This paper introduces three methods of eliminating shadow on airborne SAR images, which are increasing overlap ratio,
imaging on both sides and imaging on across orientation. Reason and factors of causing shadow is analyzed in this paper.
The effect of eliminating shadow using the three methods mentioned is analyzed quantitatively. Given the side-looking
angle is from 20 degree to 70 degree. When the slope of reversing side-looking orientation is smaller than 70 degree, if
SAR images' overlap ratio is 75%, shadow incidence can be reduced to the slope from 57.5 degree to 70 degree. At the
same time, if imaging on both sides is used, shadow can be eliminated absolutely when the slope of one side is between
57.5 degree to 70 degree, and shadow can be eliminated in the condition of vale bottom's width is more than the
threshold value mentioned in this paper when the slopes of both sides are between 57.5 degree to 70 degree. When the
slope of reversing side-looking orientation is bigger than 70 degree and vale bottom's width is less than the threshold
value mentioned in this paper, air line which flight track is across vale can be adopted in order to avoiding shadow effect.
The reasons caused shadow by terrain and eliminating methods used are analyzed in Hengduan Mountain area, air lines
are designed in this area for obtaining airborne SAR images based on above.