中文摘要：

影像中圆形标志点的定位对于数字摄影测量具有重要作用。通过对圆形标志点边缘处的混合像素进行亚像素定位，提取出标志点的亚像素级边缘，再基于最小二乘原理进行椭圆拟合得到圆形标志的中心坐标。运用三种实验表明，与直接采用像素级边缘进行拟合定位相比，该方法的精度明显提高。

英文摘要：

The location of circle target in the image is very important to digital photogrammetry .Sub-pixel edge positions of the target are got by sub-pixel location in mixed pixels of the target edge .Then ,the center position of the circle target are calculated by the least squares elliptical fitting .Three experiments prove that the precision of this location method is higher than the precision of traditional method that elliptical fitting with pixel edge .