A method for establishing a route for an autonomous vehicle, the method comprising determining localisation information for the vehicle with respect to a frame of reference by performing a perception process to localise the vehicle with respect to the frame of reference, determining a route for the vehicle with respect to the frame of reference and controlling the vehicle such that it follows the determined route, characterised in that the method comprises: determining localisation information for the vehicle with respect to a first frame of reference by using one or more sensors to measure values of a parameter within the vehicle's local environment, the first frame of reference being a frame of reference that is fixed with respect to a current state of the vehicle; determining localisation information for the vehicle with respect to a second frame of reference by performing a perception process to localise the vehicle with respect to the second frame of reference by receiving signals from a high-error, low-drift sensor, the second frame of reference being a frame of reference that is fixed with respect to an entity, the entity being different to the vehicle, and the vehicle being moveable with respect to the entity; establishing a route for the vehicle with respect to the second frame of reference using the localisation information for the vehicle with respect to the second frame of reference; performing a transformation of the route from the second frame of reference to the first frame of reference, thereby providing a transformed route; determining a route for the vehicle with respect to the first frame of reference using the localisation information for the vehicle with respect to the first frame of reference and the transformed route; and controlling the vehicle such that it follows the determined route; the method being performed in an environment wherein the signals received from the high-error, low-drift sensor are received at a lower frequency than the frequency with which the vehicle measures values of a parameter within the vehicle's local environment. determining localisation information for the vehicle with respect to a first frame of reference by using one or more sensors to measure values of a parameter within the vehicle's local environment, the first frame of reference being a frame of reference that is fixed with respect to a current state of the vehicle; determining localisation information for the vehicle with respect to a second frame of reference by performing a perception process to localise the vehicle with respect to the second frame of reference by receiving signals from a high-error, low-drift sensor, the second frame of reference being a frame of reference that is fixed with respect to an entity, the entity being different to the vehicle, and the vehicle being moveable with respect to the entity; establishing a route for the vehicle with respect to the second frame of reference using the localisation information for the vehicle with respect to the second frame of reference; performing a transformation of the route from the second frame of reference to the first frame of reference, thereby providing a transformed route; determining a route for the vehicle with respect to the first frame of reference using the localisation information for the vehicle with respect to the first frame of reference and the transformed route; and controlling the vehicle such that it follows the determined route; the method being performed in an environment wherein the signals received from the high-error, low-drift sensor are received at a lower frequency than the frequency with which the vehicle measures values of a parameter within the vehicle's local environment.