Method of aligning an axisymmetric vibrating sensor inertial navigation system and corresponding inertial navigation system

1. A method of aligning an inertial unit fitted to a carrier, the inertial unit having an axially symmetrical vibrating sensor that generates a vibration, wherein the method includes the step of exciting the sensor with a control signal that determines the position of the vibration for which the sensor presents drift error variation that is minimized relative to the drift en or variations for other positions of the vibration, and the step of defining an initial geographical orientation of the inertial unit, the method being performed while the carrier is immobile.

2. The method according to claim 1 , including a calibration stage comprising the steps of exciting the sensor to control vibration in successive mutually-different positions and at mutually-different temperatures, and for each vibration position, of measuring variations in drift error as a function of temperature, and of selecting a position for which variations in drift error are the smallest.

3. The method according to claim 1 , including a calibration stage comprising the step of exciting the sensor to cause vibration to take place in successive mutually-different positions at constant temperature, and for each position, of measuring variations in drift error at mutually-different instants, and of selecting a position for which the variations in drift error are the smallest.

4. The method according to claim 1 , including a calibration stage comprising the steps of exciting the sensor to cause it to vibrate in successive mutually-different positions at mutually-different temperatures, of measuring, in each vibration position, variations in the drift error as a function of temperature, of selecting positions for which the variations in drift error are the smallest, in measuring, for those positions, the variations in drift error at mutually-different instants, and in selecting a position for which the variations in drift error as a function of the instants are the smallest.

5. The method according to claim 1 , including a calibration stage comprising the steps of modeling the drift errors and of determining a drift error correction.

6. An inertial unit fitted to a carrier, comprising an axially symmetrical vibrating sensor, and means for exciting the sensor to generate vibration, wherein the inertial unit further comprises means for establishing vibration in a position for which the sensor presents variation in drift error that is the smallest compared with variation in drift error for other positions of the vibration, an initial geographical orientation being defined by said position when the carrier is immobile.

7. The inertial unit according to claim 6 , including a memory member for storing the position in which the sensor presents drift error having the smallest variations.

8. The inertial unit according to claim 7 , including memory means for storing a model of drift error and means for producing a drift error correction.

9. A method of navigating a carrier on which an inertial unit is fitted, said inertial unit having an axially symmetrical vibrating sensor that generates a vibration, wherein the method includes the step of establishing the position of the vibration for which the sensor presents drift error variation that is minimized relative to the drift error variations for other positions of the vibration, defining while the carrier is immobile an initial geographical orientation of the inertial unit from said established position of the vibration and while the carrier is mobile, using the initial geographical orientation as a reference for calculating an instantaneous geographical orientation and a position of the carrier.