Samira Karbasi; Hossein Malakooti; Mehdi Rahnama; Majid Azadi
Abstract
In this report, we compare data products from three different algorithms with the reference data obtained by ground-based high-resolution Fourier Transform Spectrometers (g-b FTSs) in the Total Carbon Column Observing Network (TCCON), with the 8 selected sites in five years(2011-2015). The algorithms ...
Read More
In this report, we compare data products from three different algorithms with the reference data obtained by ground-based high-resolution Fourier Transform Spectrometers (g-b FTSs) in the Total Carbon Column Observing Network (TCCON), with the 8 selected sites in five years(2011-2015). The algorithms evaluated are NIES, ACOS and SRFP algorithms. These algorithms are focused on retrieving the column abundance of the CO2 to take advantage of the molecular amounts of dry air carbon dioxide (XCO2). To evaluate the products of each algorithm with its equivalent ground observations, statistical indices such as Bias error, root mean square error (RMSE), absolute error (MAE), standard deviation (SD), and Pearson correlation coefficient (CR) were used. By examining the values presented by each algorithm and comparing it with the ground observation values, it can be concluded that the NIES, ACOS, and RemoTeC (SRFP) algorithms have the lowest RMSE, Bias and MAE error respectively. The best agreements with TCCON measurements in the most stations were detected for NIES 02.xx. The SRFP algorithm has a significant difference in estimating CO2 retrieving rates compared to the other two algorithms. So that the lowest correlation values belong to the SRFP algorithm and the highest correlation, values belong to the NIES algorithm.
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. ...
Read More
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.
