A bat navigational aid is a tool used by bats to help them navigate in the dark. ECHO (4 letters) is a type of sound wave that can be used to detect objects in the environment. Sonar (5 letters) is a type of sound wave that is used to measure the distance and direction of objects underwater. LORAN (5 letters) is a type of radio navigation system that uses low frequency radio signals to determine position. Sextant (7 letters) is an instrument used to measure the angle between two objects in the sky, such as stars or planets. RADAR (5 letters) is a type of electromagnetic wave that is used to detect objects in the environment. MAP (3 letters) is a representation of an area, usually on a flat surface. CHART (5 letters) is a graphical representation of data, such as a MAP or graph. All of these tools are used by bats to help them navigate in the dark.