Tracks in the sand tell the story of where and how a robot travels. The ninety-degree pivot in this photo consumes more power than the straight driving. The amount of turning, called 'steering activity', is determined by the presence of obstacles that the robot must circumvent versus obstacles that it can surmount. If a robot can surmount all obstacles in a terrain, then routes are straight lines to objectives. If a robot must circumvent most obstacles, then paths are circuitous. Details of terrain obstacles cannot be known a priori, so rover locomotion is capable of going over most obstacles, and rover navigation avoids the rest.