Because of difference on the gray - level and resolution - level between multi - source images, it is very difficult to register two images.

不同源图像间由于灰度和分辨率水平上的显著差异，使得两图像间的配准问题十分困难。

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This paper mainly studies the extraction of high-altitude targets, particularly for airspace object because of the gray level difference of target and background.

本文主要研究对空域目标的提取，针对空域目标和背景特殊的灰度差异性对目标进行分离。

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