Using the web and mobile devices, we now have comprehensive maps of the great outdoors, our planet and its mountains, plains and oceans. But what about the places where GPS does not work, such as underground, in buildings and megastructures, under dense tree canopies, on board ships or inside aircraft? Research cartographer Keith Clarke is working toward mapping the great indoors using new technologies. See what that entails and what it enables. Series: "GRIT Talks" [Science] [Show ID: 31421]