# US 2021/0333409 A1 · Systems and methods for inertial measurement unit aided detection and exclusion against spoofing attacks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0333409 A1 - Document ID: US20210333409A1 - Status: Published application - Kind: A1 - Application number: 16/858,250 - Filed: 2020-04-24 - Published: 2021-10-28 - Earliest claimed: 2020-04-24 - Assignees: Honeywell International Inc. - Applicants: Honeywell International Inc. - Inventors: Xiao Cao; Ping Ye; Brian Schipper - Web page: https://patentgrep.com/patent/US20210333409A1 ## CPC - G01S 19/215: {issues related to spoofing} - G01S 19/20: Integrity monitoring, fault detection or fault isolation of space segment - G01S 19/393: {Trajectory determination or predictive tracking, e.g. Kalman filtering} - G01S 19/40: Correcting position, velocity or attitude - G01S 19/47: the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial - G01S 19/49: whereby the further system is an inertial position system, e.g. loosely-coupled - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract Techniques for detecting and excluding spoofed Global Navigation Satellite System (GNSS) signals are described. Using position data acquired from inertial sensors, a line of sight (LOS) estimation can be determined to various satellites. This data can be compared with range data provided by a GNSS receiver, for example, by subtracting the LOS estimations with corresponding GNSS ranges. The difference can then be compared to an appropriate threshold to determine whether GNSS spoofing is present. Additionally, the non-spoofed GNSS signals can be used to generate an updated position solution, which is verified by an integrity algorithm. If verified, the updated position solution can be used to calculate the position of the vehicle. However, if not verified, the disclosed techniques can adjust the thresholds used to determine GNSS spoofing and perform additional iterations of integrity monitoring to acquire a verified positioning solution. ## Claims ### Claim 1 A system, comprising: a processor; an inertial measurement unit (IMU) coupled to the processor, wherein the IMU is configured to: acquire a series of dynamic measurements for a vehicle corresponding to a time period, and transmit the series of dynamic measurements to the processor; a Global Navigation Satellite System (GNSS) receiver coupled to the processor, wherein the GNSS receiver is configured to: receive GNSS data for the vehicle comprising satellite ephemeris data and range data corresponding to the time period, transmit the GNSS position data to the processor; and a reference clock coupled to the GNSS receiver and the processor, wherein the reference clock is configured to synchronize the time period with a reference time period; wherein the processor is configured to: calculate navigation reckoning based on the series of dynamic measurements, determine at least one line of sight (LOS) range based on the navigation reckoning and satellite ephemeris data, wherein the at least one LOS range is determined between one satellite of one or more satellites and the vehicle, compare each of the at least one LOS range with range data from the GNSS receiver to acquire at least one error differential value, compare the at least one error differential value to a threshold value, wherein the threshold value is indicative of GNSS spoofing with respect to the respective satellite of the one or more satellite; eliminate one or more spoofed GNSS satellites whose error differential value is beyond the threshold value; verify GNSS satellite measurements with an autonomous integrity algorithm, if the GNSS satellite measurements are not verified, then adjust the threshold value; and reset related GNSS satellites tracking channels in the GNSS receiver. ### Claim 2 (depends on 1) The system of claim 1, wherein to verify GNSS satellite measurements further comprises using an autonomous receiver integrity monitoring algorithm (RAIM). ### Claim 3 (depends on 1) The system of claim 1, wherein to verify GNSS satellite measurements further comprises to: generate at least one GNSS satellite data set based on each of the GNSS satellite measurements whose corresponding error differential value is less than the threshold value; filter the at least one GNSS satellite data set; generate at least one GNSS position solution based on the filtering; and verify the at least one GNSS position solution using an autonomous integrity algorithm. ### Claim 4 (depends on 3) The system of claim 3, wherein to filter the at least one GNSS satellite data set further comprises to filter using a least squared algorithm or a Kalman filter. ### Claim 5 (depends on 1) The system of claim 1, wherein the processor is further configured to determine a position of the vehicle based on the verified GNSS satellite measurements. ### Claim 6 (depends on 1) The system of claim 1, wherein the range data comprises at least one of carrier phase, pseudorange, and psuedorange rate data. ### Claim 7 (depends on 1) The system of claim 1, wherein the at least one error differential value is determined by the absolute value of a difference between the at least one LOS range and a respective pseudorange corresponding to one satellite of the one or more satellites. ### Claim 8 A non-transitory computer-readable medium having computer-executable instructions stored thereon which, when executed by one or more processors, cause the one or more processors to: receive a series of dynamic measurements and Global Satellite Navigation System (GNSS) position data of a vehicle corresponding to a time period, wherein the GNSS position data comprises satellite ephemeris data and range data; calculate navigation reckoning based on the series of dynamic measurements; determine at least one line of sight (LOS) range based on the navigation reckoning and satellite ephemeris data, wherein the at least one LOS range is determined between one satellite of one or more satellites and the vehicle; compare each of the at least one LOS range with GNSS range data to acquire at least one error differential value; compare the at least one error differential value to a threshold value, wherein the threshold value is indicative of GNSS spoofing with respect to the respective satellite of the one or more satellites; eliminate one or more spoofed GNSS satellites whose error differential value is beyond the threshold value; verify GNSS satellite measurements with an autonomous integrity algorithm, if the GNSS satellite measurements are not verified, then adjust the threshold value; and reset related GNSS satellite tracking channels in the GNSS receiver. ### Claim 9 (depends on 8) The non-transitory computer-readable medium of claim 8, wherein the computer-executable instructions further cause the one or more processors to synchronize the time period with a reference time period. ### Claim 10 (depends on 8) The non-transitory computer-readable medium of claim 8, wherein to verify GNSS satellite measurements further comprises using an autonomous receiver integrity monitoring algorithm (RAIM). ### Claim 11 (depends on 8) The non-transitory computer-readable medium of claim 8, wherein the computer-executable instructions further cause the one or more processors to: generate at least one GNSS satellite data set based on each of the GNSS satellite measurements whose corresponding error differential value is less than the threshold value; filter the at least one GNSS satellite data set; generate at least one GNSS position solution based on the filtering; and verify the at least one GNSS position solution using an autonomous integrity algorithm. ### Claim 12 (depends on 11) The non-transitory computer-readable medium of claim 11, wherein to filter the at least one GNSS satellite data set further comprises to filter using a least squared algorithm or a Kalman filter. ### Claim 13 (depends on 8) The non-transitory computer-readable medium of claim 8, wherein the computer-executable instructions further cause the one or more processors to determine a position of the vehicle based on the verified GNSS satellite measurements. ### Claim 14 (depends on 8) The non-transitory computer-readable medium of claim 8, wherein the at least one error differential value is determined by the absolute value of a difference between the at least one LOS range and a respective pseudorange corresponding to one satellite of the one or more satellites. ### Claim 15 A method, comprising: acquiring a series of dynamic measurements and Global Satellite Navigation System (GNSS) position data of a vehicle corresponding to a time period, wherein the GNSS position data comprises satellite ephemeris data and range data; calculating navigation reckoning based on the series of dynamic measurements; determining at least one line of sight (LOS) range based on the navigation reckoning and satellite ephemeris data, wherein the at least one LOS range is determined between one satellite of one or more satellites and the vehicle; comparing each of the at least one LOS range with GNSS range data to acquire at least one error differential value; comparing the at least one error differential value to a threshold value, wherein the threshold value is indicative of GNSS spoofing with respect to the respective satellite of the one or more satellites; eliminating one or more spoofed GNSS satellites whose error differential value is beyond the threshold value; verifying GNSS satellite measurements with an autonomous integrity algorithm, if the GNSS satellite measurements are not verified, then adjusting the threshold value; and resetting related GNSS satellite tracking channels in the GNSS receiver. ### Claim 16 (depends on 15) The method of claim 15, further comprising synchronizing the time period with a reference time period. ### Claim 17 (depends on 15) The method of claim 15, wherein the at least one error differential value is determined by the absolute value of a difference between the at least one LOS range and a respective pseudorange corresponding to one satellite of the one or more satellites. ### Claim 18 (depends on 15) The method of claim 15, further comprising: generating at least one GNSS satellite data set based on each of the GNSS satellite measurements whose corresponding error differential value is less than the threshold value; filtering the at least one GNSS satellite data set; generating at least one GNSS position solution based on the filtering; and verifying the at least one GNSS position solution using an autonomous integrity algorithm. ### Claim 19 (depends on 18) The method of claim 18, wherein filtering the at least one GNSS satellite data set further comprises using a least squared algorithm or a Kalman filter. ### Claim 20 (depends on 15) The method of claim 15, further comprising determining a position of a vehicle based on the verified GNSS satellite measurements.