Method for designing a navigation path and method for orienting a sighting member from said navigation path

A method of performing a navigation calculation on the basis of a hybrid inertial navigation system on board a vehicle, the navigation system being arranged to perform a hybrid first navigation calculation using a Kalman filter that receives inertial navigation data and non-inertial navigation data, the method being characterized in that it comprises the steps of:

• using the hybrid inertial navigation system to perform an inertial second navigation calculation on the basis of the inertial navigation data;
• calculating in real time a difference between the first navigation calculation and the second navigation calculation, and subjecting the difference to lowpass filtering having a convergence time longer than a period of the Kalman filter and shorter than the Schuler period;
• and
• using the filtered difference to correct the second navigation calculation.