Transfer of heights to islands in West-Estonian Archipelago using hydrodynamic levelling

During the last decade sea level measurements by means of pressure sensors have become wide-spread, since they are compact, can withstand icy conditions, are easy to integrate with data loggers and communication systems. This study uses two years (2010-2011) long sea level series collected by pressure gauges for hydrodynamic levelling. As a result, the accuracy of hydrodynamic levelling was estimated to be ±1.5 cm in West-Estonian Archipelago. Therefore the height differences calculated from sea level series of contemporary pressure gauges were used as reference for historic staff gauge readings with data sampling 12 h and for some days sea level observations in calm weather and ice covered sea conditions. The comparisons indicated that the height transfer accuracy ±1.5 cm with different observation periods and data samplings is guaranteed only up to 20 km distances. Over longer distances the frequent data sampling and at least one year sea level observations must be carried out for geodetic applications.