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US3890718A Expired / Lapsed US ⏱️ 0.0 years remaining

Method for determining astronomic north by gyrocompass

Assignee: Ministry of Natural Resources and Wildlife
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Filing: 1973-07-27
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Granted: 1975-06-24
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Expires: 1993-07-27
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Abstract

Abstract A gyroscope having one degree of freedom, suspended by a filar band for oscillation about a vertical axis with its spin axis in the horizontal plane tending toward North, is modified for determination of NORTH with high accuracy by providing a projected narrow beam of light indicating swing movement relative to a reference mark in a viewing port. A group of at least two and preferably three miniature photosensors spaced less than about 1* apart are employed with electronic timing apparatus, to generate signals precisely establishing time intervals of the passage of the beam from the response center of one sensor to the response center of the adjacent sensor and the interval between out and return crossings of the outer sensor. The timing observations are utilised in computational procedures based on new mathematical models of the behaviour of the swinging elements and on physical models of the sources of anomalous displacements and times, for establishing the accurate parameters of simple harmonic motion describing the rectified swing. A set of six or more determinations on a station of known latitude is shown to determine NORTH with a mean error of the order of 1 second of arc. The automatic observation of time intervals characterizing slow crossings by a relatively broad beam having a dimension in the direction of movement which is an uncertain magnitude comparable to the breadth of the sensor, is performed by gating pulses of a first train of frequency N while the sensor output exceeds a predetermined threshold level, and gating in the interval thereafter before the sensing of the beam by the adjacent sensor a train of pulses of frequency 2N, so that the count of pulses accumulated during two transit intervals and in the intervening interval effectively yields a center-to-center timing determination.

Inventors

  • 👤 Leslie F Gregerson
  • 👤 Gordon R Symonds

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-01 06:15
CPC Classifications
G; G01; G01C; G01C19/00; G01C19/02; G01C19/34; G01C19/38; Y; Y10; Y10T; Y10T74/00; Y10T74/12; Y10T74/1229; Y10T74/1257

Claims Analysis

Total Claims: 8
Claim 1
Independent Claim 260 words
The method of determining North by gyrocompassing in which a gyrocompass having one degree of freedom has its rotor spin axis in the horizontal plane and is suspended by a filar band for oscillation about a vertical axis in the band as a torsion pendulum, which comprises: observing and recording the times of transit of the spin axis while the rotor is spinning across a fixed point located close to the Meridional plane which includes and oscillation axis, and across a pair of fixed points located approximately equiangularly distant East and West from said Meridional plane; observing and recording times of transit of the spin axis with the rotor non-spinning during a plurality of oscillatory swings across said fixed points; establishing from said timing observations a mean period Pc and a mean period Pz respectively for said spinning and nonspinning swings; establishing quasi-angular velocities omega q of a Simple Harmonic Motion: x A.sin omega qt such that: omega qc 2 pi /Pc and omega zq 2 pi /Pz establishing from said time measurements the time intervals tR and tL defined by successive transits of the spin axis across the Meridional and East pair of fixed points and across the Meridional and West pair of fixed points; establishing the apparent offset distances of the nearMeridional fixed point from the equilibrium North direction represented by the differences from the half-period times Pc/2 and Pz/2 of the mean periods of swings East and West as respective time time intervals tC and tc; establishing the apparent amplitude A of said Simple Harmonic Motion as
Claim 2
Independent Claim 260 words
The method of determining North by gyrocompassing in which a gyrocompass having one degree of freedom has its rotor spin axis in the horizontal plane and is suspended by a filar band for oscillation about a vertical axis in the band as a torsion pendulum, which comprises: observing and recording the times of transit of the spin axis while the rotor is spinning across a fixed point located close to the Meridional plane which includes and oscillation axis, and across a pair of fixed points located approximately equiangularly distant East and West from said Meridional plane; observing and recording times of transit of the spin axis with the rotor non-spinning during a plurality of oscillatory swings across said fixed points; establishing from said timing observations a mean period Pc and a mean period Pz respectively for said spinning and nonspinning swings; establishing quasi-angular velocities omega q of a Simple Harmonic Motion: x A.sin omega qt such that: omega qc 2 pi /Pc and omega zq 2 pi /Pz establishing from said time measurements the time intervals tR and tL defined by successive transits of the spin axis across the Meridional and East pair of fixed points and across the Meridional and West pair of fixed points; establishing the apparent offset distances of the nearMeridional fixed point from the equilibrium North direction represented by the differences from the half-period times Pc/2 and Pz/2 of the mean periods of swings East and West as respective time time intervals tC and tc; establishing the apparent amplitude A of said Simple Harmonic Motion as
Claim 3
Dependent Claim 23 words
The method of claim 1 wherein the timing observations are carried out with an accuracy of one millisecond of time for all intervals.
Claim 4
Dependent Claim 55 words
The method of claim 2 wherein the direction of the spin axis is represented by a light beam projected as a narrow vertical band having a width in the direction of swing of the order of 120 microns and said fixed points are realized as photosensitive spot area elements providing electrical outputs for beam crossings.
Claim 5
Dependent Claim 33 words
The method of claim 3 wherein said elements are disposed on the gyrocompass and the swing axis of the gyroscope is aligned with the vertical center of a theodolite associated with the gyrocompass.
Claim 6
Dependent Claim 35 words
The method of claim 3 wherein the gyrocompass is mounted on a theodolite having the vertical through its center aligned with the swing axis, and said elements are mounted on the telescope of the theodolite.
Claim 7
Dependent Claim 80 words
The method of claim 1 wherein the quantity k is calculated as k (4 pi 2/Pz2)/(x + Square Root x2+ y) Omega cos phi where: x ( Omega cos phi W.LPc2)/8 pi 2 y W.L.(Pc2/Pz2- 1) Omega is the angular velocity of Earth''s rotation about the polar axis; phi is the latitude of the observation W is the weight of the spinning member L is the distance from the point of suspension to the mass center of the swinging gyroscope.
Claim 8
Dependent Claim 166 words
The method of claim 1 wherein the spinning swing observtions precede the non-spinning swing observations, the spinning rotor is braked immediately following the spinning swing observations, and the non-spinning observations commence when the rotor has stopped, further comprising the steps of taking the arithmetical mean of the half-periods of swings to each side to derive Pc/2 and Pz/2; establishing the drift of the parameter D 4 pi 2/Pz2 to the instant of time of the commencement of the non-spinning swings by the rates of decrement rA, rB, ra, rb of the half-period times to the left and right respectively for spinning and non-spinning swings, establishing the angle S between the equilibrium direction of the gyroscope and the near-Meridional fixed point as S(A, B, a, b) ((2n - 1)/4 + Mu ) .r(A, B, a, b) + period arithmetical mean, where n is the number of swings considered for the side, Mu is the proportional time of braking and is equal to zero for non-spinning swing observations.

References Cited (Backward Citations)

US3577646A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1978-06-23 1978-12-23 1979-06-24 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1982-06-23 1982-12-23 1983-06-24 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1986-06-23 1986-12-23 1987-06-24 $7700.00 Window Closed / Lapsed

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