"Turn Left" Versus "Walk Towards the Café": When Relative Directions Work Better Than Landmarks

An automatic mechanism that gives verbal navigation instructions to pedestrians in situ needs to take into account a number of factors. Besides giving the instruction at the right time and place, the information needs to be as unambiguous as possible for the user to both choose the correct path and be confident in doing so. Humans make extensive use of landmarks when describing the way to others and are more successful following instructions that include landmarks. We present a study comparing landmark-based instructions with relative direction instructions on pedestrians in a real city environment, measuring both objective and subjective success. We find that at some decision points, relative direction instructions work better. We present a method that uses openly available geographic data to predict which kind of instruction is preferable at a given decision point.