Abstract

Abstract. 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 and GPS devices; a 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 multiquadric RBF (radio basis function), and the best geostatistical method was ordinary cokriging. The root mean square error in both methods measured less than 0.3 m. The quality of the interpolation methods was analysed in two 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 m 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.

Highlights

  • Bathymetric surveying has undergone many conceptual changes in the last few decades, especially since the mid 20th century due to the availability of the single-beam echo sounder

  • The last phase of digital terrain modelling refers to the application of a model (Weibel and Heller, 1991; Hutchinson and Gallant, 2000; Hengl et al, 2003; Oksanen, 2006), this research visualized the annual water level oscillation

  • A scenario was made for the northwestern Jasen inundation area, outside the Nature Park (Fig. 11)

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Summary

Introduction

Bathymetric surveying has undergone many conceptual changes in the last few decades, especially since the mid 20th century due to the availability of the single-beam echo sounder. The main goal of most such hydrographic surveys is to gain data necessary to develop nautical charts featuring special details of types of navigational hazards. Other goals include gaining information crucial to the management and protection of coastal areas, exploitation of resources, national spatial data infrastructure and tourism purposes. The success of bathymetric measurement depends mostly on a detailed planning process, which in turn enables the organization and tracking of the measurement process from start to finish (IHO, 2005). During this particular research, the measurement plan included a wide range of activities and was performed in several phases according to the standards of the International Hydrographic Organization.

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