A method and
system is described where a plurality of position reference devices use short-range
wireless communication protocols to transmit positioning assistance data to nearby mobile devices, and the mobile devices use the assistance data to re-calibrate their positioning systems. In some embodiments,
mobile device includes an
accelerometer and the
accelerometer measurements are used to calculate an updated velocity of the
mobile device and an updated position of the
mobile device based on the
accelerometer measurements and previous velocity and position of the mobile device. The short-range communication methods include NFC, RFID,
Bluetooth®, short-range 802.11, Wi-Fi Direct, and
high frequency focused beams such as 60 GHz. The position reference devices are passive or active NFC tags, passive or active RFID tags, other devices that include such tags as their components,
Bluetooth®-enabled devices, 60 GHz-enabled devices, and 802.11 access points that can lower their transmit power.