- Types of Geographical Data: Two types – Spatial data and Non-spatial (attribute) data.
- Spatial Data: Shows location and shape (point, line, area) on a map; used in GIS.
- Non-spatial Data: Gives description or information about spatial data (e.g., literacy rate).
- GIS Features: Uses digital data, symbols, colours and coordinate system to show exact location.
- Advantages of GIS: Allows easy analysis, data linking, map updating and spatial operations (like overlay and buffering).
Key Points
Key Points: Components of GIS
- Main Components of GIS: Hardware, Software, Data and People.
- Hardware: Includes computers, storage devices, display systems and input-output devices.
- Software: Used to store, manage, analyse, transform and display geographical data.
- Data: Includes spatial data (location, shape) and non-spatial data (attributes).
- People: Skilled users are needed to operate GIS, analyse data and make decisions.
Key Points: Spatial Data Formats
- Two Spatial Data Formats: Raster format and Vector format.
- Raster Format: Data shown as grid cells (rows and columns); each cell has a value (pixel).
- Uses of Raster: Suitable for satellite images, aerial photos and background maps.
- Vector Format: Uses points, lines and polygons based on coordinates (X, Y, Z).
- Uses of Vector: Suitable for precise features like roads, boundaries and cultural features.
- Raster – Pros & Cons: Simple and good for continuous data, but may lose small details and needs more memory.
- Vector – Pros & Cons: More accurate and needs less memory, but complex and costly to manage.
Key Points: Spatial and Attribute Data Likages
- Data Linkages in GIS: Spatial and attribute data are linked to combine and compare different data sets.
- Exact Matching: Data are joined using a common key (e.g., same town name in two files).
- Hierarchical Matching: Small area data are grouped to match larger area data before linking.
- Fuzzy Matching: Used when boundaries of two data sets do not exactly match.
- Spatial Analysis: GIS analyses spatial and non-spatial data to solve real-world problems.
- Overlay Operation: Two or more map layers are combined to create a new map layer.
- Buffer Operation: A zone is created around a point, line or area to study services or effects (e.g., pollution, facilities).
Key Points: Forms of Geographical Information
Key Points: Sequence of GIS Activities
- Sequence of GIS Activities: Spatial data input → Attribute data entry → Verification & editing → Linking data → Spatial analysis.
- Sources of Spatial Data: Can be obtained from digital data suppliers or created by manual input.
- Data Compatibility: Scale, geo-referencing system, data quality and method must match before using in GIS.
- Manual Data Input Methods: Digitisers, scanners and stereo plotters are used to enter spatial data.
- Entering Attribute Data: Attribute data describe features (e.g., river width, flow) and are stored in databases.
- Data Verification & Editing: Data must be checked for errors like wrong scale, distortion or incomplete data.
- Linking & Analysis: Spatial and attribute data are linked together for further spatial analysis in GIS.
