Indoor location position system and method

A location position system, comprising:

• a plurality of beacons arranged in a location area, the plurality of beacons being arranged in a grid formation divided into a plurality of sub-grids;
• and
• a mobile computing device implementing a location position application, the mobile computing device comprising:
• at least one microphone configured to receive audio signals in a frequency range of 16 kHz and above to 24 kHz,
• at least one antenna configured to receive radio signals,
• one or more processors coupled to the at least one microphone and the at least one antenna and configured to receive the audio signals and the radio signals, and
• a non-transitory computer-readable storage medium having a plurality of instructions stored thereon, which, when executed by the one or more processors, cause the one or more processors to perform operations comprising:
• receiving a radio signal from a particular beacon of the plurality of beacons, the radio signal comprising a data component uniquely identifying the particular beacon;
• identifying a particular sub-grid of the plurality of sub-grids in the grid formation based on the received radio signal, the particular sub-grid being associated with a set of sub-grid beacons of the plurality of beacons;
• receiving an audio signal from each of the set of sub-grid beacons, each audio signal:
• (i) having a frequency in the frequency range of 16 kHz to 24 kHz and a transmission delay from a reference time, (ii) lacking any additional identifying data, and (iii) being separately transmitted from the radio signal transmitted by the particular beacon;
• and
• determining a position of the mobile computing device based on the received audio signals,
• wherein:
• identifying the particular sub-grid of the plurality of sub-grids in the grid formation is further based on grid formation setup data, the grid formation setup data being sufficient to identify:
• (i) the grid formation, and (ii) which sub-grid beacon of the set of sub-grid beacons corresponds to a received audio signal;
• the grid formation setup data includes line-of-sight compensation data;
• and
• determining the position of the mobile computing device based on the received audio signals comprises:
• determining an initial position estimate based on the received audio signals;
• determining whether line-of-sight compensation is appropriate based on the initial position and the line-of-sight compensation data;
• and
• when line-of-sight compensation is appropriate, adjusting a time of arrival for at least one of the received audio signals to obtain one or more time adjusted audio signals, wherein determining the position of the mobile computing device is based on the received one or more time adjusted audio signals.