Method, apparatus and computer program for azimuth determination e.g. for autonomous navigation applications
First Claim
1. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
- analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, anddetermining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises the sub-steps of;
acquiring said first and second azimuth data over a plurality of sampling periods within a time window,performing a statistical analysis on said first and second azimuth data for said sampling periods, andidentifying a magnetic field disturbance on the basis of said statistical analysis, andwherein said azimuth determining step comprises basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of;
i) said second azimuth data without reference to the first azimuth data, orii) a combination of said second azimuth data and said first azimuth data.
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Accused Products
Abstract
For an observer equipped with a first azimuth data source responsive to a magnetic field to deliver first azimuth data, such as a compass, and with a second azimuth data source delivering second azimuth data and which is independent of magnetic fields, such as a gyroscope. The azimuth is determined by:
- analyzing the first and second azimuth data to determine whether a magnetic disturbance is present, and
- determining azimuth selectively on the basis of: the first azimuth data, the second azimuth data, or a combination of the first and second azimuth data, as a function of the result of the comparing step.
In an embodiment, the choices of azimuth data source and events such as magnetic disturbances, sensor updates, types of trajectory deduced, are stored as a history sequence over successive time windows, by analogy with a DNA sequence, and is exploited for optimizing azimuth or navigation results.
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Citations
90 Claims
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1. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises the sub-steps of;acquiring said first and second azimuth data over a plurality of sampling periods within a time window, performing a statistical analysis on said first and second azimuth data for said sampling periods, and identifying a magnetic field disturbance on the basis of said statistical analysis, and wherein said azimuth determining step comprises basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of; i) said second azimuth data without reference to the first azimuth data, or ii) a combination of said second azimuth data and said first azimuth data. - View Dependent Claims (2, 3)
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4. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises the sub-steps of;acquiring said first and second azimuth data over a plurality of sampling periods within a time window, determining the normal standard deviation of said first azimuth data and the normal standard deviation of said second azimuth data for said sampling periods, determining the ratio of said normal standard deviation of said first azimuth data to said normal standard deviation of said second azimuth data for said sampling periods, comparing said ratio to a determined threshold value, and identifying a magnetic field disturbance in a situation in which said ratio crosses said determined threshold, wherein said azimuth determining step comprises basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of; i) said second azimuth data without reference to the first azimuth data, or ii) a combination of said second azimuth data and said first azimuth data. - View Dependent Claims (5, 6)
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7. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data,said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises the sub-steps of; acquiring said first and second azimuth data over a plurality of sampling periods within a determined time window, for a succession of time windows, performing an analysis on first and second azimuth data for said sampling periods of at least a current time window and its preceding time window, taking at least one of the following actions on the basis of said analysis; i) using only said first azimuth data of a current window to determine said azimuth, ii) using only said second azimuth data of a current window to determine said azimuth, iii) using a combination of said first azimuth data and said second azimuth of a current time window to determine said azimuth, iv) identifying a type path currently followed, and v) updating at least one parameter of said second azimuth data source. - View Dependent Claims (8, 9)
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10. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises the sub-steps of;acquiring said first and second azimuth data for a succession of time windows, for at least some time windows of said succession, recording events occurring within a said time window, to obtain a sequence history of azimuth events over successive time windows, and using said sequence history as input to optimize the determination of said azimuth and/or a determination of a position and/or a trajectory. - View Dependent Claims (11, 12)
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13. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises the sub-steps of;acquiring said first and second azimuth data for a succession of time windows, for at least some time windows of said succession, recording events occurring within a said time window, said events comprising at least one of; i) choice of source(s) of azimuth data used for determining azimuth data, ii) sensor update or recalibration, iii) identified trajectory type, iv) presence of a magnetic field disturbance, to obtain a sequence history of azimuth events over successive time windows, and using said sequence history as input to optimize the determination of said azimuth and/or a determination of a position and/or a trajectory. - View Dependent Claims (14, 15)
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16. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises acquiring said first and second azimuth data over a plurality of sampling periods within a determined time window, and performing said acquisition for a succession of time windows. - View Dependent Claims (17, 18)
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19. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data,said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step further comprises the steps of; acquiring said first and second azimuth data over a plurality of sampling periods within a time window, analyzing said first and second azimuth data of that time window, on the basis of said analysis, performing at least one of i) updating or recomputing at least one azimuth data of said time window, and ii) updating or recomputing a present real-time azimuth. - View Dependent Claims (20, 21)
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22. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data,said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, wherein said analyzing step comprises the sub-steps of; acquiring said first and second azimuth data over a plurality of sampling periods within a time window, determining a position on the basis of said data, analyzing said first and second azimuth data of that time window, on the basis of said analyzing step, performing at least one of; i) recomputing at least one determined position in said time window, and ii) updating or recomputing a present real-time position. - View Dependent Claims (23, 24)
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25. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, further comprising the steps of;determining, on the basis of said analyzing step, a first condition in which no substantial magnetic field is present, enabling an update of said second azimuth data source, on the basis of said first azimuth data from said first azimuth data source, only if said first condition is satisfied. - View Dependent Claims (26, 27)
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28. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, further comprising the steps of;determining a current trajectory in terms of an amount of change in azimuth, using said determined current trajectory as a parameter for commanding a management of said first and/or second azimuth data source(s) and/or as a parameter for said analyzing step and/or said determining step. - View Dependent Claims (29, 30)
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31. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, further comprising the steps of;determining a current trajectory in terms of an amount of change in azimuth, identifying a current trajectory following a specific change of direction, notably a 90°
or 180°
change of direction,using said identified specific change of direction as a parameter for commanding a management of said first and/or second azimuth data source(s) and/or as a parameter for said analyzing step and/or said determining step. - View Dependent Claims (32, 33)
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34. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, further comprising the steps of;determining a current trajectory in terms of an amount of change in azimuth, identifying a current trajectory following a substantially straight line direction, corresponding to substantially no change in azimuth using said identified substantially straight line direction as a parameter for commanding a management of said first and/or second azimuth data source(s) and/or as a parameter for said analyzing step and/or said determining step. - View Dependent Claims (35, 36)
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37. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, further comprising the steps of;performing said azimuth determination over at least two successive determined time windows, for each successive time window, determining whether a trajectory follows a substantially straight line direction, determining whether a trajectory for a current time window and for a previous time window both follow a substantially straight line direction, in the affirmative, using trajectory data of said previous window and said current window to establish a continuity relation in which said trajectory is considered to follow a same substantially straight line. - View Dependent Claims (38, 39)
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40. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, further comprising the steps of;producing a history sequence of past events up to a current time, said history sequence expressing at least a magnetic field characteristic determined over a respective time window, said magnetic field characteristic being classed as one of; i) a magnetically stable environment, ii) a magnetically disturbed environment, iii) a potentially magnetically disturbed environment, and wherein said azimuth determining step comprises using at least one said determined magnetic field characteristic as a parameter to determine said azimuth. - View Dependent Claims (41, 42)
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43. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independent of magnetic field, second azimuth data comprising the steps of:
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analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, based on the determination of said analyzing step, further comprising the steps of;producing a history sequence of past events up to a current time, said history sequence expressing at least an azimuth or trajectory characteristic determined over a respective time window, said azimuth or trajectory characteristic being classed as one of; i) a displacement substantially along a straight line, ii) a displacement along a curve with a significant substantial continuous change in azimuth, iii) a general situation not corresponding to listed situations i) or ii), and wherein said determining step comprises using at least one said determined azimuth or trajectory characteristic as a parameter to determine said azimuth. - View Dependent Claims (44, 45)
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46. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, wherein said analyzing means comprises;means for acquiring said first and second azimuth data over a plurality of sampling periods within a time window, means for performing a statistical analysis on said first and second azimuth data for said sampling periods, and means for identifying a magnetic field disturbance on the basis of said statistical analysis, and wherein said azimuth determining means comprises means for basing the determined azimuth on one of; i) said second azimuth data alone, or ii) a combination of said second azimuth data and said first azimuth data, when a magnetic disturbance is identified. - View Dependent Claims (47, 48)
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49. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, wherein said analyzing means comprises;means for acquiring said first and second azimuth data over a plurality of sampling windows within a time window, means for determining the normal standard deviation of said first azimuth data and the normal standard deviation of said second azimuth data for said sampling periods, means for determining the ratio of said normal standard deviation of said first azimuth data to the normal standard deviation of said second azimuth data for said sampling periods, means for comparing said ratio to a determined threshold value, and means for identifying a magnetic field disturbance when said ratio crosses said determined threshold, and wherein said azimuth determining means comprises means for basing the determined azimuth on one of; i) said second azimuth data alone, or ii) a combination of said second azimuth data and said first azimuth data, when a magnetic disturbance is identified. - View Dependent Claims (50, 51)
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52. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, where said analyzing means comprises;means for acquiring said first and second azimuth data over a plurality of sampling periods within a determined time window, and for performing said acquisition for a succession of time windows, means for performing an analysis on first and second azimuth data for said sampling periods of at least a current time window and its preceding time window, means for taking at least one of the following actions on the basis of said analysis; i) using only said first azimuth data of a current window to determine said azimuth, ii) using only said second azimuth data of a current window to determine said azimuth, iii) using a combination of said first azimuth data and said second azimuth of a current time window to determine said azimuth, iv) identifying a type path currently followed, and v) updating at least one parameter of said second azimuth data source. - View Dependent Claims (53, 54)
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55. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, wherein said analyzing means comprises;means for acquiring said first and second azimuth data for a succession of time windows, means for recording events occurring within a said time window, for at least some time windows of said succession, to obtain a sequence history of azimuth events over successive time windows, and means for receiving said sequence history as input to optimize a determination of said azimuth and/or a determination of a position and/or a trajectory. - View Dependent Claims (56, 57)
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58. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, wherein said analyzing means comprises;means for acquiring said first and second azimuth data for a succession of time windows, means for recording events occurring within a said time window, for at least some time windows of said succession, said events comprising at least one of; i) choice of source(s) of azimuth data used for determining azimuth data, ii) sensor update or recalibration, iii) identified trajectory type, iv) presence of a magnetic field disturbance, to obtain a sequence history of azimuth events over successive time windows, and means for receiving said sequence history as input to optimize a determination of said azimuth and/or a determination of a position and/or a trajectory. - View Dependent Claims (59, 60, 63)
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61. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, wherein said analyzing means comprises means for acquiring first and second azimuth data samples at successive time intervals within a determined time window, and for performing said acquisition for a succession of time windows. - View Dependent Claims (62)
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64. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, wherein said analyzing means further comprises;means for acquiring said first and second azimuth data over a plurality of sampling periods within a time window, means for analyzing said first and second azimuth data of that time window, and means, cooperating with said analyzing means, for performing at least one of; i) updating or recomputing at least one azimuth data of said time window, and ii) updating or recomputing a present real-time azimuth. - View Dependent Claims (65, 66)
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67. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, wherein said analyzing means further comprises;means for acquiring said first and second azimuth data over a plurality of sampling periods within a time window, means for determining a position on the basis of said data, means for analyzing said first and second azimuth data of that time window, means, cooperating with said analyzing means, for performing at least one of; i) recomputing at least one said determined position in said time window, and ii) updating or recomputing a present real-time position. - View Dependent Claims (68, 69)
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70. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, further comprising;means for determining, on the basis of analysis data from said analyzing means, a first condition in which no substantial magnetic disturbance is present, and means for enabling an update of said second azimuth data source, on the basis of said first azimuth data from said first azimuth data source, only if said first condition is satisfied. - View Dependent Claims (71, 72)
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73. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, further comprising;means for determining a current trajectory in terms of an amount of change in azimuth, means for commanding a management of said first and/or second azimuth data source(s) and/or said analyzing means and/or said determining means on the basis of said determined current trajectory as a parameter for determining an azimuth. - View Dependent Claims (74, 75)
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76. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, further comprising;means for determining a current trajectory in terms of an amount of change in azimuth, means for identifying a current trajectory following a specific change of direction, notably a 90°
or 180°
change of direction,means for commanding a management of said first and/or second azimuth data source(s) and/or said analyzing means and/or said determining means on the basis of said specific change of direction. - View Dependent Claims (77, 78)
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79. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, further comprising;means for determining a current trajectory in terms of an amount of change in azimuth, means for identifying a current trajectory following a substantially straight line direction, corresponding to substantially no change in azimuth, means for commanding a management of said first and/or second azimuth data source(s) and/or said analyzing means and/or said determining means on the basis of said identified substantially straight line direction. - View Dependent Claims (80, 81)
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82. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, further comprising;means for performing said azimuth determination over at least two successive determined time windows, means, operative for each successive time window, for determining whether a trajectory follows a substantially straight line direction, means for determining whether a trajectory for a current time window and for a previous time window both follow a substantially straight line direction, and, in the affirmative, operative for using trajectory data of said previous window and said current window to establish a continuity relation in which said trajectory is considered to follow a same substantially straight line. - View Dependent Claims (83, 84)
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85. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, further comprising;means for producing a history sequence of past events up to a current time, said history sequence expressing at least a magnetic field characteristic determined over a respective time window, said magnetic field characteristic being classed as one of; i) a magnetically stable environment, ii) a magnetically disturbed environment, iii) a potentially magnetically disturbed environment, and wherein said azimuth determining means comprises means using at least one said determined magnetic field characteristic as a parameter to determine said azimuth. - View Dependent Claims (86, 87)
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88. An apparatus for determining an azimuth, said apparatus comprising:
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a first azimuth data source responsive to a magnetic field to deliver first azimuth data, a second azimuth data source delivering second azimuth data independent of magnetic field, means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and means for determining said azimuth selectively on the basis of;
said firstazimuth data, said second azimuth data, or a combination of said first and second azimuth data based on the determination of an analysis by said analyzing means, further comprising; means for producing a history sequence of past events up to a current time, said history sequence expressing at least an azimuth or trajectory characteristic determined over a respective time window, said azimuth or trajectory characteristic being classed as one of; i) a displacement substantially along a straight line, ii) a displacement along a curve with a significant substantial continuous change in azimuth, iii) a general situation not corresponding to listed situations i) or ii), and wherein said determining means comprises using at least one said determined azimuth or trajectory characteristic as a parameter to determine said azimuth. - View Dependent Claims (89, 90)
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Specification