利用星下点干涉相位法提高三维成像高度计测高精度
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摘要
基线倾角是三维成像高度计获取海表面高度的一个重要参数。基线倾角误差造成的高程误差随着交轨距离增加而增大。微小的基线倾角误差在整个观测刈幅内会引起大幅度的高程测量误差,因此精确获得基线倾角值是十分必要的。星下点干涉相位与基线倾角具有较强的相关性,利用二者之间的关系进行基线倾角的计算可以获得比一般硬件测量更高的基线倾角测量精度,进而对基线倾角误差进行校正,以满足厘米级测高精度的需求。通过在仿真海面上进行基于几何关系模拟测量与高程重建,可以进行利用星下点干涉相位法校正基线倾角误差的研究。对已设定三维成像高度计的系统参数进行数值模拟,结果表明:在10-3 rad的干涉相位测量精度条件下,基线倾角精度可以达到0.03角秒,在10～60km刈幅范围内,对高程平均测量精度的影响由模拟硬件测量得到的0.36角秒对应的6.02cm降低至0.48cm,与理论计算结果一致,说明星下点干涉相位法能够有效地对基线倾角误差进行校正。
Roll angle is an important parameter for three-dimensional imaging altimeter to measure Sea Surface Height.The height error due to the roll angle error grows linearly across the swath and a slight error of roll angle will results in a large height error within observation range.So a very accurate knowledge of the roll angle error is required.Nadir interferometric phase has a strong correlation with the roll angle,so using the nadir interferometric phase from the interference image can get roll angle more accurately than instrument measurements.It's possible to meet the centimeter-level accuracy after correcting the roll angle error.Simulation measurement and elevation reconstruction based on the geometric relationship were performed,and the research of correction the roll angle error by nadir interferometric phase was carried out.Both theoretical calculation and numerical simulation show that the measurement accuracy of roll angle can be as high as 0.03 arcsecond when the accuracy of nadir interferometric phase is 10-3 rad.In this case,the height measurement accuracy have been averaged across a swath between 10 and 60 km of nadir will decrease to 0.48 cm which is 6.02 cm when the roll accuracy is 0.36 arcsecond.It means that the nadir interferometric phase method can effectively correct the roll error of three-dimensional imaging altimeter.
Roll angle is an important parameter for three-dimensional imaging altimeter to measure Sea Surface Height.The height error due to the roll angle error grows linearly across the swath and a slight error of roll angle will results in a large height error within observation range.So a very accurate knowledge of the roll angle error is required.Nadir interferometric phase has a strong correlation with the roll angle,so using the nadir interferometric phase from the interference image can get roll angle more accurately than instrument measurements.It's possible to meet the centimeter-level accuracy after correcting the roll angle error.Simulation measurement and elevation reconstruction based on the geometric relationship were performed,and the research of correction the roll angle error by nadir interferometric phase was carried out.Both theoretical calculation and numerical simulation show that the measurement accuracy of roll angle can be as high as 0.03 arcsecond when the accuracy of nadir interferometric phase is 10-3 rad.In this case,the height measurement accuracy have been averaged across a swath between 10 and 60 km of nadir will decrease to 0.48 cm which is 6.02 cm when the roll accuracy is 0.36 arcsecond.It means that the nadir interferometric phase method can effectively correct the roll error of three-dimensional imaging altimeter.
引文
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[3] Xu Xiyu.Study on Spaceborne Radar Altimeter Error Analysis and Calibration Technology[D].Beijing:Chinese Academy of Sciences and Graduate University:Center for Space Science and Applied Research,2008.[徐曦煜.星载雷达高度计误差分析和定标技术研究[D].北京:中国科学院研究生院:空间科学与应用研究中心,2008.]
[4] Xu Ke,Dong Xiaolong,Zhang Dehai,et al.HY-2Radar Altimeter and Microwave Scatterometer[J].Remote Sensing Technology and Application,2005,20(1):89-93[许可,董晓龙,张德海,等.HY-2雷达高度计和微波散射计[J].遥感技术与应用,2005,20(1):89-93.]
[5] Cai Yulin,Cheng Xiao,Sun Guoqing.A Review of Development of Radar Altimeter and Its Applications[J].Remote Sensing Information,2006,(4):74-78,87.[蔡玉林,程晓,孙国清.星载雷达高度计的发展及应用现状[J].遥感信息,2006,(4):74-78,87.]
[6] Xu Yongsheng,Gao Le,Zhang Yunhua.New Generation Altimetry Satellite SWOT and Its Reference to China’s Swath Altimetry satellite[J].Remote Sensing Technology and Application,2017,32(1):84-94.[徐永生,高乐,张云华.美国新一代测高卫星SWOT——评述我国宽刈幅干涉卫星的发展借鉴[J].遥感技术与应用,2017,32(1):84-94.]
[7] Ducet N,Traon P Y L,Reverdin G.Global High-resolution Mapping of Ocean Circulation from TOPEX/Poseidon and ERS-1and-2[J].Journal of Geophysical Research Oceans,2000,105(C8):19477-19498.
[8]Yang Shuangbao,Zhai Zhenhe,Xu Ke,et al.The Ground Process Segment of SAR Altimeter[J].Remote Sensing Technology and Application,2017,32(6):1083-1092.[杨双宝,翟振和,许可,等.合成孔径雷达高度计数据处理方法[J].遥感技术与应用,2017,32(6):1083-1092.]
[9] Rosen P A,Hensley S,Joughin I R,et al.Synthetic Aperture Radar Interferometry[J].Proceedings of the IEEE,2002,88(3):333-382.
[10] Fu L L,Rodriguez R.State of the Planet:Frontiers and Challenges in Geophysics[M].Chapter:High-resolution Measurement of Ocean Surface Topography by Radar Interferometry for Oceanographic and Geophysical Applications.Washingto,D.C.:Geophysical Monograph,American Geophysical Union,2004,150:209-224.
[11] Cao Xiaochen,You Hongjian,Liu Jiayin,et al.Research on Accuracy Enhancement Method of SRTM based on Error Model[J].Remote Sensing Technology and Application,2017,32(5):801-805.[曹晓晨,尤红建,刘佳音,等.基于误差建模的SRTM高程精度提升方法研究[J].遥感技术与应用,2017,32(5):801-805.]
[12] Fu L L,Vaze P.The Surface Water and Ocean Topography Mission:Centimetric Spaceborne Radar Interferometry[J].Proceedings of SPIE,2010,7826:455-461.
[13] Gaultier L,Ubelmann C,Fu L L.The Challenge of Using Future SWOT Data for Oceanic Field Reconstruction[J].Journal of Atmospheric&Oceanic Technology,2015,33(1):119-126.
[14] Zheng Fang,Ma Debao,Pei Huaining.Discussion about Requirement of Base Line Precision in InSAR[J].Modem Radar2005.(9):18-21.[郑芳,马德宝,裴怀宁.InSAR中基线精度要求的探讨[J].现代雷达,2005,(9):18-21.]
[15] Geng Hui,Xie Yanan,Wang bo,et al.Elevation Measurement of InSAR and Accuracy Analysis[J].Electronic Measurement Technology,2011,34(2):39-41,65.[耿辉,谢亚楠,王波,等.InSAR测高原理及精度分析[J].电子测量技术,2011,34(2):39-41,65.]
[16] Zhang Y,Zhai W,Gu X,et al.Experimental Demonstration for the Attitude Measurement Capability of Interferometric Radar Altimeter[C]∥15th International Radar Symposium Proceedings,2014.
[17] Jin Guowang,Xu qing,Zhang Hongmin.Synthetic Aperture Radar Interferometry[M].Beijing:National Defend Industry Press,2014.[靳国旺,徐青,张红敏.合成孔径雷达干涉测量[M].北京:国防工业出版社,2014.]
[18] Daniel E F,Fu L L,Brian P,et al.SWOT Project Mission Performance and Error Budget Document[DB/OL].https:∥swot.jpl.nasa.gov/docs/SWOT_D-79084_v10Y_FINAL_REVA__06082017.pdf.