Navigation aids are tools used to help people find their way. POLARIS, also known as the North Star, is a bright star in the northern sky that can be used to determine direction. LORAN is a navigation system that uses low frequency radio signals to determine position. SONAR is a system that uses sound waves to detect objects underwater. RADAR is a system that uses radio waves to detect objects in the air or on the ground. A GYROSCOPE is a device that uses the Earth's gravity to measure orientation. A sextant is an instrument used to measure the angle between two visible objects. Maps are visual representations of an area that can be used to determine location. An autopilot is a system that can control a vehicle without human input. GPS is a satellite-based navigation system. A roadmap is a MAP that shows the route from one place to another. A POLESTAR is a star that is used to determine direction.