Attached to that computer is a rake that, when commanded, drops into the sand to trace a design. When programmed beforehand and performing autonomously, it keeps track of its position with four white poles staked into the shore that also define how large the drawing should be.
The lead Disney researcher said he wanted "to build an artist robot that could keep creating new artwork." Right now the Beachbot is best at curved lines and most drawings now are done in an area ten meters square, but it can do right angles with the help of its laser scanner and inertial sensor, and it can draw thin and thick lines with seven individually-controlled tines on its rake.
Ultimately, they want to get up to drawings that are a kilometer long, and after that, make sand designs that rival the Nazca Lines. We think the Beachbot is swell, but we'd rather do that with a Land Rover Defender. Go ahead and prepare your old-fogey indignation the first time you see a kid on the beach with one of these, though: "You know, when I was a kid and wanted to draw in the sand..."