| CPC G01S 19/215 (2013.01) [G01S 19/05 (2013.01)] | 20 Claims |
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1. A method for detecting spoofing in a Global Navigation Satellite System (GNSS), the method comprising:
receiving signals at a GNSS receiver that purport to be from satellites in the GNSS;
processing the signals to determine a calculated position of the GNSS receiver;
searching a list of distance measuring equipment transponders (DME transponders) around the calculated position to select a set of DME transponders for testing an integrity of the signals received by the GNSS receiver;
sorting the set of DME transponders in order based on a respective distance between the calculated position and a respective position of each of the DME transponders in the set of DME transponders;
selecting a subset of the DME transponders from the set of DME transponders based on the sorting;
for each DME transponder in the subset of the DME transponders, autotuning to a frequency corresponding to a frequency of the DME transponder;
determining a real slant range from the DME transponder;
sampling and filtering a power level of a received signal from the DME transponder for a period;
calculating an expected slant range based on a height, position, and known location of the DME transponder;
comparing the real slant range with the expected slant range to produce a difference, and
when the difference exceeds a first threshold, incrementing a counter,
when the counter exceeds a second threshold, indicating that the position is spoofed and broadcasting an indication to vehicles or ground stations.
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