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Movementech's Guide to Geographic Information Systems (GIS)
by Dina El-Mogazi


Maps have always been valuable tools for helping people to understand the world around them.  Today, a computer based mapping technology known as Geographic Information Systems (GIS) is revolutionizing the way maps are made and creating new ways for people to view their environment. Movementech is now developing this "cutting edge" tool for use by citizens who are concerned about the environmental quality of their communities.

In January of 1998, Movementech began using GIS as a way of providing grassroots activists with detailed geographic and demographic information about their neighborhoods.  This information  includes statistics on race, income, and age, the locations of industrial facilities, and locations of important community landmarks such as churches, schools, and hospitals. When such information is viewed on a map, it allows grassroots groups to more easily identify the people who will be most adversely affected by an existing or proposed industrial site, for instance young children, impoverished and/or minority populations, or elderly people.  This type of information is invaluable in organizing community support because it allows environmental groups to target the best neighborhoods to approach for membership drives, petitioning, and fundraising, as well as revealing potential locations for meetings and demonstrations.  In addition, GIS is useful in developing broader organizational strategies.

The data for Movementech's maps comes from three basic sources: 1) the US Census, 2) the Environmental Protection Agency (EPA), and 3) the US Geological Survey (USGS).  The information given below will help you to interpret maps and tables that are created from these sources, so that you may use them most effectively.

The Census: A Picture of Your Community

The Census provides a wealth of information on the makeup of a particular community including statistics on race, income, age, educational attainment, poverty status, and many others.  In addition, the Census provides information on the physical boundaries of the political units (such as cities, counties, etc.) that make up a particular area.

Census data provided by Movementech are most often organized by State, County, Minor Civil Division (MCD), and Census Block Group.  Occasionally Congressional District, Place, and Metropolitan Area will also be used.

Excepting congressional districts and metropolitan areas, all geographic political and statistical areas are based upon the 1990 Census.  (Because this census is conducted only once every ten years, the most recent data available is from 1990.)  The congressional districts are for the 105th Congress (January 1997 through January 1999) and the metropolitan areas are defined as of June 30, 1996.  The boundaries for all of these types of areas  are taken from TIGER/Line 1995 files (see definition below).

Census Definitions:
  •  Block Group (BG) This is the smallest unit for which the US Census tabulates data.  Usually it is equivalent to a neighborhood, but in less populated areas it can cover a much larger land area. A block group is a subdivision of a census tract.
  •  Census Tract A subdivision of a city or county with that represents a relatively homogeneous population with respect to economic status and living conditions.  Census tracts usually contain 2,500 to 8,000 residents.
  •  Congressional District (CD) An area established by State officials or the courts for the purpose of electing a person to the US House of Representatives. Within each State these areas contain, as nearly as possible, an equal number of people.  After each census, the boundaries may change.
  •  Metropolitan Area (MA) An area with a large core population (usually a major city) plus nearby communities (usually suburbs) that have strong economic and social ties with the core.
  •  Minor Civil Division (MCD) A governmental unit that is the subdivision of a county.  These may be called towns, townships, or districts depending on what State is being mapped.
  •  Place  A concentrated population (usually a city, town, or village) that is identified by a particular name and falls within set boundaries which may be distinct from MCD's.
  •  TIGER database TIGER (Topologically Integrated Geographic Encoding and Referencing System) is a computer file that contains geographic information representing the positions of roads, rivers, railroads, and other map features that are used in the census.

EPA Data: Keeping Track of Emissions and Hazardous Waste in Your Neighborhood

The Environmental Protection Agency (EPA) maintains several different databases on the industrial facilities that it regulates.  These databases include a wealth of information that can be put to use by concerned citizens and grassroots organizations including emissions records, violations, facility ownership, and more.  The facilities appearing on Movementech's maps are designated by symbols that indicate which EPA database the facility reports to.  (Some facilities report to more than one database.)  A list of the facility types found on Movementech's maps and their definitions are provided below.

Facility Definitions

  •  Air Facilities  Air Facilities data comes from the Aerometric Information Retrieval System (AIRS).  This database stores information on air quality and point source emissions for selected sites.  Industrial facilities that emit more than 100 tons per year of certain key pollutants (for instance particulates, sulfur oxides, volatile organic compounds, and others,) or more than 5 tons per year of lead, are required to report annual emissions data.
  •  Hazardous Waste Facilities   Hazardous waste facility information comes from the Biennial Reporting System (BRS).  The BRS system contains information submitted every other year by facilities that are regulated under the Resource Conservation and Recovery Act (RCRA). These facilities either treat, store, dispose, or generate hazardous waste in significant quantities.  The BRS data for Movementech's maps comes from the year 1993.
  •  RCRA Violators   The Resource Conservation and Recovery Act (RCRA) regulates generators, transporters, treaters, storers, and disposers of hazardous waste.  This act covers both large, and small quantity handlers of hazardous waste and includes all kinds of operations from gas stations to major industrial sites.  Because there are so many RCRA-regulated facilities, Movementech usually maps only those facilities that have been found to be in violation of the RCRA.
  •  Superfund/CERCLIS Sites   The Comprehensive Emergency Response Cleanup Liability Information System (CERCLIS) supports EPA management and oversight of the Superfund program.  The data system has two purposes: 1) to maintain an inventory of abandoned, inactive, or uncontrolled hazardous waste dumps, and 2) to report the status of the clean-up of these sites. The National Priority List (NPL) sites have been selected by the EPA as posing the most serious environmental threat and requiring immediate clean-up. These are designated with an "S" for Superfund.  The remaining sites are designated with a "C" for CERCLIS.
  •  Toxic Release Inventory   The Toxic Release Inventory (TRI) contains data submitted to EPA by regulated facilities concerning chemicals and that have been determined to be toxic to humans.  This data includes the amount of each chemical released and the medium (i.e. air, land, or water) that they are released into.
  •  Wastewater Discharge Sites   Data for theses sites comes from the  Permit Compliance System (PCS).  This database contains information on permits for discharging wastewater from industries and municipal treatment plants throughout the nation.
USGS Data: Important Landmarks in Your Area

Schools, churches, and hospitals are special places in a community where citizens congregate and communicate with one another.  These sites provide highly visible meeting places for grassroots groups and also serve as good places for networking with other community organizations. Data for schools, hospitals, and churches comes from the Geographic Names Information System (GNIS), a publication of the USGS.  GNIS contains names for all known places, features, and areas in the US that are identified by proper name.

A Word About Accuracy

Geographic Information Systems rely heavily government data.  These data are prone to error in many ways.  The U.S. Census, for example, is collected every 10 years.  This report utilizes 1990 data, which, as a result, is 8 years out of date.  The next census data set will not be available until approximately 2002.  This means that care should be taken in interpreting population data because population shifts which have occurred at the local level since 1990 will not be detected.

We have also detected errors in the accuracy of geographic coordinatedata for schools, churches and environmental facilities.  This means that some sites will be located incorrectly on the maps.  In addition, EPA and US Geological Survey data contain considerable gaps.  For instance, some types of facilities such as municipal incinerators, are not regulated by the EPA, and therefore usually don't appear on the maps. We have also discovered that some schools and churches are simply not present in the data.  In some cases, where time permits, we are able to find the locations of missing facilities, churches and schools through alternative data sources such as state environmental agencies, phone books, and local maps.

Some errors have also been found in "value added" commercial boundary data such as that provided by Wessex.  Some county boundaries, for example, do not correspond with municipal boundaries and sometimes whole municipal boundaries are missing.  Movementech is concerned about these problems but largely we must rely on local knowledge in order to correct them. If you are aware of any errors in maps and data we've provided, please do not hesitate to contact us and help us correct these errors.

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