基于SNR的GPS-IR技术机理分析
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摘要
鉴于现有研究对GPS-IR技术的反射波接收、低高度角信噪比观测值的使用、信噪比残差的形态等机理还未阐释清楚,且几乎是通过实验进行解释,因此,从理论和实验2个方面对GPS-IR技术机理进行分析。理论和实验证明:GPS卫星发射的右旋圆极化波经一次反射后部分转换为左旋圆极化波,转换比例随着高度角和介电常数增大而变大,当右旋圆极化波垂直入射到理想导体表面时,经一次反射才能全部转换为左旋圆极化波;同时在测量型GPS接收机安装有抑径板的情况下,因衍射现象的存在,测量型GPS接收机天线仍能接收反射波中的右旋圆极化波。当高度角越小或介电常数越大时,GPS入射波中的垂直极化波和平行极化波的能量透射到反射物中就越少,其反射波的强度就越大,信噪比受反射波影响就越严重,且能够接收的右旋圆极化波较多,因此GPS-IR使用的是低高度角(如30°以下)的信噪比观测值。当高度角变化范围较小时,信噪比残差序列呈近似"余弦曲线"形态,从而建立了基于信噪比残差的反演模型。
The available research on technology mechanism of reflected wave reception,the use of the SNR observations of low elevating angle and the form of SNR residuals for GPS-IR is not clear enough,and they are almost interpreted by experiments. This paper analyzed the GPS-IR technology mechanism from the aspects of theories and experiments. The right hand circular polarized wave transmitted by GPS satellite is partly converted into left hand circular polarized wave after one reflection,and the conversion ratio increases with the increase of satellite elevating angle and dielectric constant. When the right hand circular polarized wave is perpendicular to the surface of the perfect conductor,it can be all converted into left hand circular polarized wave after a reflection;At the same time,in the case of the measuring GPS receiver equipped with the baffle plate,because of the diffraction phenomenon,the antenna of the measuring GPS receiver can still receive the right hand circular polarized wave in the reflected signal. When the elevating angle is smaller or the dielectric constant of the reflector is larger,the less GPS incident wave energy of vertically polarized wave and parallel polarized wave is transmitted to the reflector. The more intense the reflected wave is,the worse the SNR is affected by the reflected wave,and there are more right hand circular polarized waves that can be received. Therefore,the GPS-IR uses the SNR observations of low elevating angle(such as under 30°). When the elevating angle changes and the range is smaller,the SNR residuals sequence is approximately "cosine curve",and thus,an inversion model based on SNR residuals is established.
The available research on technology mechanism of reflected wave reception,the use of the SNR observations of low elevating angle and the form of SNR residuals for GPS-IR is not clear enough,and they are almost interpreted by experiments. This paper analyzed the GPS-IR technology mechanism from the aspects of theories and experiments. The right hand circular polarized wave transmitted by GPS satellite is partly converted into left hand circular polarized wave after one reflection,and the conversion ratio increases with the increase of satellite elevating angle and dielectric constant. When the right hand circular polarized wave is perpendicular to the surface of the perfect conductor,it can be all converted into left hand circular polarized wave after a reflection;At the same time,in the case of the measuring GPS receiver equipped with the baffle plate,because of the diffraction phenomenon,the antenna of the measuring GPS receiver can still receive the right hand circular polarized wave in the reflected signal. When the elevating angle is smaller or the dielectric constant of the reflector is larger,the less GPS incident wave energy of vertically polarized wave and parallel polarized wave is transmitted to the reflector. The more intense the reflected wave is,the worse the SNR is affected by the reflected wave,and there are more right hand circular polarized waves that can be received. Therefore,the GPS-IR uses the SNR observations of low elevating angle(such as under 30°). When the elevating angle changes and the range is smaller,the SNR residuals sequence is approximately "cosine curve",and thus,an inversion model based on SNR residuals is established.
引文
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[15] Wu Jizhong,Yang Ronghua. Measuring water surface height by using reflected signal of geodetic-quality GPS receiver[J].Journal of Geodesy and Geodynamics,2012,32(6):135-138.[吴继忠,杨荣华.利用GPS接收机反射信号测量水面高度[J].大地测量与地球动力学,2012,32(6):135-138.]
[16] Zhang Shuangcheng,Nan Yang,Li Zhenyu,et al. Analysis of tide variation monitored by GNSS-MR[J]. Acta Geodaetica et Cartographica Sinica,2016,45(9):1 042-1 049.[张双成,南阳,李振宇,等.GNSS-MR技术用于潮位变化监测分析[J].测绘学报,2016,45(9):1 042-1 049.]
[17] Larson K M,Braun J J,Small E E,et al. GPS multipath and its relation to near-surface soil moisture content[J]. IEEE Journal of Selected Topics in Applied Earth Observations&Remote Sensing,2010,3(1):91-99.
[18] Zavorotny V U,Larson K M,Braun J J,et al. A physical model for GPS multipath caused by land reflections:Toward bare soil moisture retrievals[J]. IEEE Journal of Selected Topics in Applied Earth Observations&Remote Sensing,2010,3(1):100-110.
[19] Xiao Xiongxin,Zhang Tingjun. Passive microwave remote sensing of snow depth and snow water equivalent:Overview[J]. Advances in Earth Science,2018,33(6):590-605.[肖雄新,张廷军.基于被动微波遥感的积雪深度和雪水当量反演研究进展[J].地球科学进展,2018,33(6):590-605.]
[20] Xie Chufang,Rao Kejin. Electromagnetic Field and Electromagnetic Wave[M]. Beijing:Higher Education Press,2006.[谢处方,饶克谨.电磁场与电磁波[M].北京:高等教育出版社,2006.]
[21] Zhang Zhenglu,Si Shaoxian. Li Xuejun,et al. Detecting and Surveying of Underground Pipelines and Pipeline Information System[M]. Beijing:Surveying and Mapping Press,2007.[张正禄,司少先,李学军,等.地下管线探测和管网信息系统[M].北京:测绘出版社,2007.]
[22] Zavorotny V U,Voronovich A G. Scattering of GPS signals from the ocean with wind remote sensing application[J]. IEEE Transactions on Geoscience&Remote Sensing,2000,38(2):951-964.
[23] Wu Shiqi,Zhu Lidong. Introduction of Telecommunication System[M]. Beijing:Tsinghua University Press,2005.[吴诗其,朱立东.通信系统概论[M].北京:清华大学出版社,2005.]
[24] Yu K,Ban W,Zhang X,et al. Snow depth estimation using GPS triple-frequency carrier phase combination[J]. IEEE Transactions on Geoscience&Remote Sensing,2015,53(9):5 100-5 109.
[25] Wu Yuhang,Chen Xiuwan,Wu Caicong. Mitigation of multipath effect using SNR values[J]. Geomatics and Information Science of Wuhan University,2008,33(8):842-845.[吴雨航,陈秀万,吴才聪.利用信噪比削弱多路径误差的方法研究[J].武汉大学学报:信息科学版,2008,33(8):842-845.]
[2] Li Huang,Xia Qing,Yin Cong,et al. The current status of research on GNSS-R remote sensing technology in China and future development[J]. Journal of Radars,2013,2(4):389-399.[李黄,夏青,尹聪,等.我国GNSS-R遥感技术的研究现状与未来发展趋势[J].雷达学报,2013,2(4):389-399.]
[3] Yan Songhua,Gong Jianya,Zhang Xunxie,et al. Ground based GNSS-R observations for soil moisture[J]. Chinese Journal of Geophysics,2011,54(11):2 735-2 744.[严颂华,龚健雅,张训械,等.GNSS-R测量地表土壤湿度的地基实验[J].地球物理学报,2011,54(11):2 735-2 744.]
[4] Liu Jingnan,Shao Lianjun,Zhang Xunxie. Advances in GNSSR studies and key technologies[J]. Geomatics and Information Science of Wuhan University,2007,32(11):955-960.[刘经南,邵连军,张训械.GNSS-R研究进展及其关键技术[J].武汉大学学报:信息科学版,2007,32(11):955-960.]
[5] Sun Xiaorong,Liu Zhiliang,Zheng Nanshan,et al. Two new algorithms for position estimation of GNSS-R specular reflection point[J]. Journal of China University of Mining&Technology,2017,46(4):917-923.[孙小荣,刘支亮,郑南山,等.两种新的GNSS-R镜面反射点位置估计算法[J].中国矿业大学学报,2017,46(4):917-923.]
[6] Li Zhenghang,Huang Jinsong. GPS Surveying and Data Processing[M]. Wuhan:Wuhan University Press,2010.[李征航,黄劲松.GPS测量与数据处理[M].武汉:武汉大学出版社,2010.]
[7] Bilich A,Axelrad P,Larson K M. Scientific utility of the Signal-to-Noise Ratio(SNR)reported by geodetic GPS receivers[J]. Proceedings of International Technical Meeting of the Satellite Division of the Institute of Navigation,2007,2:1 999-2 010.
[8] Larson K M,Small E E,Gutmann E,et al. Using GPS multipath to measure soil moisture fluctuations:Initial results[J].GPS Solutions,2008,12(3):173-177.
[9] Larson K M,Gutmann E D,Zavorotny V U,et al. Can we measure snow depth with GPS receivers?[J]. Geophysical Research Letters,2009,36(17):153-159.
[10] Jacobson M D. Inferring snow water equivalent for a snow-covered ground reflector using GPS multipath signals[J]. Remote Sensing,2010,2(10):2 426-2 441.
[11] Nievinski F G,Larson K M. Forward modeling of GPS multipath for near-surface reflectometry and positioning applications[J]. GPS Solutions,2014,18(2):309-322.
[12] Nievinski F G,Larson K M. Inverse modeling of GPS multipath for snow depth estimation—Part I:Formulation and simulations[J]. IEEE Transactions on Geoscience&Remote Sensing,2014,52(10):6 555-6 563.
[13] Nievinski F G,Larson K M. Inverse modeling of GPS multipath for snow depth estimation—Part II:Application and validation[J]. IEEE Transactions on Geoscience&Remote Sensing,2014,52(10):6 564-6 573.
[14] Ao Minsi,Zhu Jianjun,Hu Youjian,et al. Comparative experiments on soil moisture monitoring with GPS SNR observations[J]. Geomatics and Information Science of Wuhan University,2015,40(1):117-120,127.[敖敏思,朱建军,胡友健,等.利用SNR观测值进行GPS土壤湿度监测[J].武汉大学学报:信息科学版,2015,40(1):117-120,127.]
[15] Wu Jizhong,Yang Ronghua. Measuring water surface height by using reflected signal of geodetic-quality GPS receiver[J].Journal of Geodesy and Geodynamics,2012,32(6):135-138.[吴继忠,杨荣华.利用GPS接收机反射信号测量水面高度[J].大地测量与地球动力学,2012,32(6):135-138.]
[16] Zhang Shuangcheng,Nan Yang,Li Zhenyu,et al. Analysis of tide variation monitored by GNSS-MR[J]. Acta Geodaetica et Cartographica Sinica,2016,45(9):1 042-1 049.[张双成,南阳,李振宇,等.GNSS-MR技术用于潮位变化监测分析[J].测绘学报,2016,45(9):1 042-1 049.]
[17] Larson K M,Braun J J,Small E E,et al. GPS multipath and its relation to near-surface soil moisture content[J]. IEEE Journal of Selected Topics in Applied Earth Observations&Remote Sensing,2010,3(1):91-99.
[18] Zavorotny V U,Larson K M,Braun J J,et al. A physical model for GPS multipath caused by land reflections:Toward bare soil moisture retrievals[J]. IEEE Journal of Selected Topics in Applied Earth Observations&Remote Sensing,2010,3(1):100-110.
[19] Xiao Xiongxin,Zhang Tingjun. Passive microwave remote sensing of snow depth and snow water equivalent:Overview[J]. Advances in Earth Science,2018,33(6):590-605.[肖雄新,张廷军.基于被动微波遥感的积雪深度和雪水当量反演研究进展[J].地球科学进展,2018,33(6):590-605.]
[20] Xie Chufang,Rao Kejin. Electromagnetic Field and Electromagnetic Wave[M]. Beijing:Higher Education Press,2006.[谢处方,饶克谨.电磁场与电磁波[M].北京:高等教育出版社,2006.]
[21] Zhang Zhenglu,Si Shaoxian. Li Xuejun,et al. Detecting and Surveying of Underground Pipelines and Pipeline Information System[M]. Beijing:Surveying and Mapping Press,2007.[张正禄,司少先,李学军,等.地下管线探测和管网信息系统[M].北京:测绘出版社,2007.]
[22] Zavorotny V U,Voronovich A G. Scattering of GPS signals from the ocean with wind remote sensing application[J]. IEEE Transactions on Geoscience&Remote Sensing,2000,38(2):951-964.
[23] Wu Shiqi,Zhu Lidong. Introduction of Telecommunication System[M]. Beijing:Tsinghua University Press,2005.[吴诗其,朱立东.通信系统概论[M].北京:清华大学出版社,2005.]
[24] Yu K,Ban W,Zhang X,et al. Snow depth estimation using GPS triple-frequency carrier phase combination[J]. IEEE Transactions on Geoscience&Remote Sensing,2015,53(9):5 100-5 109.
[25] Wu Yuhang,Chen Xiuwan,Wu Caicong. Mitigation of multipath effect using SNR values[J]. Geomatics and Information Science of Wuhan University,2008,33(8):842-845.[吴雨航,陈秀万,吴才聪.利用信噪比削弱多路径误差的方法研究[J].武汉大学学报:信息科学版,2008,33(8):842-845.]
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