| Many different chart datum, including Lowest Possible Low Water, Indian Spring Low Water, Chart Datum on British Admiralty Charts and Theoretical Depth Datum, have been adopted in marine charting in the Yangtze Estuary during past centuries due to historical reasons. The discrepancy of different chart datum to some extent hinders scientific research and engineering application, so it's necessary to figure out the relationships of the chart datum and study the conversion methods.To solve the problems mentioned above, firstly we selected 17 hydrological stations as sample and calculate their values of different chart datum. And then different continuous curved surfaces were derived by using the spatial interpolation method, so different chart datum adopted in the Yangtze Estuary have been simulated.Furthermore, we designed a program, which can rapidly execute the conversion among these different chart datum based on ArcGIS Engine components. The software consists of two main parts. The first one is to calculate the values of different chart datum, and the second is to conduct the spatial interpolation, chart datum simulation, and the conversion of different chart datum.Lastly we applied our method to measure the area of tidal flat in Yangtze Estuary. When we calculate the area of tidal flats, which are based on different chart datum, we can get different results. It was proved when we studied on the tidal flats in Shanghai during past years. In this research, the conversion result is introduced to calculate the area of the tidal flat in Shanghai, and it shows that:based on the Theoretical Bathymetrical Datum, areas of the tidal flats above-5m and-2m isobaths are respectively 2722.12km2and 1399.28 km. And based on the Wusong Datum, the areas above the same isobaths are respectively 2351.39km2 and 1005.73 km2. The statistics show that there are respectively 13.6% and 28.1% discrepancies due to the application of different chart datum.
|
PDF Full Text Request