Block Adjustment without GCPs for Chinese Spaceborne SAR GF-3 Imagery.

Guo Zhang,Taoyang Wang,Mingjun Deng,Yu Zhu,Ruishan Zhao,Qingwei Wu,Xin Li,Fangting Li,Boyang Jiang,Huabin Wang

doi:10.3390/s18114023

Abstract

The Gaofen-3 (GF-3) satellite is the first C-band multi-polarization synthetic aperture radar (SAR) with the ability of high-accuracy mapping in China. However, the Ground Control Points (GCPs) are essential to ensure the accuracy of mapping for GF-3 SAR imagery at present. In this paper, we analyze the error sources that affect the geometric processing and propose a new block adjustment method without GCPs for GF-3 SAR imagery. Firstly, the geometric calibration of GF-3 image is carried out. Secondly, the rational polynomial coefficient (RPC) model is directly generated after the geometric calibration parameters compensation of each image. Finally, we solve the orientation parameters of the GF-3 images through DEM assisted planar block adjustment and conduct ortho-rectification. With two different imaging modes of GF-3 satellite, which include the QPSI and FS2, we carry out the block adjustment without GCPs. Experimental results of testing areas including Wuhan city and Hubei province in China show that the geometric mosaic accuracy and the absolute positioning accuracy of the orthophoto are better than one pixel, which has laid a good foundation for the application of GF-3 image in global high-accuracy mapping.

Highlights

Many spaceborne synthetic aperture radar (SAR) systems in the world already have the ability of high-accuracy geometric positioning and mapping
The results show that the satellite positioning accuracy improved by three m [10]
Geometric Calibration of Spaceborne SAR is to find out and calculate the main error sources leading to geometric positioning system errors

Summary

Introduction

Many spaceborne SAR systems in the world already have the ability of high-accuracy geometric positioning and mapping. The oldest SAR satellite is the European ERS satellite, and its plane positioning accuracy can reach 10 m [1]. The pixel location accuracy of the Sentinel-1A strip-map mode is at the sub-pixel level [2]. The COSMO-SkyMED satellite in Italy can achieve a geometric positioning accuracy of one m with the Spotlight-2 model [3]. For the TerraSAR-X satellite, the absolute positioning accuracy is 0.5 m in the azimuth direction and 0.3 m in the range direction [4]. The absolute location error (ALE) of Radarsat-2 is 17 m, which satisfies the system requirements of 40 m [5]

Methods

Results

Conclusion