Dig a trench about 8 inches deep that follows the full length and width of your future path. Fill it with 7 inches of gravel, smooth it out, tamp it down, and top it with a 1-inch layer of sand.

It then looks for this color and texture in the rest of the video image. If a smooth "road" extends about ... allows the robot to find the best path from point to point, even as it avoids obstacles.