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Geo Information System

  • 5. GIS OBJECTIVES
    1. Maximise the efficiency of planning and decision making
    2. Provide efficient means for data distribution and handling
    3. Elimination of redundant data base - minimise duplication
    4. Capacity to integrate information from many sources
    5. Complex analysis/query involving geographical referenced data to generate new information.

    For any application there are five generic questions a GIS can answer:

    1. Location          - What exists at a particular location?
    2. Condition        - Identify locations where certain conditions exists.
    3. Trends             - What has changed since?
    4. Patterns          - What spatial pattern exists?
    5. Modelling         - What if ……….?
    6. ELEMENTS OF A GIS

    The GIS has been divided into four elements. They are hardware, software, data, liveware. The following table gives complete details of different elements:

    S.No Elements of GIS Details
    1 Hardware Type of Computer Platforms Modest Personnel Computers High performance workstations Minicomputers Mainframe computers Input Devices Scanners Digitisers Tape drivers CD Keyboard Graphic Monitor Output Devices Plotters Printers
    2 Software Input Modules Editing MRP Manipulation/ Analysis Modules Modeling Capability
    3 Data Attribute Data Spatial Data Remote Sensing Data Global Database
    4 Live ware People responsible for digitising, Implementing using GIS Trained

    7. GIS DATA

    Geographical data deals primarily with two types of data: Spatial and Non-spatial. Spatial data is that which has physical dimensions and geographic locations on the surface of earth. Some examples are a river, a state boundary, a lake, a state capital etc. Non-spatial data is that qualifies the data. Attribute or Non-spatial data describes some aspects of spatial data, not specified by its geometry alone.


    8. REPRESENTATION OF SPATIAL INFORMATION

    Point feature - A discrete location depicted by a special symbol or label. A single x, y coordinates
    LINE feature - Represents a linear feature. A set of ordered x, y coordinates
    POLYGON feature - An area feature where boundary encloses a homogeneous area

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    Figure 2. Elements of a Map
    9. REPRESENTATION OF NON-SPATIAL (ATTRIBUTE) INFO

    It consists of textural description on the properties associated with geographical entities. Attributes are stored as a set of numbers and characters in the form of a table. Many attribute data files can be linked together through the use of a common identifier code.

    10. TOPOLOGY

    Geographic data describes objects in terms of location, their attributes and spatial relationship with each other. Topology is a mathematical procedure that determines the spatial relationship of features.

    Some of the advantages of topology are: Polygon network is fully integrated, optimal storage and reduction in redundant information neighbours are identified and polygon in polygon can be represented.