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Section 16. Geographic Information Systems: Tools for Community Mapping

  • What is GIS?

  • Why would you use GIS?

  • When would you use GIS?

  • Who should use GIS?

  • How do you use GIS?

Petersonville was growing. New developments were going up on the edge of town, old buildings in the downtown area were being renovated, and business was booming. Unfortunately, traffic was also booming, with an alarming increase in accidents.  Not a day seemed to go by without someone being seriously hurt, and fender-benders were becoming so common that they hardly attracted any attention. A town that had gotten by for decades with only two traffic signals clearly needed more.

The question was where to put them. The Town Planner, using Geographic Information Systems (GIS) software, created and analyzed maps that showed where accidents had occurred, the frequency of accidents in different areas of town and at specific intersections, and the locations of the most serious accidents. Using that information, she could see that placing traffic lights at four key intersections, and putting up stop signs at three more, might reduce the number of accidents, and should also cut down on serious injuries. The lights and stop signs were put in place, and the Planner’s analysis proved to be correct.  Traffic wasn’t made any lighter by the controls, but its consequences were a lot less costly.

Often, community problems have to be examined geographically. Where is youth violence most likely to break out? Which neighborhood needs the new elementary school?  Why do people in a certain rural area have more heart attacks and strokes than those in nearby areas? These kinds of questions can often be answered by looking at a map that contains more than just the location of towns, roads, water, and political boundaries (county lines, state borders, etc.). These maps can be constructed using GIS –Geographic Information Systems. This section describes GIS, and discusses how you might use it in your community to advance your own work.

What is GIS?

GIS is a method of digital (i.e., computerized) mapping that can show you where particular people, events, things, or conditions are, and give you other information about them as well. It links data to its geographic location.

GIS – Geographic Information Systems – is sometimes confused with GPS – Global Positioning System – because of the similarity of their initials.  A GPS is an entirely different device that tells you, by beaming off a satellite, where you are on the face of the earth.  Unlike GIS, GPS devices don’t need a separate computer or software – most are handheld, or are built into a car – and are far less likely to be useful to health and community workers, unless they have to make their way to hard-to-find places.

We can look briefly at how GIS works by using the traffic example above.  The planner started with a GIS computer program that creates maps from data that’s fed into it.  It displays “layers” of geographic information, usually starting with a map of the geographic area you’re interested in – in this case, a street map of Petersonville. The locations of all accidents in the past six months, for instance, would be another layer; the locations of accidents that resulted in hospitalizations during that same period might be a second; the locations of traffic controls (warning or stop signs, flashing lights, etc.) could constitute a third.

Imagine that the street map is drawn on paper, and the other layers are drawn on transparent plastic to exactly the same scale. You could place one or more of the layers over the street map and immediately see where accidents happened, where they were clustered, where the serious accidents were most likely to occur, what effects traffic controls seem to have, etc. That’s exactly what is done with GIS, but far more quickly and more accurately than a hand-drawn map would.

GIS can do the same with all kinds of information, as long as it has a geographic reference (i.e., as long as you can specify its location).  In order to function, however, GIS systems have basic needs:

  • Hardware with enough power to run the GIS software
  • GIS software with the capabilities you need
  • Accurate data, in a form that can be fed into the software program
  • People trained to use the GIS system

GIS is often extremely useful in health and community services. It can track the spread or incidence of diseases, or of medical or social conditions.  It can show you where people with particular characteristics – age, ethnicity, income level, education level, etc. – cluster, where certain things happen or are likely to happen, the pace and direction of development, the spread of pollution, buying patterns, traffic patterns, the location of current and former buried utility and water lines -- in short, just about anything you’d need for assessment, planning, or evaluation purposes, as long as it had a geographic component and was accurately recorded.

The best way to understand exactly how GIS works, and how it can work for you, is to get a demonstration from someone who’s good at using it.  You may be able to do this at a local educational institution (many colleges and universities offer GIS courses, or have their own GIS capability), or a GIS professional or retailer may be willing to give you a demonstration in hopes of selling his or her services or products.

If you need it often, you might want to buy appropriate GIS software for your organization, learn to use it, and create your own GIS maps whenever it’s necessary.  If you only need GIS occasionally, it might make more sense to have a GIS professional do the work for you.  It’s sometimes possible to get GIS services free, either as a public service, or because someone – often a university or government agency – is paid to provide it to nonprofits and community groups.  When that’s not available, you may be able to find affordable services from a firm or agency that uses or specializes in GIS.

We’ll look at all of this more closely in the remainder of this section. To understand the concept fully, let’s start with regular maps, the ones we all use.

Everyday, spatial mapping

We all know what a map is.  In its simplest form, it’s a picture of a place, usually seen from above. A map can picture an area as small as a tiny printed circuit, or as large as the solar system, but most of the maps we use in our daily lives cover a country or a state or a town.

These maps give us spatial information: they tell us where things are.  They include such physical features – actual places you can experience in reality – as towns and cities, main roads, and bodies of water.  If the map is more complex, it may also locate mountain ranges and peaks, railroads, elevations (height above sea level, indicated either by shading or by contour lines), or other elements of the landscape.

Our maps also include political features – imaginary lines imposed on the landscape by people. These include the boundaries of towns, states, countries, national and state parks, historic districts, watershed areas, conservation land, and other areas that are political units or that have been set aside by government or others for a particular purpose.

Finally, the maps we use every day include the names of important physical and political features. The names, like political boundaries, are artificial and invisible, but they are tremendously important in making a map useful. They locate us in our world, and tell us where we are in relation to other places whose names we know.

GIS mapping

There are other maps that many of us are exposed to. In newspapers and news magazines, on some TV shows, and especially in places like the National Geographic magazine and website we may see maps that show more than just the normal physical and political information. (Perhaps the most familiar of these are the weather maps that TV weather persons refer to.)

Some of these maps may simply show more detailed spatial information. They point the way to particular kinds of places, or tell more about the landscape than an average map might. 

Some examples of the physical information on such a map might include:

  • Water mains, phone lines, or other buried networks.
  • Areas of coastal erosion.
  • Sites of historical interest.
  • The location of different types of vegetation – hardwood forest, evergreen forest, grasslands, meadows and overgrown fields, alpine vegetation, etc.
  • Commercial and residential areas

Although beyond what’s shown on most highway maps, all of this information can be found by going to the place in question and looking around. There is much information that isn’t visible in this way, however. A good example is the location of traffic accidents referred to in the introduction to this section.That’s information that is tied to specific places, but you wouldn’t know that just from going there. Unlike spatial information, it’s more than a picture of the landscape: it tells you what happened there as well.

In addition to showing you what happened where, a map can tell you about the lives of the people who live there, the geology or soil chemistry of the area, the ranges of its endangered species, the spread of disease in its human or animal populations, or the rate of its development. By using different colors or patterns, just as they often do to distinguish between states or countries, maps can show many kinds of differences:

  • Levels of population density in different parts of a city
  • Where different ethnic or racial groups are concentrated
  • Income levels in different areas
  • Increases in housing starts for various areas
  • Current ranges of endangered species
  • The frequency of particular diseases or conditions in various regions, towns, neighborhoods, or even city blocks
  • The proportion of children under 18 in different school districts

These are the kinds of maps that can be created using GIS software and the appropriate data.

Two kinds of data are necessary:

  • The desired physical and political features of the map you want. Depending on the software and the nature of the data available, this might be scanned in, programmed in, or downloaded from the Internet or from a CD.
  • The location information about the other features you’re interested in. Like the spatial information, this has to come from somewhere. It might be downloaded from a database, the Internet, or a CD, or entered by hand from information you’ve gathered yourself, but the data have to exist to begin with, and they have to be accurate if your analysis is to mean anything.

Let’s say you’re concerned with the effects of spreading industrial development on the health of people in the area where it’s taking place.

 Some of the data that you might want to enter into a GIS system could include:

  • A map of the area with which you’re concerned – a county, a rural area, a city, a specific part of a city
  • The current industrial and residential sections of that area
  • Locations where residential and industrial development have taken place in the past two years, or five, or ten, or all of these
  • Projected industrial and residential development within the area you’re studying
  • Population density
  • Prevailing wind and drainage patterns
  • Incidence of particular medical problems in the area – specific diseases, birth defects, etc.
  • Location of drinking water sources, identifying those that have tested safe and those that have not

Each of these pieces of information would be a GIS map layer.  Whichever of the layers you chose, or all of them, could be laid one over another, so that many different pieces of information could be viewed at the same time. In that way, you can examine just how particular factors overlap or interact with one another.

Components of GIS

There are, as we’ve mentioned, four requirements for using GIS effectively:

  • The appropriate hardware. You need a computer with enough memory, video capacity, and hard disk storage space to run the GIS program you want to use. As we’ll see when we discuss software, just how much computing capacity is necessary depends on what kind of software you choose, and on whether you make your own GIS maps or only need the capacity to view those that are created by someone else.
  • The appropriate software. GIS software ranges from simple viewers, which allow you to view, but not create, maps, to map-creation software that can display a small number of layers, to powerful applications that can handle and display enormous amounts of data. Some software can create and display GIS maps from a website, making them accessible to large numbers of users at a time. Other types of software can embed GIS capacity into non-GIS applications, so that non-GIS software programs can use the data stored in them to create GIS maps. The software you need depends on what you want to do with GIS, how much you intend to use it, and how important it is to the overall functioning of your organization or project.

    Good GIS map-creation software, regardless of how powerful it is, should include:

    • The ability to enter and work with geographic and location information – street names, political or other boundaries, etc..
    • A database management system, to organize and manage information.
    • A map creator that makes maps that are easily viewed, rational, and simple to interpret and analyze.
    • A simple and usable graphical user interface (GUI).

    The graphical user interface is what you see on the screen when you run a computer application. It contains the various toolbars and controls for the software, and shows you the results of what you’re doing. How the GUI is set up has a lot to do with how easy a program is to use. If the commands and buttons are intuitive – that is, if they correspond to what most people would naturally do – then the program will usually run smoothly. If the commands are unnecessarily complicated or odd, most people will have some trouble learning and using the program.

    GIS software can be complex, since it involves both graphics and large amounts of data. For that reason alone, a simple and easy-to-use GUI is crucial in making the software available to anyone who needs it.

  • The necessary data. GIS software can’t create a map unless it has the information to do so.This comes from the data that the software has to use. There are two kinds of data necessary:
    • Spatial data.This is information that specifies features that actually exist or are imposed by people on the ground in the area you’re interested in. These might include roads, rivers, political boundaries, towns, coastlines, etc. Spatial data can also locate objects – buildings, open spaces, forest, etc.
    • Attribute data. These are data that give you information about the area you’re interested in and the people and features that exist there. Some possible data here are who lives where (and how many of them per square mile or kilometer), where different kinds of businesses are concentrated, how land is used, aspects of the population (languages, race, the incidence of particular medical conditions, income, education, crime rates), trends and changes over time (tracing the conversion of farmland to housing developments over 10 or 20 years, for instance), transportation routes, recent development – anything that provides you with useful information.
  • People trained to use the system. Software, no matter how good, is only useful if it’s used properly, and if all its abilities are taken advantage of. In order for that to happen, the people using it have to be familiar with all its possibilities, and have to know how to get the most out of it. Some simple GIS software may be easily learned from a manual by anyone who’s reasonably comfortable with computers and maps. More complicated software may require something more – a tutorial program, help from others who’ve used it, or even a full-fledged training or a college or university course. Whatever software you choose, make sure that you have the necessary understanding to use it well.

    Using the system includes not only using the software, but understanding what you’re looking at and interpreting the patterns that appear on the maps you’ve created. The maps give you information, but you have to interpret that information in ways that lead to some better understanding or some action that will address that with which you’re concerned. In the traffic example at the beginning of this section, for instance, the Town Planner analyzed the map information to decide where to put traffic controls.

    The analysis in this case was simple – it was largely a matter of looking at the maps and drawing logical conclusions, since the serious accidents were clustered in specific places.  In some cases, where there are hundreds or thousands of pieces of information involved, the data has to be analyzed by computer. Some high-end GIS software programs have the capacity for this type of analysis, and most GIS software can perform some level of analysis.

    Only if you analyze the data correctly will it help you in understanding trends, managing needs, addressing and improving current conditions, and planning for the future.

Why would you use GIS?

Clearly, the use of GIS requires some expense and preparation. Why would you go to the trouble?  There are actually a number of good reasons. GIS is a powerful tool that can be used for analysis and assessment of the community or of an issue, and the planning, implementation, and evaluation of an intervention or initiative.

Some of the advantages of using GIS:

  • It can help you determine how seriously an issue affects an area or the community as a whole. The layering of several factors on a map can give you a clearer picture of, or new insight into, the nature, extent, and distribution of a condition, and make it easier to compare it with other issues in the same area.
  • It can clarify the relationships among several factors, populations, or issues. Often, being able to see a picture of the interaction of various factors makes it much easier to understand how they influence one another.  Relationships jump out at you from a map in a way that they don’t from a column of numbers.
  • It can demonstrate how differently an issue affects different populations or geographical areas.This can be important information for a number of reasons.  It can pinpoint problem areas or populations, give clues to the origin or cause of a condition, and suggest means of addressing the problem.
  • It can show you exactly where to concentrate your efforts. If you’re concerned with AIDS prevention, for example, GIS can help to identify areas where the population is at the highest risk, and where outreach, clinics, needle exchange, or other preventive measures would do the most good.
  • It can help you better understand the area or community in which you’re working. A GIS map can show a large amount of information all at once.  It may, for instance, illustrate for a targeted neighborhood abandoned buildings, population density, and the age, income, ethnicity, and education level of the population.  The ability to see all these factors together can be a powerful tool for assessment and planning.  It can also confirm or negate impressions or unsupported assumptions about an area, giving you a clearer and more objective view upon which to base conclusions.
  • It can allow you to isolate and examine individual aspects of the situation or area. By choosing layers to display, you can look at the interaction of various pairs of factors, or just look at the geographic spread of specific ones.
  • It can provide a picture of the community’s or area’s assets and weaknesses. Seeing these graphically can make clear just how many positive aspects there are to the community, and how much already exists that can be mobilized to address problems.  At the same time, it shows where assets are lacking, and can suggest ways to deal with that.
  • It can help in designing, implementing, and evaluating interventions. GIS provides the evidence on which to base planning and implementation decisions, as well as a basis on which to justify those decisions to funders and policy makers.
  • It can show you change over time. Comparing two maps, one showing the incidence of a condition two years ago and the other current, can help you understand where and how your efforts are succeeding and where and how they’re not. By the same token, by using GIS maps you can compare your work to that of others, and consult with others if they seem more successful.
  • GIS is by far the quickest and most efficient method of creating maps and similar graphics that provide a picture of not only the geographic, but of the social, demographic, environmental, political, and other aspects of an area as well. GIS systems can gather and present information graphically in a variety of ways, change it at command with just a few mouse clicks or keystrokes, reorganize it, and manipulate it, creating each time a graphic representation that clarifies conditions and relationships. If you need this kind of information (and not everyone does), GIS is the best way to produce it.
  • GIS maps make powerful presentation tools. For most people, visual representations are easier to grasp than columns of figures or oral presentations. GIS maps can provide simple, understandable explanations of sometimes complex situations and issues, and make strong arguments for courses of action.
  • Perhaps most important, GIS maps can help influence policy. Policy makers, particularly elected officials, often know relatively little about the issues their decisions affect.  Because they are so powerful at representing conditions in an area, GIS maps can help policy makers understand issues more clearly, and lead to policies that address reality in rational ways.

When would you use GIS?

In general terms, there are three times in the life of a project, intervention, or initiative when GIS can be most useful: before you begin, to help with community assessment and understanding the issues; during the planning phase; and while you’re evaluating and refining your work. 

More specifically, GIS can be used:

  • When you’re determining what the most important issues are. GIS maps can show the extent and intensity of issues or conditions in the community, and sometimes give clues as to how to address them.
  • When you’re taking stock of the community’s assets and challenges. GIS can demonstrate the extent of the assets the community already has to address its problems, and where those assets are located in relation to where they might be needed.
  • When you want to locate, or determine the existence of, a particular constellation of factors in a population or an issue. Sometimes, often because of a funder’s priorities, it’s necessary to determine whether there’s a need for specific services in your area. You might need to know the numbers of certain people – Hispanic high school dropouts, employed Asian women with limited English ability – or information about certain conditions – unemployment among people with no college background, high blood pressure among males over 40, etc.
  • When you want to understand the scope of an issue. A GIS map may make it clear that a particular issue is too big for your organization to tackle wholesale, and persuade you to choose to narrow your focus to a specific neighborhood or population, or to take on a different issue that’s more manageable.
  • When you’re deciding where, and on whom, to concentrate your efforts. Unless you’re a very large organization with significant resources, it’s likely that you have to consider carefully what you can do with the funding and personnel you have. GIS, by providing hard evidence, can be a very effective planning tool to identify the location(s) and population(s) where you can do the most good within your capacity.
  • When you’re looking at changes that have taken place over time. There are really three reasons you might want to do this:
    • To track the course of an issue or condition from some time in the past until the present, to determine in which direction it’s moving.  Is homelessness in the community increasing or decreasing?  Is a particular medical condition more or less common than in the past?
    • To identify changes in demographic and other factors that may influence how you work in the community. Has there been a shift, for instance, in the major ethnic groups in the community?  Has population density changed, or has the median income grown?
    • To determine whether your work has had the desired effect. Has there been a significant decrease in teen pregnancy in the area you work in (compared to neighboring areas) since you started your teen pregnancy prevention effort?  Has there been an increase in the number of teens who have received education about birth control and the responsibilities of parenthood?
  • When you’re trying to influence policy.  At legislative hearings, in private meetings with policy makers, or in the media, GIS maps can show, often much more simply and clearly than an oral or written explanation, what conditions really are in an area or community. They can not only influence policy makers’ decisions directly, but can help mobilize public opinion as well.

Who should use GIS?

In order to use GIS effectively, as we’ve discussed, you need software, the proper training or people who’ve had that training, and access to data.  Any or all of these may be a problem for small community-based or grass roots groups.  Many colleges and universities, however, offer GIS courses, and may welcome the opportunity for students to solve practical problems by conducting GIS studies for community groups and organizations, or may offer GIS mapping as a community service.  Some local, state, and federal government agencies may also offer services to the public or to nonprofits either free of charge, or for a small fee.  There are also numerous private firms that offer GIS services; while their fees are higher, their services are often more wide-ranging than those available from public sources, and some may offer pro bono (i.e., free) services to nonprofits or community groups.

The lesson is that you don’t necessarily have to have your own GIS capability in order to take advantage of the technology.  Depending on your finances, you may have a number of providers to choose from.  Especially if your need is likely to be one-time-only, farming out your GIS needs may be your best course of action.

At the same time, be aware of whether you actually need GIS to find out or demonstrate what you want.  If the amount of data needed is relatively small, and not exclusively tied to one place, GIS may be unnecessary.  If you can come up with the same information by using available data – Census tables, for instance – in an afternoon, it’s probably not worth it to employ GIS.  Your results will be less dramatic if they’re simply numbers on paper, but they’ll be just as accurate, and won’t take you any longer to get.

The bottom line here is the bottom line.  Consider your resources.  Even if you can afford a GIS software package, and you have the hardware to run it, do you have the staff time available for someone to learn the program (which may involve a college course, or a several-week training) and run it?  Remember that the person who does that will be taking time away from some other job in the organization as well as spending time on GIS.  It may be cheaper in the long run to contract for GIS when you need it.

The list of those who might benefit from the use of GIS mapping is long. In fact, news organizations and think tanks use it all the time, as do weather forecasters, space scientists, and the intelligence community. 

For the purposes of Community Tool Box users, a logical short list might be:

  • Researchers and participatory research teams
  • Community coalitions
  • Health and human service organizations and agencies
  • Environmental organizations
  • Educators
  • Policy makers
  • Advocates (i.e., those who want to influence policy makers)
  • Community activists
  • Watchdog organizations
  • Community developers and community development agencies
  • Local officials and community planners

How do you use GIS?

GIS is a visual, graphic process.  As we’ve mentioned, a good way to understand it better is to actually observe it under the eye of someone who can show you what it can do. If the material is hard to visualize, you may want to visit a site that demonstrates or explains the process, and gives visual examples. Two of the best are Geographic Information Systems and Introduction to Data Analysis Using Geographic Information Systems.

Whether you do your own GIS mapping or hire someone else to help you, you still have to understand how to use the system to find out what you need to know. The steps sound simple: frame your question, collect the data, integrate it, make your maps, and analyze the results. Let’s look at each step individually.

Much of the following material is adapted and/or based on Introduction to Data Analysis Using Geographic Information Systems, by Daniel L. Falbo, Lloyd P. Queen, and Charles R. Blinn, on the website of the University of Minnesota Extension Service.

Frame the question (decide what it is you want to find out).

GIS is tied to geography: that’s the point. The questions you might want to answer will therefore have to do with place. What are, were, or will be the conditions, or what’s happening, has happened, or is going to happen in a specific place, and what does that mean?  There are, fundamentally, five types of questions that GIS can help you answer – and you may be asking all five at the same time.

  • What actually exists at a particular location?  Here, you’re not necessarily looking for reasons, but simply for what’s there. A land trust might ask where all the undeveloped land in its community is, for instance.  A homeless shelter might want to look at all the affordable housing in a neighborhood.
  • Where is the best place (or worst place) to put something or someone?  A school district may look at the pattern of Hispanic residence in a community to see which schools might need bilingual or ESOL (English as a Second or Other Language) programs.  Gang territories or locations of youth violence might help an organization decide where to place street outreach workers. A geological map can help community planners decide where to dig town wells, or where it’s safe to allow a factory that releases certain chemicals into the soil.
  • What changes have there been in a specific period of time?  You might ask this question as part of a community assessment or an advocacy campaign (Has an issue become more or less serious in the past two years?), as part of a planning process (Has the population changed over time, so that you should use an approach other than the “standard” one?), or as part of an evaluation (Has our work had the desired effect on the community?).
  • What patterns can we find in the geographic data?  Are certain health conditions concentrated in particular areas, for instance, and what else do those areas have in common?  Where do low-income populations live, and how close are those areas to public transportation?

John Snow, a London physician, famously mapped the locations of cholera cases during a 19th century epidemic.  From his map, he determined that a particular water pump, which brought polluted water from the Thames River, was part of the cause of the problem.  When the pump handle was removed, the epidemic eased; Snow had found a pattern in the geographic data that made it possible to change conditions and save lives.

  • What can we predict if we change pieces of data?  What might be the effect on groundwater of building industrial plants in different places?  Would changing traffic patterns or controls make traffic flow more smoothly?  What bus routes would reach the most potential riders? By plugging in different information, you can look at the effects of different scenarios, and use the possibilities to help make decisions that affect the quality of life in the community.

As you decide on which, or which combination, of these questions you’re interested in, consider this:  Maps are fun for many of us.  They’re almost always interesting, and often beautiful.  You might easily be tempted to try to fit as much information as possible into a GIS map project.

In some cases, this isn’t a bad idea.  As we’ve mentioned, a GIS map can often offer new insight into a problem or its solution, and that insight may come from an unexpected direction.  The more information the map can show, the more likely it is that hidden relationships – if there are any – will come to light.

On the other hand, data may be difficult to find, or may have to be entered into the system by hand at the cost of many hours of labor. You may be paying a consultant or firm to make the maps for you.  If the data is easily available and easily fed into the system (and you can afford the expense if someone else is doing the work), then, by all means, examine the situation from as many different angles as you can.  But if data gathering, data entry, or the cost of the process strains your resources, it makes more sense to keep it simple.

Gather the data.

“Garbage in, garbage out” was an early expression attached to computer operations. GIS, like any other computer application, is only as good as the data it has to work with. If your data is out of date, incomplete, or inaccurate, you won’t get a current, complete, and accurate picture of the area and issue you’re examining.  For that reason, it’s important to consider the source of any data that you get from outside your organization, and to pay attention to the reliability of any information you’ve collected yourself.

There are, as explained above, two types of data: spatial, or map data, which locate geographic areas and objects, including political and other boundaries; and attribute data, which tell you about those areas and objects. The data needed, then, include the actual map information for the whole area you want to look at, broken down in the ways that will give you the information you want (e.g., into counties, census tracts, neighborhoods, city blocks, towns, etc.); and the information that describes and differentiates the people, environment, or activities in that area.

Some of the most common types of data that might be of use to Tool Box users are demographic, those that identify people in an area by different categories or levels of categories.

Typical examples include:

  • Race or ethnicity
  • Income levels
  • Education levels
  • Voter registration (either registered vs. unregistered, or registration by political party)
  • Age
  • Health insurance

Another common type of data concerns the location and frequency of particular events or conditions:

  • Traffic accidents (can also be differentiated by whether or not injury or death occurred)
  • Incidents of violence crime (by number of incidents, or by type of crime)
  • Cases of a particular disease or medical condition
  • Location of housing identified as substandard
  • Gypsy moth infestations
  • Polluted groundwater

The list could go on. There are as many possibilities for data that might be entered into a GIS system as there are possibilities for a condition, an event, a population, or a situation to be connected with a place.  Various groups use GIS data to study consumer buying patterns, the spread of weapons around the globe, oil exploration possibilities, endangered species protection – practically anything you can think of.

Data sets take a variety of forms. They may be in the form of tables or lists; pictures, charts, or other graphics (including maps); or 3-D images. They may be in print, slides, computer files (spreadsheets, databases, graphics files, etc.), or files downloaded from websites. Much is free, but some you may have to pay for, especially if you get it on CD.

Your data can also come from a variety of sources. The most easily accessible is data you have collected yourself. In some cases, depending on how it’s stored (in a common data base, such as Microsoft Access, for instance) and the nature of your software, you may be able to load it directly into the GIS system.  If it’s on paper or in a word-processor file, you may have to type it in.  Similar data may be available from other organizations, or from local officials or agencies.

For the U.S., much state and federal data are available on line. A great deal of demographic data, for instance, is available from the Census Bureau where you can also find TIGER (Topologically Integrated Geographic Encoding and Referencing system) maps and products. There are many other places on the Internet from which data can be downloaded.  Many municipalities and government agencies have their own websites, or websites for specific programs or initiatives, that may contain data you need, and there are numerous commercial data sources easily findable on the Internet as well.

At Geographic Information Systems you can find links to a large number of data sources, both free and commercial. The University of Arkansas offers links to many GIS data sources from each of the 50 states. Stanford University offers even more, including international data. The U.S. Geological Survey is another source, as is the U.S. Fish and Wildlife Service for environmental data.

Integrate the data into the GIS system.

This means entering the data in a format recognized by the software. It may involve typing in a table, loading data off a CD, downloading from the Internet, or importing data from a computer file. Not all software will necessarily accept data in all of these ways, and so you may have to change the format before you can enter what you have.

A few words about software.  As we’ve discussed briefly, GIS software can range from the very simple – a viewer that allows you to see and manipulate GIS maps, but not to create them – to powerful programs that allow the creation of a very large number of layers, that will file and work with enormous amounts of data, and that will store as much map information as you’ll ever need.  If you buy software at all, rather than farming out your GIS function, it’s important, as with any purchase, to determine your current and future needs, decide what you can afford, and get some advice about what works well.

One consideration is how much extra work you’ll have to do to enter data.  Map information, for instance, may need to be converted to a digital format, if you don’t have access to maps that are already digital.  The process is fairly time-consuming, and may require extra hardware and/or software.

Other data – tables, charts, graphs, lists, statistics, etc. – have to be entered as well.  Will the software accept data from other applications, such as Access?  Can data be easily entered from the keyboard, or does it have to be translated in some way first?

What kinds of math functions will the software perform? Most will perform at least simple math functions, and will calculate such things as population density, if they have data that they can translate to both the population and the size (in square miles, for instance) of a particular place.  Some will do a lot more, both separating and integrating many levels of maps.

How does the software make its maps?  There are two kinds of mapping: vector, which constructs maps through a series of points and lines; and raster, which uses polygons (many-sided geometric figures).  Each is better for certain applications.  Some software incorporates both, and some does not.  Most software contains methods of integrating the two.  The technical differences are too complicated to explain here, but the software companies, colleagues familiar with GIS, or the Internet can help you understand the distinction and decide what your needs are.

There are four major software producers.  (This doesn’t necessarily mean that their products are the best or the cheapest, but simply that they are the largest and most widely used brands.)  They are ESRI, which sells the Arc line of products; Intergraph, whose GIS software goes under the name GeoMedia; Pitney Bowes; and Autodesk, with basic GIS software called Map3D.  There are also public-domain GIS programs available free on the Internet, and smaller software manufacturers whose products or support may be best for you.

Make your maps.

Once the previous three steps have been completed, actually making maps is the business of the software. The difficulty comes in deciding exactly what area to map – you may have to look at neighboring, or even far-away areas that have some effect or influence on your area or on the issues you’re concerned with – and what you want your map layers to be.

Suppose you’re looking for patterns in the frequency of a health condition. You’ll want to know the basic information:

  • Is the condition more common in some parts of your community or region than in others?
  • Are there places where it’s extremely widespread, compared to the rest of the area, or places where it’s practically nonexistent?
  • How does the frequency and distribution of the condition in your area compare to the same statistics in other areas?  Is it “normal,” or unusual?

Then, assuming there are patterns, you’ll want the layers that might help to explain them:

  • Income. Is the condition related to poverty or to relative income?
  • Race/ethnicity. Might there be a genetic connection?
  • Culture/language. Could it be connected to lifestyle or diet? Might it have to do with not being familiar with some basic protective action (e.g., vaccination)?
  • Type and location of industry in the area. Could there be an environmental aspect?
  • Local wind patterns. Where does the air these folks breathe come from, and what’s located there?
  • Housing conditions. Another environmental possibility
  • Former sites of industry or industrial dumping
  • Source of drinking water

These are by no means exhaustive lists. The actual situation, especially with an understanding of the context – the history of the condition in the area, for instance – could suggest many more layers.  Deciding what the necessary layers are – particularly if you’re limited by your software or by resources – is a crucial part of using a GIS system.

Analyze the results. Once everything you’ve specified has been mapped, you can combine different factors to see how they’re related. Here’s where relationships can jump out at you from the map. If, for instance, all the areas where the medical condition used as an example above is most common are areas occupied largely by a particular ethnic group, the overlap will be immediately apparent.  If there are certain kinds of industrial plants nearby, that also will be clearly visible.

These connections could also be made by studying several paper maps, or, more likely, creating your own map – either actual or mental – from written information. That task would take a great deal more time, however, and the results would probably be a lot less obvious. The point of using GIS technology is to create a picture of the situation quickly and accurately, and then to be able to manipulate that picture in different ways.

In this case, for example, if you wanted to go farther, you could add other layers to what you have. Sources of drinking water might give valuable information; wind patterns might be helpful as well.  (You might not want to superimpose all of these on one another, because the resulting map could end up as a puddle of unidentifiable color. Combining two or three layers into one, and then comparing that with another is one possibility; another is simply viewing only two or three layers at a time, but in a number of combinations in order to see the relationships among them.)

Although GIS can be a great help in identifying patterns and relationships, it won’t do your thinking for you. The more creative you are, the better you understand your community, the more people you involve in analysis, the more history and context you are aware of, the more useful and accurate your analysis will be.

Looking at our medical condition example again, you might notice that we haven’t asked whether there are other areas occupied by the same ethnic group where the condition is not common, or whether other ethnic groups who live in the same relationship as this one to industrial plants seem to avoid similar medical problems. If either of these situations holds, then the question becomes “What, if anything, is unique about this group at this place?”  You have to respond not only to what you see, but also to what you don’t see to make full use of your GIS-generated information.

An important rule when analyzing GIS maps is to keep an open mind. You may believe you know the answers to your questions before you start, but don’t assume that whatever the maps show confirms your belief. Even if your initial impression is that you were right, do some digging: you may strike gold, in the form of a new insight, or another interpretation of what the map shows. Again, notice what you don’t see.

GIS can be a great tool for assessing community needs and assets, for setting or influencing policy, for planning an initiative or intervention, and for evaluating and refocusing your work. It is only a tool, however, and it’s only as accurate as the data it works with, and only as smart as the people who use it.

Use your map analysis to assist and improve your work and your community.

Doing a GIS analysis won’t do you any good unless you use it for something. The information it gives you should help you in planning and implementing interventions and community programs, in adjusting and improving your work, in deciding which community trends need attention (and providing that attention), and in improving the quality of life in your community.

In Summary

GIS (Geographic Information System) capability can change the way you and others look at your work and your community.  GIS – a method of digital mapping that allows you to add and subtract information from the maps you make in order to see spatial information more clearly, and to compare various factors and to understand relationships among them – can lead to new insights about an issue or place. It can be helpful in understanding causes, in detecting potential problems, and in predicting scenarios, among other uses.

The main uses to which members of the Tool Box community are likely to put GIS are community assessment, strategic and action planning, evaluation, and advocacy or other efforts to influence policy. GIS shows you relationships in an instant that might not be apparent from a table of figures holding the same information. For that reason, it’s a powerful method of presentation, especially for policy purposes.

The effectiveness and power of a GIS system depends on the nature of the hardware and software being used, the reliability and scale of the data fed into it, and the expertise of the people who run it and interpret its results. The advent of GIS has made it possible literally to look at the community in a new way, and to use that to guide your work.

Contributor 
Phil Rabinowitz

Online Resources

CHNA.org is a free, web-based utility to assist hospitals, non-profit community-based organizations, state and local health departments, financial institutions, and engaged citizens in understanding the needs and assets of their communities. It is provided by Community Commons, which offers over 7000 GIS data layers at state, county, zip code, block group, tract, and point-levels, contextualized mapping, visualization, analytic, impact and communication tools and apps, and searchable profiles of hundreds of place-based community initiatives. CHNA.org expands on the capabilities of Community Commons, offering not only comprehensive GIS mapping, but also analytic and reporting tools to facilitate the assessment of community health needs and assets that are critical to shaping and investing in the health and well-being of our communities.

National Spatial Database. GIS data on various issues from the Center for Advanced Spatial Technology (CAST) at the University of Arkansas.

The U.S. Census. An enormous amount of information, as well as TIGER maps and products.

Introduction to Data Analysis Using Geographic Information Systems,” by Daniel L. Falbo, Lloyd P. Queen, and Charles R. Blinn, on the website of the University of Minnesota Extension Service.

The U.S. Fish and Wildlife Service. Environmental data.

GeoCommunity, a site offering information and free data downloads.

Geographic Information Systems. Lots of information, links, and explanations.

International Geospatial and Attribute Links. Links to data sources from all 50 states, from the University of Arkansas.

National Park Service data clearinghouse.

National Renewable Energy Laboratory. Maps of renewable energy sources in the U.S.

The U.S. Geological Survey, with its store of map data.

Software companies:

Autodesk (Map3D software)

ESRI (Arc line of GIS software)

Intergraph (GeoMedia software)

Pitney Bowes (MapInfo software)