František Zemek

Improved Temperature and Emissivity Separation Algorithm for Multispectral and Hyperspectral Sensors

The Temperature and Emissivity Separation (TES) algorithm was originally developed for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). This paper focuses on improving the TES algorithm. The main modification is the replacement of the normalized emissivity module with a new module, which is based on the smoothing of spectral radiance signatures. Smoothing is performed by estimating emissivity using an optimized approximation of the relationship between brightness temperature and emissivity. The improved TES algorithm, which is called Optimized Smoothing for Temperature Emissivity Separation (OSTES), was first tested on simulated data from three different sensors, namely, ASTER, Airborne Hyperspectral Scanner, and Thermal Airborne Spectrographic Imager. Processing simulated data with OSTES shows that it produces more accurate and precise temperature and emissivity retrievals than TES for samples with low spectral contrast. These results also show that the OSTES is less sensitive to variations in atmosphere and sample temperatures. The OSTES performance was secondly tested and compared with ASTER standard products. Testing showed that the OSTES temperature retrievals agree with AST_08 (kinetic temperature) but the emissivity retrievals differ substantially from AST_05 (surface emissivity). This implies that the ASTER standard products, AST_08 and AST_05, are not consistent with each other. Emissivities that are derived using temperatures from AST_08 and ASTER thermal surface radiances from AST_09T perform similar or worse when compared with OSTES emissivities. Emissivities delivered by AST_05 also exhibit step discontinuities, whereas the OSTES emissivitites are smoother over homogeneous surfaces. However, all emissivity spectra are affected by imperfect atmospheric corrections.

Relationships between the normalised difference vegetation index and temperature fluctuations in post-mining sites

Abstract The effects of age, vegetation density (normalised difference vegetation index [NDVI]) and vegetation type on temperature fluctuations were studied in post-coal-mining sites in the Czech Republic. NDVI and surface temperature were obtained from an airborne multispectral aerial photograph and FLIR infrared camera. The difference between morning and afternoon temperature was assumed as a measure of the temperature buffering ability of the ecosystem. Buffering increased with increasing NDVI but also depended on the type of vegetation, reclaimed sites have significantly higher buffering than unreclaimed sites. In contrary to grasslands, woody vegetation gradually increased temperature buffering capacity with plot age. Topsoil application substantially increased buffering capacity.

Analysing changes in land cover in relation to environmental factors in the districts of Znojmo and Třebíč (Czech Republic)

The aim of this study is to determine the influence of selected environmental factors on the dynamic changes in the landscape in the Czech Republic: 1) to detect land use changes between 1986–2013 along altitudinal gradients in two neighbouring Czech districts (Třebic and Znojmo), 2) to test if there is a relationship between the spatial distribution of the main changes and selected environmental factors, 3) to identify differences in the sizes of agricultural fields between 1953 and 2013, and whether they are associated with changes in agricultural land use. Satellite Landsat TM/ETM scenes for 1986, 1994, 2002 and 2013 were used to define land cover categories (arable land, grassland, coniferous forest, deciduous forest, mixed forest, urban areas and inland water). The association between the distribution of changes in land-cover with environmental factors such as gradient, aspect, altitude, topographic wetness index (TWI), less-favoured areas (LFA), main soil units and climate zones was determined. Only a limited proportion of landscape changes were dependent on environmental factors in the study area. Over the period 1994–2013 there was a decrease in arable land and increase in grassland, mainly in the LFA zone. Slope of the terrain was a dominating factor in landscape changes. The association with TWI values was most significant in permanent arable land and in grassland in transition to arable land. There was an increasing trend in the annual average temperature and sum of solar radiation in both the districts, Třebic and Znojmo. A change from small fields (1953) to large fields (2013) was recorded in the study area. Distribution of field sizes was different in LULC classes for different climatic zones and the main soil units.