A method includes: acquiring, from a store terminal via a network, limited product information indicating a limited product for which a time available for sale in one branch store corresponding to the store terminal is limited; acquiring, from a communication terminal of a user via the network, i) a request for a purchase menu of affiliated stores and ii) a branch store identifier (ID) specifying one branch store corresponding to a device ID specifying a beacon signal transmitter disposed in the one branch store; generating, based on the limited product information, the request for the purchase menu, and the branch store ID, privileged purchase menu information corresponding to the one branch store; and outputting the privileged purchase menu information to the communication terminal.

A modular backpack system includes a personal floatation harness having an automatic inflator mechanism and pack attachment features; and a plurality of pack modules selectively attachable to the pack attachment features to form a floatation-enhanced backpack. Each one of the plurality of pack modules may further include a different arrangement for accommodating accessories. For example, the different arrangements may include arrangements having different compartments. Other arrangements may have different attachment features. The different attachment features may include different lash points. The backpack module may be one taken from the list of: a pack adapted for kayaking with a waterproof compartment and lash points for ready access to accessories; a pack adapted for sailing with waterproof and non-waterproof compartments; a pack adapted for hiking with multiple compartments for tools and supplies; and a pack adapted for everyday carry (EDC) having multiple quick-access compartments for carrying everyday tools.

A beacon transmitter device (BTD.sub.1; 700; 900) is disclosed. The beacon transmitter device comprises a controller (710; 910) and a short-range wireless beacon transmitter (732; 932). The controller is configured to cause a first transmission (S12) of a short-range wireless beacon signal (BA.sub.1) by the beacon transmitter, the beacon signal identifying a beacon region. The controller is also configured to wait during a beacon delay time period (BDTP), and then cause a second transmission (S32) of the short-range wireless beacon signal (BA.sub.1) by the beacon transmitter. The beacon delay time period (BDTP) is sufficiently long to allow a short-range wireless beacon receiver device (P.sub.1), when being in a passive mode, being in range of the beacon region and having received the first transmission of the beacon signal, to receive and react (S34) on the second transmission of the beacon signal.

Determining a vertical location of a hand-held computing device. At least some of the example embodiments are computer-implemented methods including: generating an estimate of expected vertical location based on items of beacon data received from beacons by a radio receiver of the hand-held computing device, generating an error covariance of the estimate of expected vertical location based on the items of beacon data, calculating a level normalized change based on measurements of barometric pressure by a pressure sensor of the hand-held computing device, calculating the vertical location of the hand-held computing device based on the level normalized change, the error covariance of the estimate of expected vertical location, and the estimate of expected vertical location, and activating a relevant map for a level comprising the vertical location and displaying the vertical location on a display device of the hand-held computing device.

User devices (1-4) are each provided with a data connection (20) to a remote server (30) and a beacon transceiver. Device (2) is operable to actively transmit beacon signals including its unique beacon identification code for a limited period. During active transmissions by device (2), devices (1 & 3) are within range of the transmissions and are operable to extract the beacon identification code of the transmitting device (2) and thus directly infer that they are in proximity to the transmitting device (2). The receiving devices (1, 3) communicate with server (30) their own unique beacon identification code and the received beacon identification code of the transmitting device (2). In response, the server (30) communicates details of the transmitting device (2) to the receiving devices (1, 3) and the beacon identification codes of the receiving devices (1, 3) to the transmitting device (2). The transmitting device (2) is thus able to infer the proximity of the receiving devices (1, 3) without the receiving devices (1, 3) having to transmit any beacon signals.

Systems and methods for navigating an aerial vehicle are provided. One example aspect of the present disclosure is directed to a method for navigating an aircraft. The method includes receiving, by one or more processors, one or more first geographic coordinates via an interface configured to receive geographic coordinates from a satellite transmission. The method includes receiving, by the one or more processors, one or more second geographic coordinates via an interface configured to receive geographic coordinates from a ground transmission. The method includes determining, by the one or more processors, that the one or more first geographic coordinates and the one or more second geographic coordinates are inconsistent. The method includes updating, by the one or more processors, a flight plan using the one or more second geographic coordinates when the one or more first geographic coordinates are inconsistent with the one or more second geographic coordinates.

The subject matter described herein includes methods and systems for performing physical measurements using radio frequency (RF) signals. According to one embodiment of the present invention, a method is disclosed for determining the distance between a first radio device and a second radio device. The method includes transmitting a radio frequency (RF) signal from the first radio device and receiving the RF signal by the second radio device. The method further includes a determining a carrier frequency of the RF signal and determining a slope of a carrier phase versus the carrier frequency corresponding to a rate of change of the carrier phase with the carrier frequency. The method also includes determining a physical distance between the first radio device and the second radio device based on the slope; wherein the physical distance is proportional to the slope plus an integer ambiguity term and a bias term.

Positioning, navigation, and timing (PNT) signals, such as those used in GNSS or LORAN systems, may be vulnerable to spoofing attacks. To generate trustworthy time and location data at a receiver, one must at least reduce the likelihood of or be capable of detecting spoofing attacks. Embodiments of the present invention, as presented herein, provide solutions for detecting spoofing of PNT signals. Various aspects incorporated into the described embodiments which assist in detecting spoofing attacks may include but are not limited to: monitoring the SNR of received PNT signals of a first modality and switching over to an alternate PNT modality when an anomaly is detected, comparing data associated with signals of multiple PNT modalities to identify a discrepancy indicative of spoofing on one of the multiple PNT modalities, and implementing a security regime to prevent spoofers from being able to produce perceivably authentic, but corrupt, replica signals of a PNT modality.

Positioning, navigation, and timing (PNT) signals, such as those used in GNSS or LORAN systems, may be vulnerable to spoofing attacks. To generate trustworthy time and location data at a receiver, one must at least reduce the likelihood of or be capable of detecting spoofing attacks. Embodiments of the present invention, as presented herein, provide solutions for detecting spoofing of PNT signals. Various aspects incorporated into the described embodiments which assist in detecting spoofing attacks may include but are not limited to: monitoring the SNR of received PNT signals of a first modality and switching over to an alternate PNT modality when an anomaly is detected, comparing data associated with signals of multiple PNT modalities to identify a discrepancy indicative of spoofing on one of the multiple PNT modalities, and implementing a security regime to prevent spoofers from being able to produce perceivably authentic, but corrupt, replica signals of a PNT modality.

A distance measuring device according to an embodiment includes a first device including a first transceiver configured to transmit a first known signal and a second known signal and receive a third known signal corresponding to the first known signal and a fourth known signal corresponding to the second known signal, a second device including a second transceiver configured to transmit the third known signal and the fourth known signal and receive the first and second known signals and a calculating section configured to calculate a distance between the first device and the second device on a basis of phases of the first to fourth known signals, and the first transceiver and the second transceiver transmit/receive the first and third known signals one time each and transmit/receive the second and fourth known signals one time each, performing transmission/reception a total of four times.