About

• “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.”

Principle

• 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.

Functions

• 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.

2. 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.