Scenario #1: You’ve been working hard to pull together statistical information to provide an economic profile of your community to potential businesses. You’ve collected a variety of data on the local labor force and the quality of services and amenities in the area. You would also like to include information about where your community is located relative to major regional markets within Ohio and the midwest, such as Cleveland and Chicago. GIS Solution: A regional map with your community highlighted in the center illustrates the major highway transportation routes that connect your community with regional markets. Distance bands drawn around your community illustrate its proximity to the major urban centers and markets. Click here to see an example for Washington County, Ohio. Scenario #2: You are working with a group of business and civic leaders to revitalize retail development in your local downtown business district. You have data on the properties that are currently vacant, including their street address, square footage, and building owner. You've talked to a prospective client over the phone who wants to know what other businesses are in the same block of a vacant property and what you think the potential demand for a bookstore would be based on the surrounding residential population. GIS Solution: A geographic database of all the properties within the downtown business district tracks both the location and the data that you have for each property. A query of this database based on the location of all businesses identifies the other businesses located in the same block. A map and accompanying table illustrate this information. You also have population, income, and retail sales information for your region. You select the population living within a 10 mile radius of the business district and calculate the potential sales for bookstores within this area based on your demographic data. A map illustrates the areas with the highest potential. Click here to see an example of a regional analysis of total retail sales for Champaign County, Ohio. So what exactly is GIS?GIS, which stands for Geographic Information System, is a software database program that runs on personal computers. The key feature of GIS is that it links data to geographic locations. For example, GIS can link information -- such as the population, median household income, and number of businesses within counties -- with the geometric shape and geographic location of the counties. The difference between a GIS and a computer database program such as Excel or Lotus 1-2-3 is that a GIS can be used to represent and analyze data from a spatial perspective. For example, using a GIS you can easily answer questions such as: What counties border County Z? How far is City A from Cities B,C, and D? Which businesses are located between Streets X and Y? Answering these questions with an aspatial database program is not possible. GIS also provides a means to link data from different sources by using the spatial location as the common link. For example, a GIS can be used to combine data by census tract with data by school districts. Questions that a GIS Can Answer Location: What is at...? A GIS can be used to display the features that exist at a certain location or that are associated with a certain location. For example, a GIS can be used to map public infrastructure, such as roads, utility lines, and schools. It can also be used to display characteristics that are associated with a particular place, for example, the population or median household income of counties within a state. Click here to see the location of highways and population centers for the state of Ohio. Trends: What has changed...? By comparing data from two or more time periods, a GIS can be used to identify trends over time. For example, by looking at population change between two points in time, high growth areas within a region can be visually identified. Click here for an Ohio example. Condition: Where is the location that meets these criteria...? A GIS can be used to identify locations that meet certain criteria. This is often necessary for siting a public or private facility that may require a minimum area and proximity to certain services, such as transportation routes. Suppose you need to identify potential sites for an industrial park within your county. The park may have certain criteria -- for example, it needs to be located within close proximity of a major highway access point, might have a minimum lot size, and cannot be located within a floodplain. Using the query and selection tools that are available with a GIS, you can perform a series of queries on land parcel data that would identify those parcels that meet the criteria. The results of your query can be easily displayed with a map. Pattern: What is the spatial pattern...? A GIS makes it possible to view and analyze spatial patterns exhibited by the data. By visualizing the geographical distribution of the data, spatial trends and patterns that otherwise could not be detected can be highlighted. For example, click here to see a map of Clark County that illustrates the spatial pattern of retail establishments relative to population density within the county. By displaying this information spatially, the location of retail clusters within and outside Springfield are revealed -- something that could not be detected if the data were displayed in a table or spreadsheet. Patterns based on distance measures can also be examined using a GIS. For example, suppose you want to know the pattern of urban and rural towns based on their relative distance to the nearest metropolitan area. By using a distance calculation command, this question is easily answered and the resulting pattern displayed with a map. Click here to see the pattern of urban and rural towns in Ohio as defined by their distance from the nearest MSA. Modeling: What if...? GIS can be used to generate "what if" scenarios based on statistical analysis from an underlying model. For example, using the estimates from a regression model of student math scores, predictions can be made regarding how the math scores might change under different school policy scenarios. Other examples of "what if" scenarios include predicting how land use patterns might change in response to different policies, e.g. a road widening, sewer line extension, or change in zoning. Applying GIS to Economic Development GIS is a tool that can be used in a variety of ways to enhance economic development efforts. Thematic maps that illustrate spatial patterns of population, income, existing businesses by sector, or infrastructure are straightforward to create using a GIS. In addition, a number of spatial analyses can be performed that inform economic development strategies. Examples include: Retail trade area analysis: Secondary data, such as the location of customers and businesses, as well as primary data from business and consumer surveys can be used in a GIS to identify retail trade areas. Trade areas demarcate the extent of the local market for a particular good or service. Potential demand for a good or service can be calculated within a trade area, taking into consideration the spatial distribution of income and other household demographic data. Site suitability and selection: Potential locations for an industrial facility or commercial business can be identified based on location criteria, such as proximity to transportation routes, public services, suppliers, and customers. In addition, a GIS can be used to predict how the location of a new business at a particular location might impact demand for goods and services provided by existing businesses. Land use planning: A GIS can be used to analyze the location of current and future residents relative to current and planned infrastructure (e.g., schools, roads, and sewer) to evaluate current and potential demand for public services. Land value assessment: The location, use, and assessed value of land parcels can be stored and analyzed using a GIS. A GIS can be used to estimate the value of a land parcel in its current or an alternative use based on its location, parcel characteristics, and zoning. Identifying new markets: A GIS can be used to map an existing customer database and to identify areas that have the highest potential for new customers. Making maps for marketing: Formerly the job of cartographers, high quality maps can now be produced by anyone willing to learn GIS. Maps can be printed directly or imported into a publication document or computer presentation file. Some Basic GIS Terminology*Attribute data is any piece of information that describes a geographic feature. For example, the attributes of a county may include its name, size, population, median income, and a variety of other economic and demographic variables. Buffer is a zone around a geographic feature that can be calculated in terms of distance or time. For example, a buffer around a store can be calculated in terms of miles from the store or in terms of the length that a car can travel from the store within 15 minutes. Click here for an example of distance buffers. Census block group is the second smallest geographical unit that the U.S. Census Bureau uses to collect and tabulate the census data. Census block groups are made up of census blocks, which are the smallest geographical unit reported by the Census Bureau. The block group is the smallest unit for which the Census Bureau reports a full range of demographic statistics. Census tract is a subdivision of a county and is made up of Census block groups. Desktop GIS refers to a GIS that runs on a personal computer. Digitizing is the process of electronically tracing features on a paper map to convert them to features on a computer map file. This is done with a specialized piece of equipment called a digitizing tablet. Geocoding refers to the process of converting tabular location data (for example, street addresses) into accurately placed features in a map file. Many GIS software packages have some geocoding capabilities, although the performance in terms of "hits" (i.e., correctly geocoding a location) is quite variable. Geocoding street addresses is called "address matching." Geographic Information System (GIS) is a computer program that stores, displays, and analyzes data that has a geographic dimension. Geographic feature (also called a map feature) is the fundamental unit of a GIS database. The basic types of features are points, lines, and polygons. Points are used to represent point features, such as a business location, highway access point, or town; lines are used to represent continuous line features such as a road or stream; and polygons are used to represent distinct areas, such as a county, metropolitan area, or soil type. Geographic file (also called a map file) is a computer file that contains both the spatial and attribute data for a set of geographic features. Global Positioning System (GPS) is radio-navigation technology that uses satellite signals to calculate the position of objects on the earth's surface, along with their speed and direction. This technology is used, for example, in "precision farming" to record the exact geographic location of soil quality and other field data. Layer refers to a geographic file, which contains a set of geographic objects (e.g. counties) and their attribute data. A GIS can display many layers at the same time (for example, major highways, school locations, population centers, and county boundaries). Legend is a list of the symbols and an explanation of those symbols that are used to create a map. Map extent refers to the outermost boundaries of the geographic file. Map projection refers to the system that is used to translate the location of a geographic object on the earth's curved surface to a representative location on a two-dimensional representation of the earth (i.e., your computer screen or printed map). Imagine unpeeling the skin of an orange and trying to flatten it out onto a flat surface - it's impossible to flatten it without distorting the shape or area of the skin's surface. In order to overlay two or more layers, the layers must be in the same projection. Map scale is the relationship between the dimensions of the geographic features in a map and the actual size of the geographic object that they represent on earth. This is a number that is commonly expressed as a ratio or fraction. A map scale of 1:100,000 means that one unit of measure on the map equals 100,000 of the same units on the earth. Spatial analysis is the determination of the spatial relationships between geographic features, such as the distance between them or the pattern that they form (e.g., the degree of clustering among businesses). Spatial data represents the shape and location of the geographic features. Spatial data is stored in a digitized computer file. There are three types of digitized spatial data: (1) vector data, which represents spatial data as points, lines, and polygons; (2) raster data, which represents spatial data as cells in a grid; and (3) image data, which stores spatial data as a series of pixels -- usually taken from photographs (e.g. from satellites or airplanes). Thematic map is a map that symbolizes geographic features according to a particular attribute. There are several techniques that can be used to create a thematic map including:
*Many of these terms are taken from: ArcView GIS Means Business by C. Harder, published by Environmental Systems Research Institute, 1997. GIS Software and Data There are many desktop GIS software programs currently on the market. These programs all offer mapping capabilities, but range in terms of their computer hardware requirements and spatial analysis capabilities. GIS programs have become much more user-friendly in recent years. Nonetheless, learning how to use GIS still requires time, effort, and money. The right GIS program will depend on the user's needs, skill level, and willingness to invest time in learning the software program. Many GIS packages come with some amount of "pre-packaged" data, such as geographic files of U.S. counties with basic census variables. The amount and geographic detail of the data varies. Most packages also offer the ability to create your own geographic files. For example, suppose you conduct a business retention and expansion survey and would like to store the information that you collect in a geographic file. Many GIS packages give you the ability to create your own geographic point, line, or polygon file and link this to a database file that contains the attribute data that you've collected. Additional data is available from a variety of sources including governmental agencies (e.g., Census, USGS, EPA) and private firms (e.g., many marketing research firms offer a variety of demographic and market segmentation data linked to geography at very detailed levels). A word of caution about GIS data. Although there are many sources of physical, economic and demographic GIS data, importing and combining this data in a GIS is not always easy or inexpensive. This is because data often comes in different map projections (see the above definition for map projection) or because it sometimes lacks metadata (i.e., documentation of what the data is, the source of the data, map projection, definitions of the attribute data variables, etc.). Gather as much documentation about the data as you can when building your database. A Short List of GIS Resources on the Web
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