Department of Geography

The solar radiation model r.sun is a flexible and efficient tool for the estimation of solar radiation for clear-sky and overcast atmospheric conditions. In contrast to other models, r.sun considers all relevant input parameters as spatially distributed entities to enable computations for large areas with complex terrain. Conceptually the model is based on equations published in the European Solar Radiation Atlas (ESRA). The r.sun model was applied to estimate the solar potential for photovoltaic systems in Central and Eastern Europe. The overcast radiation was computed from clear-sky values and a clear-sky index. The raster map of the clear-sky index was computed using a multivariate interpolation method to account for terrain effects, with interpolation parameters optimized using a cross-validation technique. The incorporation of terrain data improved the radiation estimates in terms of the model's predictive error and the spatial pattern of the model outputs. Comparing the results of r.sun with the ESRA database demonstrates that integration of the solar radiation model and the spatial interpolation tools in a GIS can be especially helpful for data at higher resolutions and in regions with a lack of ground measurements.

Regularized Spline with Tension (RST) is an accurate, flexible and efficient method for multivariate interpolation of scattered data. This study evaluates its capabilities to interpolate daily and annual mean precipitation in regions with complex terrain. Tension, smoothing and anisotropy parameters are optimized using the cross-validation technique. In addition, smoothing and rescaling of the third variable (elevation) is used to minimize the predictive error. The approach is applied to data sets from Switzerland and Slovakia and interpolation accuracy is compared to the results obtained by several other methods, expert-drawn maps and measured runoff. The results demonstrate that RST performs as well or better than the methods tested in the literature. The incorporation of terrain improves the spatial model of precipitation in terms of its predictive error, spatial pattern and water balance.

Modelling of erosion and deposition in complex terrain wilhin a geographical information system (GIs) requires a high resolution digital elevation model (DEM), reliable estimation of topographic parameters, and formulation of erosion models adequate for digital representation of spatially distributed parameters. Regularized spline with tension was integrated within a GIs for computation of DEMs and topographic parameters from digitized contours or other point elevation data. For construction of flow lines and computation of upslope contributing areas an algorithm based on vector-grid approach was developed. The spatial distribution of areas with topographic potential for erosion or deposition was then modelled using the approach based on the unit stream power and directional derivatives of surface representing the sediment transport capacity. The methods presented are illustrated on study areas in central Illinois and the Yakima Ridge, Washington.

Modelling of erosion and deposition in complex terrain wilhin a geographical information system (GIs) requires a high resolution digital elevation model (DEM), reliable estimation of topographic parameters, and formulation of erosion models adequate for digital representation of spatially distributed parameters. Regularized spline with tension was integrated within a GIs for computation of DEMs and topographic parameters from digitized contours or other point elevation data. For construction of flow lines and computation of upslope contributing areas an algorithm based on vector-grid approach was developed. The spatial distribution of areas with topographic potential for erosion or deposition was then modelled using the approach based on the unit stream power and directional derivatives of surface representing the sediment transport capacity. The methods presented are illustrated on study areas in central Illinois and the Yakima Ridge, Washington.

Soil erosion is a complex process determined by mutual interaction of numerous factors. The aim of erosion research at regional scales is a general evaluation of the landscape susceptibility to soil erosion by water, taking into account only main factors influencing this process. One of the main factors influencing the susceptibility of a region to soil erosion is land cover. This study describes the soil erosion assessment of Slovakia at a regional scale (1:500 000) using the USLE model and the CORINE land cover (CLC) database. The land cover/management factor (C factor) was derived from the CLC database by assigning the individual classes the appropriate value. In the second step, the C factor values for arable land (class 211) were refined using statistical data on the mean crop rotation and the acreage of particular agricultural crops in the districts of Slovakia.

This study presents a methodology for the assessment of photovoltaic potential in urban areas using open-source solar radiation tools and a 3-D city model implemented in a geographic information system (GIS). The solar radiation tools are represented by the r.sun solar radiation model and PVGIS estimation utility. The applicability of the methodology has been demonstrated on a selected urban area of a small city in eastern Slovakia. The relevant attributes of buildings have been mapped and implemented in a GIS database. The selected urban area consists of various urban zones characterized by different morphology and functionality. The photovoltaic potential of buildings has been assessed using the PVGIS estimation utility. The analysis has shown a high photovoltaic potential that could cover about 2/3 of current electricity consumption in the city. However, this potential exhibits large spatial and temporal variations caused by global and local factors. This study has also shown that national assessments of photovoltaic potential can be improved by extrapolation of local assessments using spatial databases of urban areas.