A GIS is a computerized database management system designed for the capture, storage, analysis and display of spatial (locationally defined) data for the purposes of decision making and research.
Capture and Storage
By gathering data from many different sources (GPS, aerial photographs, scanned maps, conventional surveys, digitized maps, remote sensing [satellite imagery], metes and bounds surveys, etc.) the GIS manager can organize this data and assign different layer names (all trees in one layer, all soil sample sites in one layer, etc.) and classify the data as to its level of accuracy to ground truth (typically referenced to a survey control network).
Analysis and Display
Simple or complex questions can then be "asked" of the data. The program will search all layers pertinent to the characteristics of the query. The final results of this query can be studied and analyzed. Colorful and detailed maps can then be plotted to show a particular condition or set of dynamics.
You would like to install gas heat in your home. You don't know where the gas lines are in relation to your property boundaries. The gas company has told you that they will install the lines free of charge if they are within 50 feet of where the meter can be placed. How do you find out?
You go to the city public works office. They construct a simple query that asks, "are there gas lines within 50 feet of any property boundary of this address?" The computer software takes only a few seconds to find the answer.
GPS then, becomes a vital tool in the collection of GIS data. Not only does GPS define where features are, it can describe these features in intricate detail. This is the intelligence that using a "data dictionary" provides. As the data is exported to a GIS software package, all the spatial definitions (locations) and attribute data are preserved.
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