地基差分干涉雷达发展现状及应用实例

曾涛; 邓云开; 胡程; 田卫明

doi:10.12000/JR18115

地基差分干涉雷达发展现状及应用实例

DOI: 10.12000/JR18115

曾涛¹,
邓云开^1, ,,
胡程²,
田卫明²

①.
北京理工大学信息与电子学院雷达技术研究所北京 100081
②.
北京理工大学卫星导航电子信息技术教育部重点实验室北京 100081

基金项目: 国家自然科学基金(61427802, 61601031)，国家杰出青年科学基金(61625103)，长江学者奖励计划(T2012122)

详细信息

作者简介:
邓云开(1992–)，男，河南人，北京理工大学博士研究生，主要研究方向为地基SAR高精度1维形变与3维形变实时测量算法。E-mail: yunkai_bit@foxmail.com

通讯作者:
邓云开 yunkai_bit@foxmail.com

中图分类号: TN95
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- 被引次数: 0
出版历程
- 收稿日期: 2018-12-17
- 修回日期: 2019-02-15
- 网络出版日期: 2019-02-28

Development State and Application Examples of Ground-based Differential Interferometric Radar

①.
Radar Research Lab, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
②.
Key Laboratory of Electronics and Information Technology in Satellite Navigation, Ministry of Education, Beijing Institute of Technology, Beijing 100081, China

Funds: The National Natural Science Foundation of China (61427802, 61601031), The National Science Fund for Distinguished Yong Scholars (61625103), The Foundation of Chang Jiang Scholars Programme (T2012122)

More Information

Corresponding author: DENG Yunkai, yunkai_bit@foxmail.com

摘要

摘要: 地基差分干涉雷达在形变监测领域已经得到了广泛的应用。该文首先概述了地基差分干涉雷达的主要类型，分为地基实孔径雷达和地基合成孔径雷达两类，并选择代表性系统介绍了工作原理及重要参数。然后以地基合成孔径雷达为例，介绍了现阶段差分干涉处理中的重要技术，包括差分干涉、PS点选择、大气相位补偿等。最后以3个应用实例，展现了地基差分干涉雷达，在露天开采边坡监测、山体滑坡监测和桥梁振动测量方面的应用。
- 地基雷达 /
- 差分干涉 /
- 形变测量 /
- 发展现状 /
- 应用实例
Abstract: Ground-Based Differential Interferometric Radars (GB-DInRads) have been widely applied to measure deformations. In this paper, the main types of GB-DInRads are summarized, including ground-based real aperture radar and Ground-Based Synthetic Aperture Radar (GB-SAR). The working principles and important parameters of some representative systems are introduced. Then, taking the GB-SAR as an example, the current key processing techniques are introduced, which mainly include differential interferometry, permanent scatterer selection, and atmospheric phase compensation. Lastly, three examples are presented to show the applications of GB-DInRad in deformation measurements. A Multiple-Input Multiple-Output (MIMO) radar was utilized to monitor an open-pit mine for about 11 days, and two regions with obvious deformation were found. In addition, a linear-scanning GB-SAR was utilized to monitor a mountain slope after severe landslide. The analysis result proved that rainfall could accelerate deformation. The feasibility of vibration measurement with the MIMO radar was also discussed in this paper.
- Ground-based radar /
- Differential interferometry /
- Deformation measurement /
- Development state /
- Application examples

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图 1 典型地基RAR

Figure 1. Typical GB-RAR systems

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图 2 典型直线扫描地基SAR

Figure 2. Typical linear-scanning GB-SAR systems

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图 3 典型弧线扫描地基SAR

Figure 3. Typical arc-scanning GB-SAR systems

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图 4 典型MIMO地基SAR

Figure 4. Typical MIMO GB-SAR systems

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图 5 部分地基RAR

Figure 5. Some GB-RAR systems

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图 6 地基SAR差分干涉处理流程

Figure 6. Differential interferometric scheme of GB-SAR

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图 7 差分干涉原理示意图

Figure 7. Schematic diagram of differential interferometry

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图 8 典型PS点选择结果

Figure 8. Typical PS selection results

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图 9 相位解缠结果

Figure 9. Phase unwrapping results

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图 10 干涉相位图

Figure 10. Phase interferogram

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图 11 实验信息

Figure 11. Experimental information

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图 12 MIMO雷达图像与干涉相位图

Figure 12. MIMO radar image and phase interferogram

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图 13 形变测量结果

Figure 13. Deformation measurement results

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图 14 形变分析结果

Figure 14. Deformation analysis results

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图 15 纳雍滑坡灾后现场监测照片

Figure 15. On-site monitoring photo after the Nayong landslide

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图 16 累积形变测量结果

Figure 16. Cumulative deformation measurements

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图 17 形变分析结果

Figure 17. Deformation analysis results

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图 18 实验信息

Figure 18. Experimental information

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图 19 振动分析结果

Figure 19. Vibration analysis results

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图 20 实验信息

Figure 20. Experimental information

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图 21 实验分析结果

Figure 21. Experimental analysis results

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表 1 直线扫描地基SAR参数表

Table 1. Parameters of linear-scanning GB-SAR

研究机构/公司	系统	波段	测量周期	空间分辨率(1 km处)	最远探测距离(km)
IDS公司 (意大利)	IBIS-FM	Ku	约3 min	0.5 m×4.4 m	4.5
JRC组织 (欧盟)	LiSA	Ku	约12 min	0.5 m×3.0 m	3
MetaSensing公司(荷兰)	FastGBSAR-S	Ku	10 s	0.5 m×4.8 m	4
UPC大学 (西班牙)	RiskSAR	X	约20 min	1.5 m×7.7 m	10
安科院 (中国)	S-SAR	Ku	<10 min	0.5 m×3.0 m	5
理工雷科公司 (中国)	边坡雷达	Ku	3～10 min	0.3 m×4.0 m	5
方向图公司 (中国)	LSA	Ku	4～10 min	0.2 m×5.4 m	5

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表 2 MIMO雷达参数表

Table 2. Parameters of the MIMO radar system

参数	数值	参数	数值
载频	16.2 GHz	发射信号时宽	0.1～0.5 ms
发射天线	16	发射信号带宽	400 MHz/1 GHz
接收天线	16	发射信号采样率	12.5 MHz/25.0 MHz
合成孔径长度	1.138 m	合成孔径采样点	256

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表 3 振动测量结果

Table 3. Vibrating measurement results

组号	振幅设定值(μm)	频率设定值(Hz)	频率测量值(Hz)	测量误差(Hz)	偏差比(%)
1	260	10	10.13	0.13	1.3
2	500	10	10.35	0.35	3.5
3	750	10	10.22	0.22	2.2
4	510	15	15.08	0.08	0.6
5	500	20	20.06	0.06	0.3
6	750	10	10.41	0.41	4.1
7	750	10	10.07	0.07	0.7

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参考文献(51)

[1]	刘传正. 中国崩塌滑坡泥石流灾害成因类型[J]. 地质评论, 2014, 60(4): 858–868. doi: 10.3969/j.issn.0371-5736.2014.04.015 LIU Chuanzheng. Genetic types of landslide and debris flow disasters in China[J]. Geological Review, 2014, 60(4): 858–868. doi: 10.3969/j.issn.0371-5736.2014.04.015
[2]	杨光华, 钟志辉, 张玉成, 等. 滑坡灾害的机制与力学特性分析[J]. 岩石力学与工程学报, 2016, 35(S2): 4009–4017. doi: 10.13722/j.cnki.jrme.2016.0804 YANG Guanghua, ZHONG Zhihui, ZHANG Yucheng, et al. Analysis of mechanism and mechanical characteristics of landslide disaster[J]. Chinese Journal of Rock Mechanics and Engineering, 2016, 35(S2): 4009–4017. doi: 10.13722/j.cnki.jrme.2016.0804
[3]	张德辉, 卢晓辉, 李天龙. GNSS实时形变监测系统在岩质高边坡中的应用[J]. 勘察科学技术, 2008(1): 36–38. doi: 10.3969/j.issn.1001-3946.2018.01.009 ZHANG Dehui, LU Xiaohui, and LI Tianlong. Application of GNSS surface displacement monitoring system in high rock slope[J]. Site Investigation Science and Technology, 2008(1): 36–38. doi: 10.3969/j.issn.1001-3946.2018.01.009
[4]	于欢欢, 徐亚富, 谢洪波. 基于三维激光扫描技术的边坡变形监测应用研究[J]. 中州煤炭, 2015(12): 111–113. doi: 10.3969/j.issn.1003-0506.2015.12.035 YU Huanhuan, XU Yafu, and XIE Hongbo. Application of slope deformation monitoring based on three-dimensional laser scanning technology[J]. Zhongzhou Coal, 2015(12): 111–113. doi: 10.3969/j.issn.1003-0506.2015.12.035
[5]	陈怡曲. 基于InSAR的形变监测技术研究[D]. [硕士论文], 电子科技大学, 2013. CHEN Yiqu. Deformation measurement techniques based on InSAR[D]. [Master dissertation], University of Electronic Science and Technology of China, 2013.
[6]	刘斌, 葛大庆, 李曼, 等. 地基合成孔径雷达干涉测量技术及其应用[J]. 国土资源遥感, 2017, 29(1): 1–6. doi: 10.6046/gtzyyg.2017.01.01 LIU Bin, GE Daqing, LI Man, et al. Ground-based interferometric synthetic aperture radar and its applications[J]. Remote Sensing for Land &Resources, 2017, 29(1): 1–6. doi: 10.6046/gtzyyg.2017.01.01
[7]	孙建勋, 郑会歌. 关于地基InSAR新技术及水利工程变形监测应用的研究[J]. 水利建设与管理, 2017, 37(11): 7–10. doi: 10.16616/j.cnki.11-4446/TV.2017.011.002 SUN Jianxun and ZHENG Huige. Research on application of foundation InSAR new technology and water conservancy engineering deformation monitoring[J]. Water Resources Development &Management, 2017, 37(11): 7–10. doi: 10.16616/j.cnki.11-4446/TV.2017.011.002
[8]	REEVES B, NOON D A, STICKLEY G F, et al. Slope stability radar for monitoring mine walls[C]. Proceedings of SPIE 4491, Subsurface and Surface Sensing Technologies and Applications III, San Diego, CA, United States, 2001: 57–67. doi: 10.1117/12.450188.
[9]	章亮, 任奋华, 王培涛, 等. 基于MSR300雷达监测的凹山采场降雨条件下的边坡变形及滑坡[J]. 工程科学学报, 2018, 40(4): 407–415. doi: 10.13374/j.issn2095-9389.2018.04.003 ZHANG Liang, REN Fenhua, WANG Peitao, et al. Investigation of deformation and failure in washan slope considering rainfall conditions based on MSR300 radar monitoring[J]. Chinese Journal of Engineering, 2018, 40(4): 407–415. doi: 10.13374/j.issn2095-9389.2018.04.003
[10]	WERNER C, WIESMANN A, STROZZI T, et al. The GPRI multi-mode differential interferometric radar for ground-based observations[C]. Proceedings of the 9th European Conference on Synthetic Aperture Radar, Nuremberg, Germany, 2012: 304–307.
[11]	ZENG Tao, MAO Cong, HU Cheng, et al. Ground-based SAR wide view angle full-field imaging algorithm based on keystone formatting[J]. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2016, 9(6): 2160–2170. doi: 10.1109/JSTARS.2016.2558578
[12]	RÖDELSPERGER S, LÄUFER G, GERSTENECKER C, et al. Monitoring of displacements with ground-based microwave interferometry: IBIS-S and IBIS-L[J]. Journal of Applied Geodesy, 2010, 4(1): 41–54. doi: 10.1515/JAG.2010.005
[13]	LEVA D, NICO G, TARCHI D, et al. Temporal analysis of a landslide by means of a ground-based SAR Interferometer[J]. IEEE Transactions on Geoscience and Remote Sensing, 2003, 41(4): 745–752. doi: 10.1109/TGRS.2003.808902
[14]	RÖDELSPERGER S and META A. MetaSensing’s FastGBSAR: Ground based radar for deformation monitoring[C]. Proceedings of SPIE 9243, SAR Image Analysis, Modeling, and Techniques XIV, Amsterdam, Netherlands, 2014. doi: 10.1117/12.2067243.
[15]	AGUASCA A, BROQUETAS A, MALLORQUI J, et al. A solid state L to X-band flexible ground-based SAR system for continuous monitoring applications[C]. Proceedings of IEEE International Geoscience and Remote Sensing Symposium, Anchorage, AK, USA, 2014. doi: 10.1109/IGARSS.2004.1368512.
[16]	林德才, 马海涛, 宋宝宏. 边坡雷达在滑坡应急救援行动中的应用[J]. 中国安全生产科学技术, 2016, 12(S1): 284–289. doi: 10.11731/j.issn.1673-193x.2016.S1.050 LIN Decai, MA Haitao, and SONG Baohong. Application of slope radar in emergency rescue of landslide[J]. Journal of Safety Science and Technology, 2016, 12(S1): 284–289. doi: 10.11731/j.issn.1673-193x.2016.S1.050
[17]	HU Cheng, ZHU Mao, ZENG Tao, et al. High-precision deformation monitoring algorithm for GBSAR system: Rail determination phase error compensation[J]. Science China Information Science, 2016, 59(8): 082307. doi: 10.1007/s11432-015-5446-z
[18]	路满, 宋红军, 罗运华. 基于调频连续波信号的圆弧式合成孔径雷达成像方法[J]. 雷达学报, 2016, 5(4): 425–433. doi: 10.12000/JR16007 LU Man, SONG Hongjun, and LUO Yunhua. Imaging algorithm for Arc synthetic aperture radar using frequency modulated continuous wave[J]. Journal of Radars, 2016, 5(4): 425–433. doi: 10.12000/JR16007
[19]	林赟, 谭维贤, 洪文, 等. 圆迹SAR极坐标格式算法研究[J]. 电子与信息学报, 2010, 32(12): 2802–2807. doi: 10.3724/SP.J.1146.2010.00003 LIN Yun, TAN Weixian, HONG Wen, et al. Polar format algorithm for circular synthetic aperture radar[J]. Journal of Electronics &Information Technology, 2010, 32(12): 2802–2807. doi: 10.3724/SP.J.1146.2010.00003
[20]	LEE H, LEE J H, KIM K E, et al. Development of a truck-mounted arc-scanning synthetic aperture radar[J]. IEEE Transactions on Geoscience and Remote Sensing, 2014, 52(5): 2773–2779. doi: 10.1109/TGRS.2013.2265700
[21]	VIVIANI F, MICHELINI A, MAYER L, et al. IBIS-ArcSAR: An innovative ground-based SAR system for slope monitoring[C]. Proceedings of 2018 IEEE International Geoscience and Remote Sensing Symposium, Valencia, Spain, 2018. doi: 10.1109/IGARSS.2018.8517702.
[22]	LUO Yunhua, SONG Hongjun, WANG R, et al. Arc FMCW SAR and applications in ground monitoring[J]. IEEE Transactions on Geoscience and Remote Sensing, 2014, 52(9): 5989–5998. doi: 10.1109/TGRS.2014.2325905
[23]	TARCHI D, OLIVERI F, and SAMMARTINO P F. MIMO radar and ground-based SAR imaging systems: Equivalent approaches for remote sensing[J]. IEEE Transactions on Geoscience and Remote Sensing, 2013, 51(1): 425–435. doi: 10.1109/TGRS.2012.2199120
[24]	HU C, WANG J, TIAN W, et al. Design and imaging of ground-based multiple-input multiple-output synthetic aperture radar (MIMO SAR) with non-collinear arrays[J]. Sensors, 2017, 17: 598. doi: 10.3390/s17030598
[25]	BROUSSOLLE J, KYOVTOROV V, BASSO M, et al. MELISSA, a new class of ground based InSAR system. An example of application in support to the Costa Concordia emergency[J]. ISPRS Journal of Photogrammetry and Remote Sensing, 2014, 91: 50–58. doi: 10.1016/j.isprsjprs.2014.02.003
[26]	乞耀龙, 王彦平, 李湖生, 等. 一种用于地基雷达数据成像处理的数字波束形成算法[J]. 信号处理, 2015, 31(10): 1313–1317. doi: 10.3969/j.issn.1003-0530.2015.10.014 QI Yaolong, WANG Yanping, LI Husheng, et al. Digital beam forming algorithm for ground-based radar imaging processing[J]. Journal of Signal Processing, 2015, 31(10): 1313–1317. doi: 10.3969/j.issn.1003-0530.2015.10.014
[27]	MONSERRAT O, CROSETTO M, and LUZI G. A review of ground-based SAR interferometry for deformation measurement[J]. ISPRS Journal of Photogrammetry and Remote Sensing, 2014, 93: 40–48. doi: 10.1016/j.isprsjprs.2014.04.001
[28]	CADUFF R, SCHLUNEGGER F, KOS A, et al. A review of terrestrial radar interferometry for measuring surface change in the geosciences[J]. Earth Surface Processes and Landforms, 2015, 40(2): 208–228. doi: 10.1002/esp.3656
[29]	朱茂. 基于动态PS的地基合成孔径雷达高精度形变测量技术研究[D]. [博士论文], 北京理工大学, 2016. ZHU Mao. High Precision Deformation measurement using ground based synthetic aperture radar (GBSAR) based on dynamic persistent scatter (PS) technique[D]. [Ph.D. dissertation], Beijing Institute of Technology, 2016.
[30]	FERRETTI A, PRATI C, and ROCCA F. Permanent scatterers in SAR interferometry[J]. IEEE Transactions on Geoscience and Remote Sensing, 2001, 39(1): 8–20. doi: 10.1109/36.898661
[31]	RÖDELSPERGER S. Real-time processing of ground based synthetic aperture radar (GB-SAR) measurements[D]. [Ph.D. dissertation], Technische Universitat Darmstadt, 2011.
[32]	周伟, 黄其欢, 张顺迎. 基于PS方法的地基SAR在大坝变形监测中的应用[J]. 勘察科学技术, 2016(1): 18–22. doi: 10.3969/j.issn.1001-3946.2016.01.005 ZHOU Wei, HUANG Qihuan, and ZHANG Shunying. Application of ground-based SAR in dam deformation monitoring based on PS method[J]. Site Investigation Science and Technology, 2016(1): 18–22. doi: 10.3969/j.issn.1001-3946.2016.01.005
[33]	CROSETTO M, MONSERRAT O, CUEVAS-GONZÁLEZ M, et al. Persistent scatterer interferometry: A review[J]. ISPRS Journal of Photogrammetry and Remote Sensing, 2016, 115: 78–89. doi: 10.1016/j.isprsjprs.2015.10.011
[34]	韩洁, 赖涛, 赵拥军, 等. 小数据集PS-DInSAR的PS点探测方法[J]. 信号处理, 2015, 31(6): 679–685. doi: 10.3969/j.issn.1003-0530.2015.06.007 HAN Jie, LAI Tao, ZHAO Yongjun, et al. Method on PS detection of small dataset PS-DInSAR[J]. Journal of Signal Processing, 2015, 31(6): 679–685. doi: 10.3969/j.issn.1003-0530.2015.06.007
[35]	COSTANTINI M and ROSEN P A. A generalized phase unwrapping approach for sparse data[C]. IEEE 1999 International Geoscience and Remote Sensing Symposium, Hamburg, Germany, 1999, 1: 267–269. doi: 10.1109/IGARSS.1999.773467.
[36]	OJHA C, MANUNTA M, PEPE A, et al. An innovative region growing algorithm based on Minimum Cost Flow approach for Phase Unwrapping of full-resolution differential interferograms[C]. 2012 IEEE International Geoscience and Remote Sensing Symposium, Munich, Germany, 2012: 5582–5585. doi: 10.1109/IGARSS.2012.6352054.
[37]	NOFERINI L, TAKAYAMA T, PIERACCINI M, et al. Analysis of ground-based SAR data with diverse temporal baselines[J]. IEEE Transactions on Geoscience and Remote Sensing, 2008, 46(6): 1614–1623. doi: 10.1109/TGRS.2008.916216
[38]	OSMANOĞLU B, DIXON T H, and WDOWINSKI S. Three-dimensional phase unwrapping for satellite radar interferometry, I: DEM generation[J]. IEEE Transactions on Geoscience and Remote Sensing, 2014, 52(2): 1059–1075. doi: 10.1109/TGRS.2013.2247043
[39]	张祥, 陆必应, 宋千. 地基SAR差分干涉测量大气扰动误差校正[J]. 雷达科学与技术, 2011, 9(6): 502–506. doi: 10.3969/j.issn.1672-2337.2011.06.004 ZHANG Xiang, LU Biying, and SONG Qian. Atmospheric disturbance correction in ground-based SAR differential interferometry[J]. Radar Science and Technology, 2011, 9(6): 502–506. doi: 10.3969/j.issn.1672-2337.2011.06.004
[40]	NOFERINI L, PIERACCINI M, MECATTI D, et al. Permanent scatterers analysis for atmospheric correction in ground-based SAR interferometry[J]. IEEE Transactions on Geoscience and Remote Sensing, 2005, 43(7): 1459–1471. doi: 10.1109/TGRS.2005.848707
[41]	HUANG Zengshu, SUN Jinping, LI Qing, et al. Time- and space-varying atmospheric phase correction in discontinuous ground-based synthetic aperture radar deformation monitoring[J]. Sensors, 2018, 18(11): 3883. doi: 10.3390/s18113883
[42]	IGLESIAS R, FABREGAS X, AGUASCA A, et al. Atmospheric phase screen compensation in ground-based SAR with a multiple-regression model over mountainous regions[J]. IEEE Transactions on Geoscience and Remote Sensing, 2014, 52(5): 2436–2449. doi: 10.1109/TGRS.2013.2261077
[43]	TAPETE D, CASAGLI N, LUZI G, et al. Integrating radar and laser-based remote sensing techniques for monitoring structural deformation of archaeological monuments[J]. Journal of Archaeological Science, 2013, 40(1): 176–189. doi: 10.1016/j.jas.2012.07.024
[44]	KOS A, STROZZI T, STOCKMANN R, et al. Detection and Characterization of Rock Slope Instabilities Using a Portable Radar Interferometer (GPRI)[M]. MARGOTTINI C, CANUTI P, SASSA K. Landslide Science and Practice. Berlin, Heidelberg: Springer, 2013. doi: 10.1007/978-3-642-31445-2_42.
[45]	刘作利, 刘景玉, 申修强, 等. 唐山马兰庄铁矿露天开采边坡变形监测的GB-InSAR技术[J]. 现代矿业, 2018(4): 165–170. doi: 10.3969/j.issn.1674-6082.2018.04.047 LIU Zuoli, LIU Jingyu, SHEN Xiuqiang, et al. Deformation monitoring of the open-pit slope of Malanshan iron mine in Tangshan City based on GB-InSAR[J]. Modern Mining, 2018(4): 165–170. doi: 10.3969/j.issn.1674-6082.2018.04.047
[46]	毛聪, 胡程, 曾涛, 等. 地基SAR子图相干合成快速成像算法[J]. 信号处理, 2015, 31(11): 1396–1403. doi: 10.3969/j.issn.1003-0530.2015.11.002 MAO Cong, HU Cheng, ZENG Tao, et al. Ground-based SAR fast imaging algorithm based on sub-image combination[J]. Journal of Signal Processing, 2015, 31(11): 1396–1403. doi: 10.3969/j.issn.1003-0530.2015.11.002
[47]	HU C, DENG Y, TIAN W, et al. A novel MIMO-SAR system applied for high-speed and high accuracy deformation measurement[C]. Proceedings of IET International Radar Conference 2018, Nanjing, China, 2018.
[48]	ZHU Mao, HU Cheng, ZENG Tao, et al. Experimental results and analysis for GBSAR deformation measurement[C]. IET International Radar Conference 2015, Hangzhou, China, 2015: 1–4. doi: 10.1049/cp.2015.1332.
[49]	MARCHISIO M, PIRODDI L, RANIERI G, et al. Comparison of natural and artificial forcing to study the dynamic behaviour of Bell Towers in low wind context by means of ground-based radar interferometry: The case of the Leaning Tower in Pisa[J]. Journal of Geophysics and Engineering, 2014, 11(5): 055004. doi: 10.1088/1742-2132/11/5/055004
[50]	LI Y, TIAN W, MEI H, et al. Weak vibration measurement technology and application based on FMCW radar system[C]. 2018 IET International Radar Conference, Nanjing, China, 2018.
[51]	MEI Hongyan, LI Yuqi, TIAN Weiming, et al. Weak vibration measurement based on MIMO imaging radar system[C]. Proceedings of 2018 China International SAR Symposium, Shanghai, China, 2018.