engleski

Differential Sea Level Measurement : Solution for Croatian Islands Height Datum

In the Croatian part of the Adriatic Sea, there are 698 islands, 389 islets and 78 reefs, which make the Croatian archipelago the largest in the Adriatic Sea and second largest in the Mediterranean Sea (after the Greek’ s). Only 47 of the 698 islands are inhabited. The local economy is relatively underdeveloped, though strong expansion of tourism in the last decade stimulates it. Stronger economy growth with new infrastructural projects demands better definition of geodetic datum. Most of islands have never been unified under the same official height datum. In the course of new official geodetic datum introduction, expansion of height network on larger islands is planned. Problem of outer islands height datum definition arises. In this paper differential sea level measurement is proposed as first approximate solution. Systematic measurements of sea level in the Adriatic Sea began in 1859 in Trieste. It is interesting that the old official height datum, which is still in use, is defined as the mean sea level at tide gauge Trieste in 1875. Since this first step more than 40 tide gauge stations have been placed at the eastern part of the Adriatic Sea. These efforts had two purposes: to scientifically research the tide and to fulfil practical demands of the hydrographic survey (safety of navigation). An impressive database of sea level data measured along the east coast of the Adriatic Sea has been a base for numerous scientific researches. Sea level data of five tide gauges along eastern Adriatic Sea coast, on which new height datum is constrained, were analysed. Their time stability, differences between differential sea level measurements and geometric levelling, values of mean sea level and different geoid models fit are given. As a conclusion, usage of historical sea level data on some outer islands and new sea level measurements with sufficient time span for this purpose are suggested.

height datum; tide gauge; differential sea level

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