This method, implemented in a mounted information display device, which incorporates a main sensor and an inertial sensor, and which determines the positioning by a hybrid inertial method including determining a calculated position by a main method using data acquired by the main sensor and determining a succession of estimated positions using the calculated position and data acquired by the inertial sensor, includes: obtaining at a first calculation time instant T1 a first estimated position of the device at a reference time instant, calculated by the hybrid inertia method; obtaining at a second time instant T2 a second estimated position of the device at the same reference time instant, calculated by the main method; comparing a difference between the first and second positions and a tolerance threshold; and, if the difference is less than the threshold, validating the positioning calculation by the hybrid inertial method, otherwise raising an alert.