# US 11,029,156 B2 · Aircraft magnetic declinator system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,156 B2 - Document ID: US11029156B2 - Status: Granted - Kind: B2 - Application number: 16/215,338 - Filed: 2018-12-10 - Published: 2020-06-11 - Granted: 2021-06-08 - Earliest claimed: 2018-12-10 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: Karen Deborah Hatcher Boelter - Web page: https://patentgrep.com/patent/US11029156B2 ## CPC - G01C 21/165: {combined with non-inertial navigation instruments} - G01C 21/18: Stabilised platforms, e.g. by gyroscope - G01C 21/20: Instruments for performing navigational calculations (G01C21/24, G01C21/26 take precedence) - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) ## Abstract A method, apparatus, and system for adjusting inertial reference data. The inertial reference data is received from an inertial reference unit in an aircraft. Replacement magnetic navigation data is determined for the aircraft at a current position of the aircraft. Magnetic navigation data in the inertial reference data is replaced with the replacement magnetic navigation data for the aircraft to form adjusted inertial reference data. The adjusted inertial reference data is sent to a number of aircraft systems that use the adjusted inertial reference data during operation of the aircraft. ## Claims ### Claim 1 An inertial reference system comprising: a magnetic declinator unit, wherein the magnetic declinator unit: receives inertial reference data from an inertial reference unit in the inertial reference system in an aircraft, wherein the inertial reference data includes magnetic declination data for a current position of the aircraft; determines replacement magnetic declination data for the current position of the aircraft from data previously stored within the aircraft; replaces the magnetic declination data of the inertial reference data with the replacement magnetic declination data to form replacement magnetic navigation data for the aircraft at the current position of the aircraft; replaces magnetic navigation data in the inertial reference data with the replacement magnetic navigation data for the aircraft to form adjusted inertial reference data; and sends the adjusted inertial reference data to a number of aircraft systems that use the adjusted inertial reference data during operation of the aircraft. ### Claim 2 (depends on 1) The inertial reference system of claim 1, wherein the magnetic declinator unit is located between the inertial reference unit and an avionics data bus, wherein the magnetic declinator unit: receives data bus signals from the inertial reference unit; and decodes the data bus signals to obtain the inertial reference data, and wherein in sending the adjusted inertial reference data to the number of aircraft systems that use the adjusted inertial reference data during operation of the aircraft, the magnetic declinator unit: encodes the adjusted inertial reference data to form adjusted data bus signals; and sends the adjusted data bus signals onto the avionics data bus connected to the number of aircraft systems in the aircraft that use the adjusted inertial reference data during operation of the aircraft. ### Claim 3 (depends on 2) The inertial reference system of claim 2, wherein the avionics data bus is selected from the group consisting of an ARINC 429 data bus and a MIL-STD-1553 data bus. ### Claim 4 (depends on 1) The inertial reference system of claim 1, wherein in receiving inertial reference data from the inertial reference unit in the aircraft, the magnetic declinator unit: receives data bus signals from the inertial reference unit; and decodes the data bus signals to obtain the inertial reference data. ### Claim 5 (depends on 1) The inertial reference system of claim 1, wherein the replacement magnetic navigation data is determined using true navigation data, the current position of the aircraft, and the replacement magnetic declination data describing angle variations between a true north and a magnetic north for different locations on Earth. ### Claim 6 (depends on 5) The inertial reference system of claim 5, wherein the replacement magnetic declination data comprises at least one of a World Magnetic Model or an International Geomagnetic Reference Field model. ### Claim 7 (depends on 5) The inertial reference system of claim 5, wherein the replacement magnetic navigation data comprises a replacement magnetic heading and a replacement magnetic track and wherein the true navigation data comprises a true heading and a true track. ### Claim 8 (depends on 1) The inertial reference system of claim 1, wherein the inertial reference data comprises a current latitude, a current longitude, a true track, a true heading, a magnetic heading, and a magnetic track. ### Claim 9 (depends on 1) The inertial reference system of claim 1, wherein the magnetic declinator unit: determines whether the inertial reference data is labeled as normal operation; and when the inertial reference data is labeled as normal operation, the magnetic declinator unit includes the replacement magnetic declination data; and determines the replacement magnetic navigation data for the aircraft at the current position of the aircraft; replaces the magnetic navigation data in the inertial reference data with the replacement magnetic navigation data for the aircraft to form the adjusted inertial reference data; and sends the adjusted inertial reference data to the number of aircraft systems that use the adjusted inertial reference data during operation of the aircraft. ### Claim 10 (depends on 1) The inertial reference system of claim 1, wherein the magnetic declinator unit sends the inertial reference data as received without a change when a label of normal operation is absent for the magnetic navigation data in the inertial reference data. ### Claim 11 (depends on 1) The inertial reference system of claim 1, wherein the magnetic declinator unit comprises a housing and wherein the housing includes an input data bus interface connected to the inertial reference unit and an output data bus interface configured to connect to an avionics data bus of the number of aircraft systems. ### Claim 12 (depends on 1) The inertial reference system of claim 1, wherein the magnetic declinator unit comprises a housing and wherein the housing includes a communications interface configured to receive the replacement magnetic declination data. ### Claim 13 An aircraft magnetic declinator system comprising: an input data bus interface that is connectable to an output of an inertial reference unit in an aircraft, wherein the input data bus interface receives a complementary differential bipolar return-to-zero transmission waveform; an output data bus interface that is connectable to an avionics data bus in the aircraft; and a controller that: decodes the complementary differential bipolar return-to-zero transmission waveform to obtain inertial reference data comprising a current position of the aircraft, a true heading, a true track, a magnetic heading, and a magnetic track, wherein the magnetic heading and the magnetic track are determined using magnetic declination data for the current position of the aircraft; determines replacement magnetic declination data for the current position of the aircraft from data previously stored within the aircraft; determines a replacement magnetic heading and a replacement magnetic track using the replacement magnetic declination data for the current position of the aircraft; replaces the magnetic heading and the magnetic track with the replacement magnetic heading and the replacement magnetic track to form adjusted inertial reference data; encodes the adjusted inertial reference data to form an adjusted complementary differential bipolar return-to-zero transmission waveform; and sends the adjusted complementary differential bipolar return-to-zero transmission waveform onto the avionics data bus in the aircraft. ### Claim 14 (depends on 13) The aircraft magnetic declinator system of claim 13, wherein the inertial reference data is organized into blocks of data and the controller stores the blocks of data, wherein the controller: encodes a block of data with the replacement magnetic heading and the replacement magnetic track in place of the magnetic heading and the magnetic track in the block of data. ### Claim 15 (depends on 14) The aircraft magnetic declinator system of claim 14, wherein in encoding the inertial reference data, the controller: encodes the block of data containing the replacement magnetic heading and the replacement magnetic track to form the adjusted differential bipolar return-to-zero (BPRZ) transmission waveform. ### Claim 16 (depends on 13) The aircraft magnetic declinator system of claim 13, wherein in determining the replacement magnetic heading and the replacement magnetic track using the current position of the aircraft, the controller: determines the replacement magnetic heading and the replacement magnetic track using the true heading, the true track, the current position of the aircraft, and the replacement magnetic declination data describing angle variations between a true north and a magnetic north for locations on Earth. ### Claim 17 (depends on 16) The aircraft magnetic declinator system of claim 16, wherein the replacement magnetic declination data comprises at least one of a World Magnetic Model or an International Geomagnetic Reference Field model. ### Claim 18 (depends on 13) The aircraft magnetic declinator system of claim 13, wherein the avionics data bus is selected from the group consisting of an ARINC 429 data bus and a MIL-STD-1553 data bus. ### Claim 19 A method for adjusting inertial reference data comprising: receiving the inertial reference data from an inertial reference unit in an aircraft, wherein the inertial reference data includes magnetic declination data for a current position of the aircraft; determining replacement magnetic declination data for the current position of the aircraft from data previously stored within the aircraft; replacing the magnetic declination data of the inertial reference data with the replacement magnetic declination data to form replacement magnetic navigation data for the aircraft at the current position of the aircraft; replacing magnetic navigation data in the inertial reference data with the replacement magnetic navigation data for the aircraft to form adjusted inertial reference data; and sending the adjusted inertial reference data to a number of aircraft systems that use the adjusted inertial reference data during operation of the aircraft. ### Claim 20 (depends on 19) The method of claim 19, wherein receiving the inertial reference data from the inertial reference unit in the aircraft comprises: receiving data bus signals from the inertial reference unit; decoding the data bus signals to obtain the inertial reference data; and wherein sending the adjusted inertial reference data to the number of aircraft systems that use the adjusted inertial reference data during operation of the aircraft comprises: encoding the adjusted inertial reference data to form adjusted data bus signals; and sending the adjusted data bus signals onto an avionics data bus connected to the number of aircraft systems in the aircraft that use the adjusted inertial reference data during operation of the aircraft. ### Claim 21 (depends on 20) The method of claim 20, wherein the avionics data bus is selected from the group consisting of an ARINC 429 data bus and a MIL-STD-1553 data bus. ### Claim 22 (depends on 19) The method of claim 19, wherein the replacement magnetic navigation data is formed using a true navigation data, the current position of the aircraft, and the replacement magnetic declination data describing angle variations between a true north and a magnetic north for different locations on Earth. ### Claim 23 (depends on 22) The method of claim 22, wherein the replacement magnetic declination data comprises at least one of a World Magnetic Model or an International Geomagnetic Reference Field model. ### Claim 24 (depends on 22) The method of claim 22, wherein the replacement magnetic navigation data comprises a replacement magnetic heading and a replacement magnetic track and wherein the true navigation data comprises a true heading and a true track. ### Claim 25 (depends on 19) The method of claim 19, wherein the inertial reference data comprises a current latitude, a current longitude, a true track, a true heading, a magnetic heading, and a magnetic track. ### Claim 26 (depends on 19) The method of claim 19 further comprising: determining whether the inertial reference data is labeled as normal operation; and when the inertial reference data is labeled as normal operation, determining the replacement magnetic navigation data for the aircraft at the current position of the aircraft comprises: replacing the magnetic navigation data in the inertial reference data with the replacement magnetic navigation data for the aircraft to form the adjusted inertial reference data; and sending the adjusted inertial reference data to the number of aircraft systems that use the adjusted inertial reference data during operation of the aircraft. ### Claim 27 (depends on 19) The method of claim 19 further comprising: sending the inertial reference data as received without replacing the magnetic navigation data when a label of normal operation is absent for the magnetic navigation data in the inertial reference data.