Disclosed is determining GNSS satellite position visibility by possessing an orbital segment representing the transit of a satellite in orbit over time, a coarse ray angle interval, a fine ray angle interval, and a digital surface model. Disclosed is propagating coarse ray at coarse ray angle intervals increments in a first pass between an observable point and orbital segment at a respective coarse ray angle to determine whether the coarse ray is obstructed by features of the DSM, and recording a status of the coarse ray based on whether the coarse ray was obstructed. If pairs of successive coarse rays have different status, designating the coarse ray with NLOS visibility, then performing a second pass by propagating, per each designated coarse ray, fine rays at fine ray angle intervals, and saving an indication of time at which LOS visibility to the satellite is obstructed.

Disclosed is a method of detecting and rejecting a spoofing or jamming signal source by receiving at a first device a forecast of a visibility for each Global Navigation Satellite System (GNSS) satellite signal source in the forecast at a GNSS receiver coupled to the first device, calculating from at least an elevation and the received visibility of the satellite signal sources in the forecast a predicted Signal to Noise Ratio (SNR), comparing SNR acquired by the GNSS receiver of one or more of the satellite signal sources to the predicted SNR, detecting a spoofing signal source based on acquiring a higher SNR than predicted or a jamming signal source based on acquiring a lower SNR than predicted, and rejecting the spoofing or jamming signal source based on differences between the acquired and predicted SNR.

Systems and methods are provided for monitoring or protecting an electric power distribution system using protective devices that may rely on accurate time signals from a common time source. A first protective device may receive a first time signal deriving from the common time source and a second protective device may receive a second time signal deriving from the common time source. The first time signal and the second time signal may be compared; when a difference between them exceeds a defined threshold, time signal manipulation may be detected. The protective devices may modify their operation in response to or to account for the time signal manipulation.

An embodiment of the present application discloses a global navigation satellite system (GNSS) integrated circuit (IC). The GNSS IC includes a GNSS module, a memory and a processor. The GNSS module is arranged operably to receive a to-be-identified broadcast GNSS signal. The memory is arranged operably to store a plurality of ephemeris aiding data candidates, wherein the ephemeris aiding data candidates are not provided by the GNSS module. The processor is arranged operably to determine whether the to-be-identified broadcast GNSS signal is a spoofing signal based on an ephemeris aiding data reference in the ephemeris aiding data candidates.

A receiver authenticates a wideband (WB) signal from global navigation satellites (GNSS) using a narrowband (NB) signal that is also transmitted from the satellites. The NB signal includes segments that are transmitted in time and frequency slots of successive transmission frames. The NB signal is less susceptible to a smart WB jammer. Also, the NB signal segments may also be transmitted at a relative power level with respect to the WB signal, where the relative power level may vary in a known pattern so as to distinguish the WB signal of the satellite from a stronger WB signal from a smart jammer.

A method, system and product for identifying fabricated maritime signals. The method comprises obtaining one or more location-reporting signals of a maritime vessel, wherein the one or more location-reporting signals comprise one or more respective sets of geographical coordinates, each of which having a timestamp; determining that the one or more location-reporting signals are at least partially fabricated, wherein said determining is based on an identification that a maritime path indicated by the one or more location-reporting signals is unfeasible; and performing a responsive action.

A method, system and product for identifying spoofed maritime signals based on receiving reception stations. The method comprises obtaining one or more location-reporting signals of a maritime vessel, wherein the one or more location-reporting signals comprise one or more respective sets of geographical coordinates, each of which having a timestamp. The method further comprises determining that the one or more location-reporting signals are at least partially fabricated. The determination comprises: identifying a station that received the one or more location-reporting signals, wherein the station having a reception polygon; and determining that at least one set of geographical coordinates indicated by the one or more location-reporting signals is fabricated based on the reception polygon of the station. The method further comprises performing a responsive action.

A method, system and product for dead reckoning-based analysis of fabricated maritime data. The method comprises determining an initial location of the maritime vessel; determining speed and heading information using the location-reporting signals; computing estimated location of the maritime vessel at a specific time, based on the initial location and based on the speed and heading information; comparing the estimated location with a reported location at the time according to location-reporting signals; based on the comparison, determining that the location-reporting signals are at least partially fabricated; and in response to the determination that the location-reporting signals are at least partially fabricated, performing a responsive action.

Examples in accordance with this disclosure provide a system for detecting a spoofed signal, the spoofed signal comprising position-navigation-timing (PNT) data. The system can include a first antenna and a second antenna, both configured to receive one or more first signals from one or more navigation satellites. The first antenna and second antenna can be configured to be separated by a first distance. The system can include a first receiver coupled to the first antenna and a second receiver coupled to the second antenna, where each antenna is configured to receive one or more signals from the respective antenna. Each of the first receiver and the second receiver are configured to extract a respective carrier phase data.

A method for detecting a decoy source of a satellite radionavigation signal, the method being executed by a satellite radionavigation signal reception device comprising two receivers, the method comprising the steps of: for each signal received by the reception device and transmitted by a different satellite, estimating the phase of the signal received by each receiver, computing the estimated phase difference for each receiver, comparing the phase differences computed for multiple different satellites and, if at least two phase differences computed for two different satellites are substantially identical, concluding that a decoy source is present.