They mention facts like this: The city of Kathmandu was already well mapped before the earthquake, but, in the past week, volunteers have tripled the amount of mapping data in Nepal in OpenStreetMap.

And all this matters. The maps that HOT makes “improve outcomes,” in the lingo of international relief organizations. In other words, they enable rescuers to deliver food, shelter, and supplies to areas that need them most. It is almost certain that they greatly help reduce suffering, and it is very likely that they save lives.

But to really understand why this activation has worked better, it’s good to return to the rain clouds. Volunteers need pictures of Nepal from above so they can then trace them. Tracing works exactly as it sounds: People sitting at their computers see a road on an underlying image file and click-and-drag a digital version of that road on top of it. Once complete, they add that road to an online database called OpenStreetMap (OSM), where it can be calculated with like data or printed out as a map. (OSM is free to use and can be edited by anyone: It’s the Wikipedia of world maps.)

But tracing requires pictures of the ground, and pictures require satellites.

One of the world’s highest-resolution private satellites is called WorldView-3. The American company that owns it, DigitalGlobe, supplies imagery to many governments, including the United States.

Because of the thunderstorms, WorldView-3 couldn’t get a clear view of Nepal as it passed over the country on April 26. But later, orbiting above Bangladesh and about to cross the Indian Ocean, the satellite tilted backward and could see Kathmandu through the clouds. It snapped a picture.

“If you stand up, bend over, and look between your legs behind you, that’s what the satellite did,” said Kevin Bullock, a product specialist at the company.

It was the first picture of earthquake-wrecked Nepal. DigitalGlobe also open-licensed the imagery that night. By Sunday evening in North America, volunteers were already beginning to integrate the information into OSM. Since then, many major satellite providers—including DigitalGlobe; Google’s satellite company, Skybox; the California-based startup Planet Labs; and the large European contractor Astrium—have released imagery of the affected area.

This is both a victory of technology and a victory of organization. The last time there was a major natural disaster and accompanying HOT activation, imagery was captured but could not be used on the ground for some time. Companies were not prepared to license their data openly. “With Haiyan, it took several days,” says Bullock. “It wasn’t fast enough.”

Dale Kunce, a geographic information specialist with the American Red Cross, said that HOT, imagery providers, mapping companies and the U.S. State Department’s Humanitarian Information Unit were all much better organized and familiar with each other than they had been 18 months ago.