GPS only works outdoors.  For indoor navigation, an accurate and low-cost positioning system is still needed.  AltVision has invented a new materials approach for indoor positioning.  The ceilings, walls, and floors can be coated with different patterns using invisible materials.  These patterns can be detected by tiny low-cost sensors that can be integrated into smart-phones, head-mount displays, smart-glasses, and other electronic systems.  The invisible patterns serve as "indoor satellites" that, through trilateration, can be used to determine the sensors' positions within millimeter accuracy.  This positional tracking technology can be used for different applications, including way-finding in stores, virtual reality (VR), augmented reality (AR), robot and drone navigation.