Liu Lirong, Xie Junfeng, Tang Xinming, Ren Chaofeng, Chen Jiyi, Liu Ren
Land Satellite Remote Sensing Application Center, MNR, Beijing 100048, China.
College of Geological Engineering and Geomatics, Chang'an University, Xi'an 710054, China.
Sensors (Basel). 2021 Mar 25;21(7):2297. doi: 10.3390/s21072297.
The GF-7 satellite is China's first high-resolution stereo mapping satellite that reaches sub-meter resolution, equipped with new-type payloads, such as an area array footprint camera that can achieve synchronization acquisition of laser spots. When the satellite is in space, the variation of camera parameters may occur due to launch vibration and environmental changes, and on-orbit geometric calibration thereby must be made. Coupled with the data from the GF-7 satellite, this paper constructs a geometric imaging model of the area array footprint camera based on the two-dimensional direction angle, and proposes a coarse-to-fine "LPM-SIFT + Phase correlation" matching strategy for the automatic extraction of calibration control points. The single-image calibration experiment shows that the on-orbit geometric calibration model of the footprint camera constructed in this paper is correct and effective. The matching method proposed is used to register the footprint images with the DOM (Digital Orthophoto Map) reference data to obtain dense control points. Compared with the calibration result using a small number of manually collected control points, the root mean square error (RMSE) of the residual of the control points is improved from half a pixel to 1/3, and the RMSE of the same orbit checkpoints in the image space is improved from 1 pixel to 0.7. It can be concluded that using the coarse-to-fine image matching method proposed in this paper to extract control points can significantly improve the on-orbit calibration accuracy of the footprint camera on the GF-7 satellite.
高分七号卫星是中国首颗达到亚米级分辨率的高分辨率立体测绘卫星，搭载了新型载荷，如能实现激光点同步采集的面阵推扫式相机。卫星在太空运行时，由于发射振动和环境变化，相机参数可能会发生变化，因此必须进行在轨几何校准。结合高分七号卫星数据，本文基于二维方向角构建了面阵推扫式相机的几何成像模型，并提出了一种由粗到精的“LPM - SIFT + 相位相关”匹配策略用于自动提取校准控制点。单幅图像校准实验表明，本文构建的推扫式相机在轨几何校准模型正确有效。所提出的匹配方法用于将推扫图像与DOM（数字正射影像图）参考数据配准以获取密集控制点。与使用少量人工采集控制点的校准结果相比，控制点残差的均方根误差（RMSE）从半个像素提高到了1/3像素，图像空间中同一轨道检查点的RMSE从1像素提高到了0.7像素。可以得出结论，利用本文提出的由粗到精的图像匹配方法提取控制点，可显著提高高分七号卫星上推扫式相机的在轨校准精度。
