Hero drones. Thousands of hikers get lost in the woods each year. To find them, rescuers fan out across the words, searching for the proverbial needle in a haystack. MIT researchers, though, came up with a way to use drones. Not just one or two (not uncommon is search and rescue operations), but essentially a radar-based, vision system mesh of, say, a dozen drones that can build a forest map without GPS and use it to ensure they cover all of it in the search for lost hikers. There are limits, but it’s a promising development and proof that drones are good for more than just annoying your neighbors.