An example in geographic information systems

• Objects
  • polygonal objects: states, counties, cities, plots of land
  • linear objects: roads, rivers, canals
  • point objects: university in a city map, cities in a country map
    soil pits, drilling holes
  • Relational representation:
    • POINTS (Point_id, x-coordinate, y-coordinate)
    • LINES (Line_id, x_o, y_o, x_d, y_d)
      • x_o: x-coordinate of origin
      • x_d: x-coordinate of destination
    • POLYGONS (Polygon_id, Line_1, Line_2, ...)

• operations
  • map display
    • construct from stored information
    • store map image as a binary large object (BLOB)
  • intersection operation
    • Find all roads going through Baltimore city
    • Find all roads intersecting I-95
  • overlay map layers: road network, land use (wetland, city park, agricultural zones)

• Indexing methods using spatial information

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