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Geographic information systems technology can be used for scientific investigation s, resource management and development planning . For example, a GIS might allow emergency planners to easily calculate emergency response times in the event of a natural disaster, or a GIS might be used to find wetlands that need protection from pollution.
If you could relate information about the rainfall of your state to aerial photographs of your county, you might be able to tell which wetlands dry up at certain times of the year. A GIS, which can use information from many different sources in many different forms, can help with such analyses. The primary requirement for the source data consists of knowing the locations for the variables. Location may be annotated by x,y, and z coordinates of longitude, latitude, and elevation, or by other geocode systems like ZIP codes or by highway mile markers. Any variable that can be located spatially can be fed into a GIS. Several computer databaseA database is an information set with a regular structure. Any set of information may be called a database. Nevertheless, the term was invented to refer to computerised data, and is used almost exclusively in computing. Sometimes it is used to refer to nos that can be directly entered into a GIS are being produced by government agencies and non-government organizations. Different kinds of data in map form can be entered into a GIS.
A GIS can also convert existing digital information, which may not yet be in map form, into forms it can recognize and use. For example, digital satellite images generated through remote sensingIn the broadest sense, remote sensing is the measurement or acquisition of information of an object or phenomenon, by a recording device that is not in physical or intimate contact with the object. It is the utilization at a distance (as from aircraft, sp can be analyzed to produce a map-like layerA layer is the following: In abstraction, a layer is an abstract place conceived as having depth. In telecommunications a layer is an F region. In telecommunications networks and open systems architecture a layer is a group of related functions that are p of digital information about vegetative covers.
Likewise, censusA census is the process of obtaining information about every member of a population (not necessarily a human population). It can be contrasted with sampling in which information is only obtained from a subset of a population. As such it is a method used f or hydrologic tabular data can be converted to map-like form, serving as layers of thematic information in a GIS.
How can a GIS use the information in a map? If the data to be used are not already in digital form, that is, in a form the computer can recognize, various techniques can capture the information. Maps can be digitized, or hand-traced with a digitizerIn telecommunication and computing, the term digitizer has the following meanings: 1. A device that converts an analog signal into a digital representation of the analog signal. Note: A digitizer usually samples the analog signal at a constant sampling ra, to collect the coordinates of features.
Electronic scanning devices will also convert map lines and points to digits.
A GIS can be used to emphasize the spatial relationships among the objects being mapped. While a computer-aided mapping system may represent a road simply as a line, a GIS may also recognize such a road as the border between wetland and urban development, or as the link between Main Street and Blueberry Lane.
Data capture - putting the information into the system - consumes much of the time of GIS practitioners. Identities of the objects on the map must be specified, as well as their spatial relationships. Editing of automatically captured information can also prove difficult. Electronic scanners record blemishes on a map just as faithfully as they record the map features. For example, a fleck of dirt might connect two lines that should not be connected. Extraneous data must be edited, or removed from the digital data file.
A GIS makes it possible to link, or integrate, information that is difficult to associate through any other means. Thus, a GIS can use combinations of mapped variables to build and analyze new variables.
Using GIS technology and water-supplier billing information, it is possible to simulate the discharge of materials in the septic systems in a neighborhood upstream from a wetland. The bills show how much water is used at each address. The amount of water a customer uses will roughly predict the amount of material that will be discharged into the septic systems, so that areas of heavy septic discharge can be located using a GIS.
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