GIS: Fusing data and geography
A tipsheet by David Poulson, associate director, Knight Center for Environmental Journalism
Download a printable version of this tipsheet
Mapping a disease
When cholera gripped London in 1854, most health authorities figured the disease was spread by noxious vapors.
But Dr. John Snow noticed that cholera deaths concentrated in homes near a particular public water pump. The British epidemiologist mapped their locations and also found relatively few deaths reported at residences near other pumps.
All of the pumps drew water from the Thames River. The difference: The deadly one drew water downstream of the sewage and filth of the city while the intakes for the other pumps were upstream.
Snow uncovered a great environmental story by marrying data to geography, a process known today as Geographic Information Systems or GIS.
Nowadays, computer-driven GIS helps journalists report stories that they couldn’t get otherwise. And perhaps no reporter can better benefit from mapping software than the one who covers the environment. The sense of place, the where of the story — its geography — is vital to an environmental journalist.
Leaking a great story
Chances are you’ve already seen GIS news stories. One of the most common identifies sexual offenders who live near schools and daycare centers. Sexual offender lists are great fodder for this kind of thing. But there are other hazards worthy of plotting on a map.
Take the location of Leaking Underground Storage Tanks, the legacy of old gas stations. Most states track the progress — or lack of progress — in cleaning up the petroleum-based chemicals at these sites.
In my state (Michigan), the threat these sites pose to groundwater has prompted restrictions on installing new petroleum tanks within 300 feet of a drinking water well. But many tanks are closer. They may have been installed before the regulations or owners may have been unaware of the restriction or oblivious to a nearby well. What’s more, water wells may have been drilled near a tank long after it was installed.
With GIS you can map water wells and identify the leaking tanks that fall within 300 feet of them. You can also identify the leakers that are within 25 feet of surface water, an area that Michigan law requires all tanks to be double-walled and monitored. Once mapped, you can export to a spreadsheet the data on just those tanks. Now you can examine the extent of contamination, the progress of cleanups and the presence of noxious compounds like MTBE at the tanks leaking in particularly sensitive areas.
That’s a pretty good story. And, as a bonus, it produces a map to illustrate it. That’s the neat thing about GIS. It lets you create a data subset based on a geographic feature while giving the graphics department a head start on an illustration.
Other ideas
Say you want to profile the pollution inputs of the area that drains into a local river. You’ve got lists of local factory discharge permits, wastewater treatment plants, storm water permits, leaking petroleum tanks, large farms and other pollution sources. Unfortunately their locations are reported by county or city-political boundaries largely irrelevant to an area defined by natural features. But if you plot them on a map, you can sort out which ones fall within the irregular boundaries of the watershed. Now you’ve got just the pollution data that directly impacts the river.
It’s not just pollution sources environment reporters find worthy of mapping. Columbus Dispatch environment reporter Spencer Hunt mapped property parcel information when he examined development threats to Darby Creek, one of Ohio’s last relatively untouched havens for rare and threatened wildlife. By looking at the ownership of parcels within the watershed, he figured out how much land was protected from development and how much was owned by developers, farmers and others.
It took traditional shoe-leather reporting to sort out developers from other owners. Land could be currently farmed and yet owned by a development corporation. But in the end, Hunt quantified how much of the watershed was primed for development and identified who bought it up.
When you use GIS, the point for reporters is not so much the map that’s produced, but the opportunity to inform their reporting. The Darby Creek ownership map never appeared in the paper, says Hunt. “It was so complex and the parcels were so tiny in comparison to the watershed, we literally would have needed two pages to make it legible.”
Yet often reporter-created GIS maps are a boon to graphics departments. For the same story, Hunt placed the watershed onto a map of regional growth predictions. He shaded the map by percentage of developed land for both 2000 and 2030, dramatically illustrating a projected 60 percent population increase for a sensitive ecosystem.
“There is no other way to give readers this kind of information and analysis without an assist from a computer,” says Hunt. “For environmental reporting, mapping is key.”
David Poulson is associate director of the Knight Center for Environmental Journalism and teaches computer-assisted reporting at Michigan State University.
