稀少控制的多平台星载SAR联合几何定标方法

几何定标采用地面控制点获取距离-多普勒模型中的精确几何参数，用于完成星载SAR影像高精度几何定位。但在广域范围内，特别是高山地区域，控制点极难获取。此外，传统定标方法仅面向单一平台SAR影像，尚不能实现多平台影像的联合几何定标。针对上述问题，本文提出一种基于稀少控制的多平台星载SAR联合几何定标方法。该方法从包含实测控制点的主影像出发，使用点位追踪算法获取主影像与从影像之间的连接点，并以连接点为桥梁逐级完成从影像的几何定标。本文采用京津冀地区南北向分布共计235 km的3景TerraSAR-X、3景TanDEM-X、5景高分三号影像进行联合几何定标试验，仅使用5个控制点即完成了所有影像的几何定标，并利用SF-3050星站差分GNSS接收机采集实测GPS点进行精度评价。结果表明使用稀少控制点定标后的TSX/TDX影像的几何定位精度优于3 m，GF-3影像的几何定位精度优于7.5 m，验证了该方法的有效性和正确性。

Hybrid Geometric Calibration Method for Multi-platform Spaceborne SAR Image with Sparse GCPs

Geometric calibration is able to provide high-accuracy geometric coordinates of spaceborne SAR image through accurate geometric parameters in the Range-Doppler model by ground control points (GCPs).However, it is very difficult to obtain GCPs that covering large-scale areas, especially in the mountainous regions.In addition, the traditional calibration method is only used for single platform SAR images and can't support the hybrid geometric calibration for multi-platform images.To solve the above problems, a hybrid geometric calibration method for multi-platform spaceborne SAR images with sparse GCPs is proposed in this paper.First, we calibrate the master image that contains GCPs.Secondly, the point tracking algorithm is used to obtain the tie points (TPs) between the master and slave images.Finally, we calibrate the slave images using TPs as the control points.We take the Beijing-Tianjin-Hebei region as an example to study SAR image hybrid geometric calibration method using 3 TerraSAR-X images, 3 TanDEM-X images and 5 GF-3 images covering more than 235 kilometers in the north-south direction.Geometric calibration of all images is completed using only 5 GCPs.The GPS data extracted from GNSS receiver are used to assess the plane accuracy after calibration.The results after geometric calibration with sparse GCPs show that the geometric positioning accuracy is 3 m for TSX/TDX images and 7.5 m for GF-3 images.