Indoors positioning and navigation systems and methods are described herein. In one embodiment, a system for inspecting or maintaining a storage tank includes a vehicle having: at least one sensor for determining properties of a storage tank and a navigation system. The navigation system includes an acoustic transmitter carried by the vehicle and an inertial measurement unit (IMU) sensor configured to at least partially determine a location of the vehicle with respect to the storage tank. The vehicle also includes a propulsion unit configured to move the vehicle within the storage tank, and an acoustic receiver fixed with respect to the storage tank. The vehicle moves inside the storage tank in concentric arcs with respect to the acoustic receiver.