14 March 2003 Simultaneous correction of bidirectional effects in line scanner images of rural areas
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The most prominent artifact in line scanner images is a cross track brightness gradient, which is due to sensor optics, atmospheric and surface bidirectional effects. Those effects prevent a precise intra- and intercomparison of image scenes and affect spectral ratios. A method to improve the intra- and intercomparison of a set of images of the same surface type but from different times of the day by using a simultaneous correction of bidirectional effects is presented. It should be applied after sensor, atmospheric, and geometric correction, although all four effects interact with each other. But since the method is semi-empirical in nature it will also correct partly gradients from the other effects when applied solely. The method bases on the linear semi-empirical Ambrals model (Algorithm for MODIS Bidirectional Reflectance Anisotropy of the Land Surface, Lucht 2000). A ready-to-use software in IDL has been developed for line scanner images and is made available to the public for test. The adaptation to different sensor types is straightforward. As an example, images from the DAISEX'99 campaign in Barrax, taken with the wide FOV hyperspectral sensor HyMap from different flight directions and times of the day, are modeled and corrected. An intercomparison of the images and a validation is made.
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Ulrich Beisl "Simultaneous correction of bidirectional effects in line scanner images of rural areas", Proc. SPIE 4886, Remote Sensing for Environmental Monitoring, GIS Applications, and Geology II, (14 March 2003); doi: 10.1117/12.463284; https://doi.org/10.1117/12.463284

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