  Landmark-based navigation systems have proven benefits relative to
traditional turn-by-turn systems that use street names and distances. However,
one obstacle to the implementation of landmark-based navigation systems is the
complex challenge of selecting salient local landmarks at each decision point
for each user. In this paper, we present Pharos, a novel system that extends
turn-by-turn navigation instructions using a single global landmark (e.g. the
Eiffel Tower, the Burj Khalifa, municipal TV towers) rather than multiple,
hard-to-select local landmarks. We first show that our approach is feasible in
a large number of cities around the world through the use of computer vision to
select global landmarks. We then present the results of a study demonstrating
that by including global landmarks in navigation instructions, users navigate
more confidently and build a more accurate mental map of the navigated area
than using turn-by-turn instructions.
