Article via The Verge – By Russell Brandom: “The past month’s Rim Fire blazed through more than a quarter million acres of land in California, but the tensest moment came on August 27th, when the fire came close to threatening San Francisco’s water supply. If the blaze had advanced any closer than it did, it would start dumping ash into reservoirs, spurring a potential public health crisis. Stopping the fire required the forestry equivalent of a goal line stand, dropping three DC-10s worth of retardant in an attempt to push back the blaze. The planes were easy to assemble, but the larger problem was knowing where to drop the payload. According to Russ Johnson, disaster response chief for a mapping company called Esri, firefighters usually target fires as they cross ridges, allowing the retardant will flow downhill and cover more ground. But the threat to the water supply had forced their hand. The fire had to be stopped on a relatively flat plane, and even minor changes in slope would make an immense difference in the payload’s effect on the fire. Suddenly, firefighters needed detailed meter-to-meter elevation data on a patch of land that no one had cared about just hours before. “You have very little room for error,” Johnson says, “and the consequences can be really devastating.” Fortunately, they found the information they needed, pulled from government survey data and routed through Esri’s servers. The payload was dropped, together with brush-clearing bulldozers and efforts from thousands of firefighters, and the fire turned back. It’s a sign of how crucial mapping technology has become in modern disaster response. FEMA still takes the lead providing relief, but a new breed of mapping companies has sprung up to make that relief smarter and more directed, manipulating geographic information systems (GIS) to show responders where their help is needed most. Simply corralling publicly available data can be the difference between containing a fire and watching it slip out of control.”