Method and system for harmonising an angular positioner reference in relation to an Earth-based reference frame

The method involves obtaining data (E20) representing intensity measured by a local gravity measuring device and/or representing rotation speed of an Earth. An angular positioner is fixed during a period of obtaining the data representing intensity and/or rotation speed of the Earth by measuring (E10) inertial information on a period of operation. An angular bias affecting reference of the positioner is evaluated (E30) from the obtained data. The reference of the positioner is harmonized (E40) from terrestrial reference by compensating the evaluated angular bias. Independent claims are also included for the following: (1) a system for harmonizing an angular positioner reference in relation to an Earth-based reference frame (2) a computer program comprising a set of instructions for implementing a method for harmonizing an angular positioner reference in relation to an Earth-based reference frame (3) a recording medium comprising a set of instructions for implementing a method for harmonizing an angular positioner reference in relation to an Earth-based reference frame.