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Remote sensing techniques are powerful tools for the validation and data assimilation of GIS-based calculations of physical and distributed hydrological models. The high spatial resolution of Landsat TM, ETM+ and OLI, make this the most adequate satellite images for the study of hydrological processes in Mediterranean regions. Several levels of preprocessing are required to obtain validated reflectance values from these images. Generally, these steps include radiometric calibrations and an atmospheric correction. However, over complex terrain and for specific land covers such as snow, certain problems related to radiometric saturation and shadow effects must also be taken into account. This work presents a graphic user interface (GUI), developed in MATLAB, which comprises all this preprocess. The only inputs required by the GUI are the metadata file of each Landsat images together with the digital elevation model (DEM) of the study area. The users can select among different preprocessing steps depending on their needs. Four processes have been implemented: (1) Radiometric calibration, through the use of calibration coefficients described in metadata files; (2) atmospheric correction, by using dark object subtraction (DOS); (3) saturation problem, by means of a multivariable correlation analysis between saturated and non-saturated bands; and (4) topographic correction, which is implemented thanks to C-Correction algorithm. The users can also choose the format of the output images (ascii ArcGIS, ascii ENVI and GEOTIFF) based on their final applications. This GUI allows faster results than other Landsat images preprocessing applications, due to the analysis of particular selected areas and the inclusion of a simple but accurate atmospheric correction, when the atmospheric properties that are needed on more complex models are not available at the study site.


Session R76, Use of Remote Sensing Techniques



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