Where signal strength is low (in the mountains or a building). When moving slowly (walking). When precise coordinates are needed (self driving vehicles). Whe

Where signal strength is low (in the mountains or a building). When moving slowly (walking). When precise coordinates are needed (self driving vehicles). When precise altitude is needed (airplanes and drones). When tracking smallish things on a person (head tracking for augmented reality). When performing certain scientific measurements (continental drift). Finally, so that when I'm sitting at a stop light my navigation doesn't freak out and suddenly think I'm moving in the opposite direction. I'm sure there are tons more.