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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: to compare the efficiency of 16 different interpolation methods, to discover the most appropriate interpolators for the development of a raster model, to calculate the surface area and volume of Lake Vrana, and to compare the differences in calculations between separate raster models. The best deterministic method of interpolation was ROF multi-quadratic, and the best geostatistical, ordinary cokriging. The mean quadratic error in both methods measured less than 0.3 m. 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 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. [ABSTRACT FROM AUTHOR]

With regard to its geographical position, role and significance,North-Western Croatia represents the key area of the Republic of Croatia. It is the area of a long-lasting continuity of population and a great, although regionally differentiated, agrarian density. A long and intensive pressure on the environment is one of the most important factors which have influenced the ecological soil depth. Because of the presumed influence of the quantitative geomorphological features (average height, relative height, slope length, length and relative height index, inclination, surface regularity, expositions) and lithology features (rock strength coefficient)on the volume and intensity of slope processes, a multiple regression analysis has been carried out for the dependent variable of ecological depth and the quoted variables as independent assessors. [ABSTRACT FROM AUTHOR]