GIS 101
What is GIS?
Geographic Information Systems are computer systems capable of capturing, storing, analyzing, and displaying geographically referenced information; that is, data identified according to its location. The data is organized into layers of related information and can be combined with other layers of information to perform an analysis. This combination or integration of different layers for the purpose of discovering relationships is the power of GIS as a decision making support tool. For example, by overlaying senior citizen population statistics with existing support service locations a county official is able to identify areas of need within their community.
So how does it work?
GIS technology works by combining the spatial information of features (data referenced to locations on the earth) with the information used to describe those features (commonly referred to as the attribute information). For example, the location of a building would be considered spatial information, while the number of stories in the building would be considered its attribute information. This combination of information allows users to answer both spatial questions (i.e. how many buildings are within a 1 mile radius of a chemical spill) and attribute questions (i.e. how many 10 story buildings have not been inspected for code violations within the last 12 months). The results of these questions are presented visually in the form of a map.
Where does the data come from?
Data is one of, if not the most critical, components of a successful GIS implementation. Data can be created from scratch, obtained from a governmental organization, such as a state of federal agency, or purchased from a commercial vendor. The issue that is driving the need for GIS analysis will dictate the quality and source of the needed data. Remote sensing and global positioning systems (GPS) technologies are common sources of the data in the GIS community.
Remote sensing can be generically defined as the observation of an object, such as earth, from a distance with the intent of gathering information about that object. One of the most popular forms of remote sensing that can be seen almost daily on the nightly news is satellite imagery. While the media relies primarily on satellite imagery to provide a "picture" of a area in discussion (i.e. site of military action), the uses of the technology are much broader, including wildfire risk assesment, agricultural studies, and pollution monitoring just to name a few. At the county level, a common practice is to obtain remote sensing data in the form of aerial photographs. These images are captured from a plane and formatted so that they can be utilized with GIS software to assist in tasks such as planning, emergency management and public safety, property tax assessment, and public works projects.
GPS technology is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS. Counties take advantage of this technology in many ways to capture information about their communities, including asset inventories, environmental condition monitoring, and boundary mapping.
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