Geographical Information System (GIS)


  • “GIS is a computer system capable of assembling, storing, manipulating, and displaying geographically referenced information, i.e. data identified according to their locations.”
  • “A GIS is an organized collection of computer hardware, software, geographic data, and personnel to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information.”



  • Data Capture- Data sources are mainly obtained from manual digitization and scanning of aerial photographs, paper maps, and existing digital data sets.
  • Database Management and Update- Data security, data integrity, and data storage and retrieval, and data maintenance abilities.
  • Geographic Analysis- The collected information is analyzed and interpreted qualitatively and quantitatively.
  • Preparing Result- One of the most exciting aspects of GIS technology is the variety of different ways in which the information can be presented.



  • Data Capture- The input of data into a GIS can be achieved through many different methods of gathering. For example, aerial photography, scanning, digitizing, GPS or global positioning system is just a few of the ways a GIS user could obtain data.
  • Data Storage- Some data is stored such as a map in a drawer, while others, such as digital data, can be as a hardcopy, stored on CD or on your hard drive.
  • Data Manipulation- The digital geographical data can be edited, this allows for many attribute to be added, edited, or deleted to the specification of the project.
  • Query and Analysis- GIS was used widely in decision making process for the new commission districts. We use population data to help establish an equal representation of population to area for each district.
  • Visualization- This represents the ability to display your data, your maps, and information.


Data Types

  1. Vector
  • Points
  • Lines
  • Polygons


  • Advantages of Vector
  • Good Representation of data.
  • Use small file size.
  • Accurate map output.
  • Disadvantages of Vector
  • Complex data structure.
  • Expensive technology.
  • Analysis is complex.


  1. Raster
  • Cell
  • Pixels
  • Elements


  • Advantages of Raster
  • Simple data structure.
  • Cheap technology.
  • Analysis is simple.
  • Same grid cell for several attributes.
  • Disadvantages of Raster
  • Large data volume.
  • Inefficient use of computer storage.
  • Difficult network analysis.
  • Less accurate or attractive maps.
  • Loss of information when using large cells.


Advantages of GIS

  • GIS allows us to view, understand, and visualize data in many ways that reveal relationship, patterns, and trends in the form of maps, globes, reports, and charts.
  • A GIS helps you answer questions and solve problems by looking at your data in a way that is quickly understood and easily shared.
  • GIS give the accurate data.
  • Better predictions and analysis.


Disadvantages of GIS

  • Excessive damage in case of internal fault. Long outage periods as repair of damaged part at site may be difficult.
  • Expensive software.
  • Integration with traditional map is difficult.



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