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, 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. 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.
The objects of this study are the hillslopes in the broader area of Duvanjsko polje (Bosnia and Herzegovina). Slopes can be defined as relief surfaces determined by geographical position, slope inclination (related with horizontal surface), aspect, and degree of curvature (profile and planar).Recent slope shapes can be defined as results of series of natural and anthropogenic factors during relief genesis and evolution. It is possible to correlate slope characteristics with geological structure and other natural geographic features (climate, soils, vegetation etc.) using geomorphometrical analysis. The main aims of this study are: a) analysis of morphometric relief indicators, b) analysis of relationships between morphometric indicators, structural and lithological features, and c) synthesis of all analyzed indicators in order to better understand exogeomorphological and morphostructural features of the investigated area. The final intention is to assess the extent and intensity of the dominant geomorphologic processes. Special attention was given to the detailed geomorphometrical analysis of morphostructures in the broader area of Duvanjsko polje in GIS environment based on DMR. The applied geomorphometrical relief analysis included the use of different methods for precise calculation of the investigated area’s numerical relief parameters, which enabled a mutual comparison of specified parameters and comparison with tectonic units and lithology maps. The aim of this approach is a more exact analysis and interpretation of morphometric relief parameters as indicators of the investigated area’s endogenous and exogenous processes’ characteristics.
Original scientific paper The aim of this research is to choose the most appropriate interpolators for the purpose of geomorphologic research, by comparing 7 deterministic methods. For the purpose of developing a model and comparing interpolators, the research used a set of elevation data gathered by aero-photogrammetry and stereo-restitution. The accuracy of interpolation methods was tested by analysing 8 statistic parameters, which were obtained by methods of crossvalidation, split sampling and jackknifing. Apart from analysing the parameters, the research also compared the interpolation methods by visual means, through graphic representation of data (two-dimensional and three-dimensional) on the basis of credible graphic representations of sets of data. The research also tested the effect of power, number of neighbours, distance and sectors on the quality of output data. The multiquadratic radial basis function (MQ-RBF) proved to be the best deterministic method of interpolation by all the relevant parameters.Keywords: digital terrain model; deterministic interpolation methods; methods of comparison of interpolation methods; root mean square error; Vrana Lake Nature Park Točnost determinističkih metoda interpolacije u generiranju digitalnog modela reljefa -primjer PP Vransko jezeroIzvorni znanstveni članak Cilj istraživanja je, usporedbom 7 determinističkih metoda interpolacije, odabrati najprikladnije interpolatore za potrebe geomorfoloških istraživanja. Za izradu modela i usporedbu metoda interpolacije korišten je skup visinskih podataka prikupljenih aerofotogrametrijskom izmjerom i stereorestitucijskom obradom. Točnost metoda interpolacije ispitana je analizom 8 statističkih parametara koji su dobiveni metodama unakrsnog vrednovanja, podijeljenih uzoraka i ponovno uzorkovanje (jackknifing). Osim analize parametara, interpolacijske metode su uspoređene i vizualno, kroz grafički prikaz podataka (dvodimenzionalno i trodimenzionalno) na osnovi vjerodostojnih grafičkih prikaza skupa podataka. Ispitan je utjecaj eksponenta udaljenosti, broja susjeda, udaljenosti i sektora na izlazne rezultate. Utvrđeno je da je multikvadratna radijalna osnovna funkcija (MK-ROF) po svim parametrima najbolja deterministička metoda interpolacije.Ključne riječi: digitalni model reljefa; determinističke metode interpolacije; metode usporedbe metoda interpolacije; PP Vransko jezero; srednja kvadratna pogreška
The peak areas of the Velebit mountain range display an interesting periglacial geomorphology. The appearance of forms is the result of the interdependent geological, geomorphologic, climatic, vegetational and pedological characteristics of the area. The structural and lithological properties of the rock complex, and the inclination of the slope, play a signifi cant role in periglacial relief modelling. Climatic elements are also important, as they infl uence the intensity and duration of the processes. Low temperatures and relatively high precipitation during the last ice age (Würm III), served to intensify the activity of periglacial processes and relief modelling of the entire Velebit area. Nivation and cryofraction are the predominant periglacial processes which are represented by snow avalanches and stone streams. Air temperatures and soil temperatures (at 30, 60, 90 cm depth) were measured, presented and reviewed, together with other attributes and the slope inclination of the area. The interactions between ground temperature, snow cover and wind patterns play important roles in frost action. In addition to slope inclination, the penetration of warm winds (jugo) and warming of snow on the NE slopes are also important factors in destabilizing the snow cover and triggering avalanches. Snow avalanches are most intensive on slopes with declinations from 35° up to 50°, especially on the parts without vegetation cover.
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