Geographic information system [GIS] is a system of hardware,software, data, people,organizations and industrial arrangements for collecting, storing, analyzing,modeling, displaying, and disseminating information about areas ofthe earth to solve the complex planning and management problems.
Remote Sensing [RS] is the acquisition of data about an object or scene by a sensor that is far from the object. Remote sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area or phenomenon under investigation. Aerial photography, satellite imagery, and radar are all forms of remotely sensed data. Usually, remotely sensed data refer to data of earth collected from sensors on satellites or aircraft.
Many decision makers are increasingly relying on GIS and RS to help them make critical decisions in many disciplines including hiology, hotany, forestry, agriculture, geology, city planning, local government, tourism, mining etc. By putting their spatial data in an integrated system where it can be organized, analyzed, and mapped, they find patterns and relationships that were previously unrecognized.This in turn gives them a deeper understanding of the issues they face, and lets them bring more information and Iess conjecture to the problem solving process.
We live in an age when just about everything that moves or changes over time is being measured. We also live in an age when the computing power and information management tools are in plaoe to allow people to use this data productively. These geo-spatial tools make it possible to focus our attention on large problems, to pinpoint the small ones, and to anticipate those that are waiting in the wings. Natural resource managers are increasingly turning to GIS as the crucible in which this data can be processed and from which solutions can be drawn.
What does it mean of all these improvement in GIS? First, it means that discrete geographic locations on the earth's surface can be stored in computer files as sets of mathematical coordinates. This makes it possible to draw a map on a computer: a map of the world, a map of a country, a map of your neighhorhood.
Second, it means that different map files, or Iayers, of spatial information with common geography can be displayed simultaneously and analyzed with reference to one another. In a map of an agricultural area, one layer might represent the houndaries of the land, another the soil types found there, another the local streams, and still another the changes in eleyation. The analytical power ofa GIS lets you query the system to extract information from multiple Iayers. For example, to find the most suitahle place to plant a crop, you might identify Iocations with a particular soil type, Iying at a certain eleyation, and receiying a specified amount of rainfall.
Third, it means that any guantitatiye information that can be Iinked to geography can be used in a GIS. Not onIy can you represent, for example, the Iocations of toxic waste sites in a giyen region as points on a map, but you can symbolize these points [draw them in different colors, sizes, and shapes] according to any information you have ahout them, such as the type ofwaste they store.
Lastly, it means that geographic features and phenomena can be modeled from sample data. A typical example is that ofa digital terrain model. Sample elevation data is gathered at various points and the GIS uses this input to create a continuous elevation surface, or , in other words, to build a model of the landscape . Similarly, models of processes, such as the spread of oil slicks or wildfires, can be simulated from sample data and from assumptions about the movements of fo rces like winds and tides.