Amazon.com, Inc.
System to determine portable device presence at a portal

Abstract:

A portable device comprises a magnetometer for detecting a magnetic field. When the portable device is at or near a portal, the portable device may detect data from the portal, such as beacon data or a connection message. Responsive to the data from the portal, the portable device operates the magnetometer to detect and characterize a magnetic field generated by the portal, such as by characterizing the magnitude, polarity, and direction of the magnetic field. The portable device generates magnetometer data to indicate the magnetic field strength detected by the magnetometer. The magnetometer data is then transmitted to the portal, along with a device identifier. The portal compares the received magnetometer data to expected magnetic field data to determine presence of the portable device at the portal. The portable device is associated with an account, providing information about entry of a user of that account entering the portal.