
- Environmentalists
- Disaster managers
- Students & researchers
🗂️ Spatial Data Models (Main Topic of Chapter 2)
This chapter covers three major data models:
🎯 1️⃣ Vector Data Model
Vector data is used to represent discrete, clearly defined features.
🔹 Geometry Types
- Point: Schools, wells, utility poles
- Line: Rivers, roads, boundaries
- Polygon: Parcels, lakes, land use zones
🔹 Vector File Formats
- Shapefile (.shp)
- GeoJSON
- KML
- GPKG
🔹 Advantages
✔ High positional accuracy
✔ Good for map editing
✔ Ideal for network analysis (roads, utilities)
🔹 Disadvantages
✘ Cannot represent continuous surfaces well (rainfall, temperature)
✘ Complex topology rules required
🌈 2️⃣ Raster Data Model
Raster represents the world as a grid of cells (pixels).
🔹 Examples
- Satellite images
- DEM (Digital Elevation Model)
- Land cover maps
- Heat/surface models
🔹 Resolution
Smaller cell size = higher resolution.
🔹 Advantages
✔ Best for continuous data
✔ Great for spatial modelling
✔ Fast processing for large datasets
🔹 Disadvantages
✘ Large file size
✘ Less precise for boundaries
✘ Requires resampling for accuracy
🏔️ 3️⃣ TIN (Triangulated Irregular Network)
TIN represents terrain using interconnected triangles.
🔹 Uses
- 3D terrain modelling
- Volume calculation
- Slope & aspect analysis
- Hydrology studies
🔹 Advantages
✔ Highly accurate for elevation
✔ Efficient for uneven terrain
🔹 Disadvantages
✘ Complex structure
✘ Not suitable for large continuous surfaces
🌍 Applications of Data Models
| Data Model | Best For |
|---|---|
| Vector | Parcels, roads, utilities, boundaries |
| Raster | Satellite images, DEM, land cover |
| TIN | Terrain analysis, 3D modeling |
🇳🇵 Nepalese Examples
📌 Survey Department – Topographic Maps
- Vector for roads, buildings, boundaries
- Raster for aerial photos and DEM
- TIN for terrain modeling (especially in hilly regions)
📌 Local Level Planning
Municipalities use:
- Vector parcels
- Raster base maps
- TIN for hillslope analysis
🧪 Practical Exercises (As Per Syllabus)
1️⃣ Identify vector and raster layers in QGIS
2️⃣ Import and view shapefile and raster data
3️⃣ Calculate area and length using attribute table
4️⃣ Visualize DEM as hillshade, slope, aspect
5️⃣ Compare vector vs. raster representations of same area
6️⃣ Build a simple TIN from elevation points
🧠 Key Takeaways
✔ GIS works with spatial + attribute data
✔ Vector = Discrete objects
✔ Raster = Continuous surfaces
✔ TIN = 3D terrain modeling
✔ Each model has unique strengths and applications
📝 Short Questions
- What is GIS?
- Define spatial and attribute data.
- List three examples of vector features.
- What is raster resolution?
- What are the advantages of the vector data model?
- Define TIN.
- Mention any two GIS applications.
📚 Long / Analytical Questions
- Explain the vector data model with examples and advantages.
- Describe the raster data model, its structure, and applications.
- Compare vector, raster, and TIN models.
- Explain the components of GIS.
- What is GIS workflow? Describe each stage.
- Discuss the importance of spatial and attribute data in GIS.
📂 Download Free PDF Notes – Chapter 2: GIS & Spatial Data Models
🔽 [Download Notes – Chapter 2 (PDF)]
(PDF will include neatly formatted diagrams, tables, and examples)
🎥 Watch the Full Chapter 2 Video
👉 [Click Here to Watch on YouTube]
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