GIS in Decision Making – Suitability Determination

A geographic information system (GIS), also known as a geospatial information system, is any system for capturing, storing, analyzing, managing and presenting data and associated attributes which are spatially referenced to Earth. In certain countries such as Canada, GIS is more well known as Geomatics. The other definition is, “GIS is a system or tool or computer based methodology to collect, store, manipulate, retrieve and analyse spatially (georeferenced) data”.

In the strictest sense, it is any information system capable of integrating, storing, editing, analyzing, sharing, and displaying geographically referenced information. In a more generic sense, GIS is a tool that allows users to create interactive queries (user created searches), analyze the spatial information, edit data, maps, and present the results of all these operations. Geographic information science is the science underlying the geographic concepts, applications and systems, taught in degree and GIS Certificate programs at many universities.

GIS and geographic information are key components to better decision-making since just about everything a community, business, or public agency does, whether in day-to-day operations or long-term planning, is related to its geography. In fact, many routine operations of business and government are tied to a location and rely on the use of geographic information to accomplish their goal. GIS has been used by the defense, natural resources, and planning communities for many years, and is now being used by many more sectors including transportation, marketing, utilities, emergency management, sales, and education, to name just a few. Examples include:

Land-use planning – Where is growth happening?

Marketing – Where are our customers?

Subdivision review  - Where is the wetland?

Permit tracking – Whose property is the permit attached to?

Parcel/tax mapping – Who are Mr. Farmer’s neighbors?

Natural resource management – Where are the copper deposits/smelters located?

Road and utility maintenance – Where is the downed power line blocking the road?

Crime, fire, accident events & reporting – Where do the most accidents takes place?

Emergency dispatching – Where is the E-9-1-1 call originating from?

For example, administrators involved in municipal planning might want to know how suitable different areas of the town are for development. GIS can be used to generate maps showing where various conditions exist: prime agricultural land, surface water, high flood frequency, and highly erodible land. Planners can use this information to make decisions about zoning designations and building permits.

Geographic information system technology can also be used for scientific investigations, resource management, asset management, environmental impact assessment, urban planning, cartography, criminology, history, sales, marketing, and logistics. For example, GIS might allow emergency planners to easily calculate emergency response times in the event of a natural disaster, GIS might be used to find wetlands that need protection from pollution, or GIS can be used by a company to site a new business location to take advantage of a previously underserved market.

Relating information from different sources

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 milestones.  Any variable that can be located spatially can be fed into a GIS. Several computer databases 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 sensing can be analyzed to produce a map-like layer of digital information about vegetative covers. Likewise, census or hydrologic tabular data can be converted to map-like form, serving as layers of thematic information in a GIS.

Data Modeling

It is difficult to relate wetlands maps to rainfall amounts recorded at different points such as airports, television stations, and high schools. A GIS, however, can be used to depict two- and three-dimensional characteristics of the Earth's surface, subsurface, and atmosphere from information points. For example, a GIS can quickly generate a map with isopleth or contour lines that indicate differing amounts of rainfall.

Such a map can be thought of as a rainfall contour map. Many sophisticated methods can estimate the characteristics of surfaces from a limited number of point measurements. A two-dimensional contour map created from the surface modeling of rainfall point measurements may be overlaid and analyzed with any other map in a GIS covering the same area.

Additionally, from a series of three-dimensional points, or digital elevation model, isopleth lines representing elevation contours can be generated, along with slope analysis, shaded relief, and other elevation products. Watersheds can be easily defined for any given reach, by computing all of the areas contiguous and uphill from any given point of interest. Similarly, an expected path of where surface water would want to travel in intermittent and permanent streams can be computed from elevation data in the GIS.

With the popularization of GIS in decision making, scholars have begun to scrutinize the social implications of GIS. It has been argued that the production, distribution, utilization, and representation of geographic information are largely related with the social context. For example, some scholars are concerned that GIS may turn into a tool of omni-surveillance for dictatorship. Other related topics include discussion on copyright, privacy, and censorship. A more optimistic social approach to GIS adoption is to use it as a tool for public participation.

Notes & Handouts

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