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The effects of orbit type on synthetic aperture RADAR (SAR) backscatter

Mahdavi, Sahel, Amani, Meisam, Maghsoudi, Yasser
Remote sensing letters 2019 v.10 no.2 pp. 120-128
evapotranspiration, ground vegetation, remote sensing, roughness, spring, synthetic aperture radar, tree classes, trees, water content, wind speed, winter
The difference between an image pair acquired in crossing orbits of Synthetic Aperture Radar (SAR) sensors is of great importance. In this study, this difference was investigated in terms of backscatter and scattering mechanisms for several classes, including the Ground Vegetation (Gv), Water (Wtr), and Trees. Two RADARSAT-2 image pairs were used, one in spring and the other in winter. Almost all conditions were similar for each image pair except for the type of orbit. In the spring image pair, the backscatter for almost all classes from the image in the ascending orbit was more than that from the image captured in the descending mode. This was attributed to the change in the amount of evapotranspiration and the water content for the Gv and Tree classes, and was the result of wind speed variation for the Wtr class. For the winter image pair however, no significant difference was observed between the images acquired in the crossing orbits. The reason was that all the classes were frozen and, therefore, no evapotranspiration and roughness change occurred in that time. The results of this study proved that the difference between the images captured from crossing SAR orbits should be taken into account.