Rock-ring detection accuracy improvement in infrared satellite image with sub-pixel edge detection

The projection of space circle can be used for relative pose measurement of satellite targets. The accuracy of elliptical parameters plays an important role in the accuracy of pose recovery. However, the quality of space visible and infrared image is poor. The traditional ellipse detection method is mainly based on the edge of pixel-accuracy-wise and the ellipse accuracy is low, resulting in pose measurement errors. In this study, a sub-pixel-accuracy-wise edge-based ellipse fitting method is proposed to improve the ellipse accuracy. To realise this goal, we improved the arc-based ellipse detection method and designed sub-pixel-edge-based ellipse detection method. Experimental results show that the ellipse accuracy fitted by sub-pixel edge coordinates is at least 50% higher than that by pixel edge coordinates, especially when the ellipse is incomplete. The author's method is the first one to propose and verify the sub-pixel edge coordinate which contributes to enhancing ellipse accuracy.