Tidal correction using GPS : determination of the chart datum
Ellmer, Wilfried & Patrick Goffinet
Tidal corrections in Germany are normally made using the "Wasserstandserrechnungskarte" (tidal correction chart), which is similar to the co-tidal co-range chart, and tide gauge measurement data. This method may produce major errors under unfavourable weather conditions. The precision and reliability of tide corrections can be improved considerably by using PDGPS for height measurements. This method is independent of tide gauge readings and does not require a conversion of actual water levels at the tide gauge to the survey location. However, GPS measurements relate heights to an ellipsoid, according to the reference service used. They do not provide data relative to the chart datum, which is the information that is crucial to chart users. This paper deals with a project of Bundesamt ffr Seeschifffahrt und Hydrographie, the Federal Maritime and Hydrographic Agency of Germany (BSH). The result of the project is a seamless chart datum surface referred to the ETRF89 ellipsoid, which is the same ellipsoid that is used by the German Satellitenpositionierungsdienst SAPOS. The surface is computed by using the results of numerical hydrodynamic models and a tide gauge levelling campaign.
Event: XXIII International FIG Congress : Shaping the change
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