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What is GIS?
GIS stands for ‘Geographic Information System’. It is a method for capturing, storing, editing, displaying and analyzing data and associated attributes which are spatially referenced to the earth. Users can utilize this data to create interactive maps for analyzing information and present the results on a map.
GIS data is usually stored in separate databases depending on what category of information is included. In the City of Salem, for example, different datasets exist which allow citizens and City employees to display utilities, zoning districts, parcels and street centerlines, among many others. Each visual representation of this categorized data is called a layer. These layers may be displayed simultaneously, which is useful for analyzing spatial relationships. This process is extremely useful for a host of municipal functions that include planning, wetlands protection, zoning determinations and City service route mapping. As a basic example, the City wetland and parcel layers can be displayed together. A user may then browse for a parcel of interest, allowing investigation
into a number of things, including whether or not a portion of wetland is on a property and how close a wetland is to a home. In this example, the process aids both citizens and planning officials in determining the appropriate permitting process for a construction project.
While all of this talk of layers, data and attributes may sound complicated, users need only to be capable of browsing the internet to reap the benefits of GIS. On the City of Salem Interactive Mapping Website, citizens and Town employees are granted access to various layers, including zoning and historic districts, wetlands, elevation contours, aerial photographs and street names. A basic level of functionality is provided on the site, including tools for measuring distances and areas, selecting parcels, zooming in to
and out from specific locations, querying data for specific attributes and printing maps. Site users can thus perform geographic analyses using the available data.
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