Hydrographic surveying without a tide gauge

Depth in hydrographic surveys is measured from the water surface during the survey operation. However, the water surface of oceans, seas and lakes moves as a result of meteorological, oceanographic and tidal effects. Depth values measured at any time and water level should be reduced to a specific vertical datum in order to be used at a different time and different water level. To accomplish that, the changes in water level must be determined. Traditionally, many different types of tide gauges are used for this purpose. The aim of this study is to establish the connection of depth values to a vertical datum without using a tide gauge. For this purpose, an algorithm based on the GPS carrier phase measurement is introduced here. The result shows that, the height of each point at the sea bottom may be obtained without using a tide gauge via the proposed method. Furthermore, if this method is performed, important error sources such as heave, surge, and tides, which affect the sounding, can be eliminated.