हिंदी

Overview of Geographical Information System (GIS)

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Estimated time: 15 minutes
CISCE: Class 12

Key Points: Forms of Geographical Information

  • 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).
CISCE: Class 12

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.
CISCE: Class 12

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.
CISCE: Class 12

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.
CISCE: Class 12

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).
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