In 2002 the Environmental Agency of the Republic of Slovenia started with the modernisation of the tide gauge station in Koper, which was first set lip in 1958. Besides the recording of mean sea level and sea water temperature, the modern tide gauge station will also provide precise meteorological data (wind speed and direction, air pressure. air temperature and humidity) and uninterrupted monitoring at the permanent GPS station. This makes it possible to permanently monitor the position of the GPS antenna reference determine the position of the reference point of the tide gauge station, and it allows us 10 connect the monitoring of the sea level with the terrestrial reference system.. The paper presents the geodetic activities at the tide gauge station Koper in the trial period, carried out in order to monitor the local horizontal and vertical stabilities of the GPS antenna reference point of the permanent GPS station in the frame of the terrestrial micro network.