Consumer GPS changed the world. Knowing one's location and the ability to locate objects enabled whole fields of technologies. Yet there is no effective system for accurate indoor localization.

Most state-of-the-art indoor localization systems provide semantic localization, answering "Where Am I?" by telling the user what room or area of a room they are in. We aim to provide true localization, in practice this amounts to order 1 decimeter accuracy in 3D-space.

To achieve this, we exploit the rolling shutter of the CMOS imager in modern smartphones. By modulating (blinking) LED lights at high frequency (1-7 kHz) each light appears solidly on to any people in the room while communicating data to any smartphone in the room.