September/October 2000

Geographic Information Systems

By Brian Carnahan

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For a long time, questions like "Who lives near this housing development?" were notoriously difficult to answer. The level of data analysis that went into such seemingly simple questions made them too time-consuming for anyone who didn't have ready access to their own research department. Now a powerful new tool called geographic information systems (GIS) makes it much easier.

What is GIS?

Geographic information systems are referred to generically as GIS, while a particular software or system is called "a GIS." A GIS is a database of "spatial" or "geographic" data - anything that can be referenced to the earth's surface, such as housing developments, roads, or census tracts. These have descriptive information, called "attribute data," associated with them. For example, attribute data for a multifamily affordable housing development could include the number of units in the development, or the average rent. Attribute data for roads might include the width of the road or the type of surface, while Census Tract attributes will include the total number of persons or households.

The data - both geographic and attribute - for a GIS come from a number of sources, including federal government agencies like the Census Bureau and U.S. Geological Survey, state, local, and county government agencies, commercial data providers, and proprietary information generated by users as a result of their work or research. The data required by most organizations can usually be found in ready-to-use digital form. Often, however, a project can be completed only by using older hard copy maps and entering attribute data by hand.

While displaying data in map form is its most well known function, GIS is not simply a map-making tool. Maps are a powerful way to visualize information, but visualization is not the sole purpose of GIS. Most GIS software also allows for robust data analysis and database management, setting GIS apart from desktop mapping applications like MapQuest, Yahoo! Maps, and American FactFinder, which are primarily useful for getting driving directions or creating simple maps.

GIS Capabilities

With the appropriate data, most GIS packages will perform a range of analytical functions. GIS utilities allow the user to consider locations, conditions, and patterns. For example, let's say a CDC called "Better Neighborhood, Inc." concentrates on housing in the city it serves; that city is the "location." Using Census Tract data and property parcel information from the county auditor's office, Better Neighborhood can use its GIS to examine the age and value ("conditions") of various housing units. In looking at the whole city, Better Neighborhood can analyze the distribution of housing of a given condition across the city, and the "pattern" it forms.

A GIS can answer a range of frequently asked questions. "Point in Polygon" answers the question "What is located near this?" Buffer Analysis can be used to determine information like "How many houses are located within 'x' miles of a given school or shopping center?" or "How many people in this neighborhood are within 11/44 mile of public transportation?" Using "network analysis" a community based organization dedicated to business development might review the number of cars that pass a particular intersection to determine how many customers a new business might expect to be exposed to.

Using hypothetical questions, GIS can be used to look into the future as well as the present, creating models. Better Neighborhood may want to consider how its investments in housing will affect the citywide pattern of housing, or how property values will change in a neighborhood when units it is constructing are completed. Alternatively, it may want to explore how the density of a neighborhood will evolve as infill development occurs.

GIS also allows for visual presentation - usually maps that illustrate data in a two or three-dimensional form - and database management, including updating, importing, or correcting data.

GIS in Housing and Community Development

As GIS has evolved, it has been heavily used in government and science for land use planning, infrastructure management, and environmental research. In recent years, community development and housing group have begun to use it as well, for tasks like:

  • Site selection: What and who is located near this site? How far is it from important services?
  • Targeting and Resource Allocation: Where is the need greatest? Where is our target population located?
  • Preparing maps showing clients how to get to work locations.
  • Reviewing neighborhood statistics such as the locations of businesses or crime.
  • Producing maps for outreach and communication, showing activities or services area
  • Mapping and analyzing state and local housing and community development data/projects to determine where investments are being made.
Land use planning

Westown CDC, for example, works in neighborhoods in West Cleveland, focusing on safety and commercial and residential development. Chad Dasher, Westown's neighborhood development director, says they use GIS to monitor their programs in the Census Tracts they serve, and to prepare maps for funding applications. To do this, Westown has created its own databases in addition to using data provided by local government agencies and Cleveland State University. Executive Director Lou Tisler says that Westown has also used GIS to explore the distribution of community based assets, such as crime watch groups, and to determine where the CDC is drawing people from for its programs. Westown plans to increase its use of GIS in commercial asset mapping, perhaps looking at businesses in the area.

Partnership for the Homeless, a group that operates homeless shelters in New York City, has used GIS to see where there are gaps in its shelter network. They've also used it in lobbying efforts to figure out which representatives to target.

GIS Software

Each GIS system has a distinct set of features and strengths. Because of the involvement of HUD, Community 2020, a Caliper Corporation product based on Maptitude, comes equipped with information about Section 8 and other housing data. MapInfo has established a sturdy foothold in the business world by focusing on data and analytical techniques useful in business applications. ESRI, through ArcView and Arc/Info is helpful for a broad range of applications. In exploring a GIS, an organization should carefully assess its own needs and how it wants to use GIS, and take into account the availability of data and customer support.

Most GIS software packages are the focus of on-line discussion forums and e-mail lists, which are often accessible through the software manufacturer's web site. Users also occasionally meet in person, as shown by the ESRI regional user groups across the U.S. Participating in an on-line forum will offer opportunities to talk to those using GIS, discover what particular GIS software can do, and what levels of expertise each requires.

Learning More

Most organizations find that it takes time and effort to fully develop the skills necessary to use GIS effectively. Perhaps the most important skills are learning to ask the software the appropriate questions and figuring out the best ways to integrate GIS into the organization's activities.

To start, try local colleges and universities, many of which offer GIS courses - both academic and professional. Penn State University, for example, offers an on-line course designed to provide a foundation in GIS. The University of Southern California, through its Department of Geography, offers a GIS Distance Learning Certificate Program.

Some states, such as Ohio, have programs for GIS support. Through the Ohio Geographically Referenced Information Program (OGRIP), the State of Ohio provides resources for users of GIS and spatial data, and opportunities for GIS professionals to meet and discuss the latest trends. Other states have similar programs. Many local government agencies, such as county auditors' offices and regional planning commissions, are using GIS, and should be able to offer guidance.

A number of publications focus on GIS. Among these are GEOWorld and Geospatial Solutions. These publications provide information about new developments in software, data, and the use of GIS, and provide substantial coverage of real-world GIS applications, giving the novice user an idea of what is possible. Many of the software companies also produce newsletters about their software.

GIS can bolster a community development organization's efforts by enhancing decision-making, resource allocation, and strategic planning functions. In an age when knowledge is power, GIS can offer distinctive tools that enable an organization to gain an edge, provided the organization is willing to make the necessary investment of time and resources to develop a foundation in GIS basics. Westown's Lou Tisler echoes this theme, stating that there is a "learning/exploration curve" involved in integrating GIS into an organization's activities. Yet, according to Tisler, "it would have been great to have [GIS] five years ago."

Copyright 2000

Brian Carnahan is special projects coordinator for the Ohio Housing Finance Agency. The views expressed by the author do not necessarily reflect those of the Ohio Housing Finance Agency.


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