Public Involvement Techniques
4.C.e - Mapping through Geographic Information
What is a geographic information system?
Geographic Information Systems (GIS) combine traditional maps
with layers of related information in an electronic format.
A GIS assembles, stores, manipulates, and displays data that is
identified by location and can relate information from different
sources. Any variable that can be located spatially can be input
to a GIS. Location may be annotated by x, y, and z coordinates of
longitude, latitude, and elevation, or by such systems as ZIP codes
or highway mile markers. A GIS can also convert existing digital
information into forms it can recognize and use. In addition, census
or other tabular data can be converted to map-like form, serving
as layers of thematic information in a GIS.
A GIS stores maps and files layers of information in a way that
makes it possible to perform complex analyses. For example,
a GIS user can query a specific location, object, or area on the
screen to retrieve recorded information about it from off-screen
files. A GIS can also recognize and analyze the spatial relationships
among mapped phenomena to determine adjacency (what is next to what),
containment (what is enclosed by what), and proximity (how close
something is to something else). It is also possible to assign values
such as direction and speed to simulate movement through a network.
GIS also has the ability to produce graphics on the screen or on
paper that convey the results of analysis to people who have input
to and make decisions about resources.
Some of the many broad uses of GIS include:
- Mapmaking - Incorporating the mapmaking experience of traditional
cartographers into GIS technology for the automated production
- Site Selection - Analysis of multiple physical factors when
they must be considered and integrated over a large area.
- Emergency Response Planning - Analysis of the impacts of natural
disasters on surface structures, size of affected populations,
and emergency response time and available routes.
- Simulating Environmental Effects - Realistic, three-dimensional
"before and after" perspective views of the environmental
impacts of a given project.
Source: Geographic Information Systems, U.S. Department of the
Interior, U.S. Geological Survey, http://www.usgs.gov/research/gis/title.html
Why is it useful?
GIS provides a richness of data that is unlike traditional paper
maps. Complex information can be presented graphically in one
place. In addition, GIS maps will typically have more depth of information.
For example, while a paper map may show where toxic sites are located,
a GIS map of the same information will often be backed up by a full
database of information on those toxic sites. Information from a
GIS may also be more current than a paper map. While paper maps
may be updated on a regular schedule (e.g., annually), recent satellite
or aerial photos could be digitized for GIS use to create "up
to the minute" maps of an area.
GIS offers public involvement professionals flexibility in displaying
information. Users determine how and at what levels associated
information is displayed. As a result, maps can be quickly customized
to a particular purpose. Maps can also be used interactively with
the public to gather input and display the possible scenarios resulting
from that input in a real-time setting.
GIS also allows conditions to be analyzed over time. For
example, the San Diego Association of Governments (SANDAG) has been
using GIS for over 25 years to assist in regional and local planning
efforts. By working with its partners, SANDAG has developed cost
efficient techniques to update its land use database on a regular
schedule. SANDAG's GIS website also offers interactive maps that
can be customized to demographic, economic, transportation, and
trans-border themes; downloadable GIS files, and access to printed
Does it have special uses?
GIS can be used in participatory/collaborative mapping.
For example, practitioners and community residents can collaboratively
sketch community boundaries, as seen by local residents and identify
important community assets and liabilities (e.g., cultural resources,
historic sites, toxic sites). GIS also supports "what-if"
scenario planning. Mapping of roads, bus routes, pedestrian paths
and bikeways commonly can help assess those used and/or preferred
by local residents. The results can be overlaid with current and
proposed transportation projects for a quick snapshot of potential
impacts and can be ultimately integrated with new projects. The
following example shows the results of a GIS analysis done by the
Orange County (CA) Transportation Authority (OCTA) to determine
what effect a proposed change in bus service would have on accessibility
to the new service. OCTA used a variety of information, including
population density, land use, and "catchment" areas (i.e.,
the area from which potential riders would be willing to walk to
and from the stop) to develop this analysis. The first figure shows
population accessible to the existing bus system. The second shows
the change in accessibility based on a proposed change. Additional
examples from OCTA can be found in FHWA's Toolbox for Regional Policy
analysis, Orange County Case Study, http://www.fhwa.dot.gov/planning/toolbox/orange_overview.htm.
A GIS can be used to survey residents about their local environments
(cross-link to section in guide on surveys). For example, a the
National Science Foundation has funded a project at the University
of Illinois at Urbana-Champaign to help in understanding of elements
of local environments that are important to people's lives. Through
a face-to-face interview, participants are asked to assess perceptions
about a neighborhood's boundaries, services, strengths and assets,
problems and deficiencies. The interview uses a GIS interactively
to plot responses on a map and prompt follow-up questions, as well
as to present study findings.
GIS also provides information to citizens about community information,
services, and projects. On its communityWEBpages, the City of
Vancouver hosts a "Projects and Construction" section
that includes information about city initiatives, projects, development
proposals, construction and roadwork. Information is searchable
by community, department, project type, street name or location,
and project dates. This information is also mapped using VanMap,
a city-wide map application that also provides information on property
lines, zoning information, sewer and mains, addresses, and public
Other examples of GIS used to provide information to the public
- "Seattle's Neighborhoods - A Graphical Guide to Services
and Activities" maps neighborhoods by census tract. It provides
information on City of Seattle services within tracts, as well
as brief demographic information.
- North Central Texas COG Transportation Improvement Program Information
System provides information about transportation improvement plan
projects in the Dallas-Ft. Worth metropolitan planning area through
an interactive map.
- The EPA Enviromapper maps various types of environmental information,
including air releases, drinking water, toxic releases, hazardous
wastes, water discharge permits, and Superfund sites. Maps can
be created at the national, state, and county levels.
Who participates? And how?
GIS can be used interactively with participants at public meetings,
open houses, and small group meeting. Practitioners may engage
participants as a group or in a one-to-one setting. In addition,
the GIS tool could be set up as a stand-alone interactive display
for meeting participants to review and comment on proposed plans
or analysis. GIS products could also be part of interim and final
project or plan documents.
A GIS tool can also be part of a website. Like many of the
community information services described in the preceding section,
individuals who are computer-oriented are most likely to participate.
Usage would be limited to those with access to computers and Internet
connections. However the public would have the convenience of accessing
information from their homes at any time. Agencies must publicize
the availability of on-line material. (See On-line
A GIS may also be available for plan or text mark-up software.
For example, GIS images of proposed routes or service corridors
may be placed on a website and through appropriate mark-up software,
the public would be able to comment from remote locations at prescribed
review cycles. (See Plan Or Text Mark-Up
How do agencies use the output?
Agencies can use GIS to gather community reaction and obtain
community opinion on projects and plans. Through GIS, agencies
may gain a better understanding of importance of neighborhood/community
elements to public. GIS may also assist with joint-decision making
and empathy building. Interactively mapping scenarios can help all
parties better understand each other's interests and concerns.
Also, because of the electronic interchangeability of the GIS
data files, agencies may save time and resources once a final
concept is approved by using the same materials for the next stages
of the project or plan development using materials developed, in
part, for public involvement purposes.
What are the costs?
Costs to implement GIS systems may be high depending on
the strategic interest and information technology resources of the
agency. In some cases, a project may already have a GIS component.
In addition, agencies may have the necessary hardware and software,
as well as professionals trained in GIS on staff and available to
assist in its use for public involvement. If not, staff training
or hiring consultants may be necessary.
GIS does involve a substantial time commitment on the part of
the agency. Depending on data sources available, maps may have
to be generated for intended purposes. In most case, information
for public display would need to be customized to the particular
If a GIS is to be available via the Internet, some type of outreach
may be beneficial to advertise the service and ensure return
on investment. In addition, set-up and/or licensing costs may apply.
How is it used with other techniques?
GIS can be used to:
What are the drawbacks?
As mentioned above, cost and training may be a drawback to using
GIS. If the hardware, software, and personnel capabilities do
not exist in the agency, or are not being currently employed on
the project, significant costs can be incurred to purchase computer
equipment and train staff, or hire consulting expertise. The availability
of datasets and compatibility of data may also impact the cost of
Because of its electronic format, GIS has the potential for
mass media appeal and distribution. However, agencies must take
care to ensure that false impressions are minimized through accurate
If a GIS tool is to be web-based, project staff needs to consider
that the use of on-line services is limited due to access, expense,
and skill requirements (See On-line Services). As a result, web-based
GIS should be used with other public involvement techniques (i.e.,
meetings, other on-line services).
When is it used most effectively?
GIS is most effective when there is:
- A need to convey complex information graphically;
- Information that can be tailored to particular users or audiences;
- Support or complementarities from other public involvement techniques.
For further information:
- table of contents - next
For more information about the TPCB program, contact Michelle
at FHWA (202-366-9206) or John Sprowls
at FTA (202-366-5362).