engleski

A comparison of interpolation methods on the basis of data obtained from a bathymetric survey of Lake Vrana, Croatia

The bathymetric survey of Lake Vrana included a wide range of activities that were performed in several different stages, in accordance with the standards set by the International Hydrographic Organization. The survey was conducted using an integrated measuring system which consisted of three main parts: a single- beam sonar Hydrostar 4300, GPS devices Ashtech Promark 500 – base, and a Thales Z-Max – rover. A total of 12 851 points were gathered. In order to find continuous surfaces necessary for analysing the morphology of the bed of Lake Vrana, it was necessary to approximate values in certain areas that were not directly measured, by using an appropriate interpolation method. The main aims of this research were as follows: a) to compare the efficiency of 14 different interpolation methods and discover the most appropriate interpolators for the development of a raster model ; b) to calculate the surface area and volume of Lake Vrana, and c) to compare the differences in calculations between separate raster models. The best deterministic method of interpolation was RBF multiquadratic, and the best geostatistical ordinary cokriging. The mean quadratic error in both methods measured less than 0.3 metres. The quality of the interpolation methods was analysed in 2 phases. The first phase used only points gathered by bathymetric measurement, while the second phase also included points gathered by photogrammetric restitution. The first bathymetric map of Lake Vrana in Croatia was produced, as well as scenarios of minimum and maximum water levels. The calculation also included the percentage of flooded areas and cadastre plots in the case of a 2-metre increase in the water level. The research presented new scientific and methodological data related to the bathymetric features, surface area and volume of Lake Vrana.

bathymetric survey; single beam sonar; interpolation methods; RTK-GPS; Lake Vrana

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