FATEMEH KAFI; Elham Yousefi; FATEMEH Jahanishakib
Abstract
The world is warming and the world's population is moving to cities. These two truths do not seem to be related; But a phenomenon called urban heat island connects the two. UHI is one of the most common urban climate phenomena in which some urban areas, especially urban centers, become several degrees ...
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The world is warming and the world's population is moving to cities. These two truths do not seem to be related; But a phenomenon called urban heat island connects the two. UHI is one of the most common urban climate phenomena in which some urban areas, especially urban centers, become several degrees warmer than the surrounding areas. Studying this phenomenon and examining its mechanism is very important for urban planning. In the present study, in order to estimate LST, four single-channel Landsat algorithms, single window, Planck equation and radiation transfer equation in QGIS software environment between 2000 and 2019 in summer and winter seasons in Birjand city have been used. The effect of land use change on the thermal island has also been investigated. In the present study, ground surface temperature in Birjand city was first extracted using Landsat 7 ETM + satellite imagery and Landsat 8 TIRS / OLI sensors in 2000 and 2019 by four methods. In order to investigate the general ability of algorithms to calculate the surface temperature, the statistical indices of mean square error, Nash-Sutcliffe coefficient, mean absolute error and coefficient of determination were used. The results showed that the Landsat single-channel algorithm for calculating the surface temperature in Birjand is more accurate than other algorithms.
Sara Attarchi; Mehdi Rahnama
Abstract
Full polarimetric SAR sensors can capture full polarimetric characteristics of targets. Therefore, in comparison with single and dual polarimetric sensors they offer more capabilities in target detection. However, operation in full polarimetric mode increases complexity, data volume and need more power. ...
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Full polarimetric SAR sensors can capture full polarimetric characteristics of targets. Therefore, in comparison with single and dual polarimetric sensors they offer more capabilities in target detection. However, operation in full polarimetric mode increases complexity, data volume and need more power. Full polarimetric sensors acquire images with less swath compared to dual mode. As a result, most of SAR sensors operate in dual mode and provide dual polarimetric images. Due to high availability, dual polarimetric images are increasingly being used in many researches. In this research, the efficiency of dual polarimetric images is compared with full polarimetric mode. The main goal is to find the best combination of two polarimetric bands which has the nearest results to full polarimetric mode.One Advanced Land Observing Satellite / Phased Array L-band Synthetic Aperture Radar scene had been processed. The scene was multi-looked and converted to the backscattering coefficient (sigma nought, dB). The image was decomposed by cluode-pottier method into alpha and entropy components. Three different combination of two polarimetric bands were considered; HH-HV; HH-VV and HV-VV. Alpha and entropy of each dual polarimetric mode were also computed. Then alpha and entropy driven from full-polarimetric mode were separately compared with alpha and entropy of each dual mode. Since different land cover types (i.e. built-up, cropland, bare land and water) exist in the scene, the computations were done separately for each land cover type. The comparison among alpha values from full polarimetric mode and dual polarimetric mode reveals that HH-HV combination shows the best conformity with full polarimetric mode. HH-VV dual mode has the poorest results. Entropy values of HH-HV mode had the least difference with full polarimetric mode. Entropy values of HH-VV shows the weakest similarity. The MAE values of HH-HV, HH-VV and HV-VV were 0.06, 0.22 and 0.17, respectively. The findings of this research shows that polarimetric features driven from HH-HV combination are more compatible with full-polarimetric mode. In case, no full polarimetric image is available, this dual combination can be substituted. Based on quantitative results, HH-HV combination is recommended to be used in case no full polarimetric image is availableOne Advanced Land Observing Satellite / Phased Array L-band Synthetic Aperture Radar scene had been processed. The scene was multi-looked and converted to the backscattering coefficient (sigma nought, dB). The image was decomposed by cluode-pottier method into alpha and entropy components. Three different combination of two polarimetric bands were considered; HH-HV; HH-VV and HV-VV. Alpha and entropy of each dual polarimetric mode were also computed. Then alpha and entropy driven from full-polarimetric mode were separately compared with alpha and entropy of each dual mode. Since different land cover types (i.e. built-up, cropland, bare land and water) exist in the scene, the computations were done separately for each land cover type. The comparison among alpha values from full polarimetric mode and dual polarimetric mode reveals that HH-HV combination shows the best conformity with full polarimetric mode. HH-VV dual mode has the poorest results. Entropy values of HH-HV mode had the least difference with full polarimetric mode. Entropy values of HH-VV shows the weakest similarity. The MAE values of HH-HV, HH-VV and HV-VV were 0.06, 0.22 and 0.17, respectively. The findings of this research shows that polarimetric features driven from HH-HV combination are more compatible with full-polarimetric mode. In case, no full polarimetric image is available, this dual combination can be substituted. Based on quantitative results, HH-HV combination is recommended to be used in case no full polarimetric image is available.
