Further inaccuracies may be caused by the type of wave the receiver records. In case of just ground wave reception a constant is included in the calculation if the distance is permanent. In case of just space wave reception the reception side cannot influence the time fluctuations. Time fluctuations are influenced directly by the changing altitude of the reflecting and bending layer of the ionosphere. Similar problems arise where ground and skywaves overlap. This field is not constant but changes in the course of the day between approximately from the transmitter position.