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A method for retrieving soil moisture from GNSS-R by using experiment data
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作者 毛克彪 Ma Ying +4 位作者 Shen Xinyi Xia Lang Tian Shiying Han Jiaqi Liu Qing 《High Technology Letters》 EI CAS 2015年第2期219-223,共5页
Soil moisture is a key parameter in agricultural irrigation. The L band(1.58GHz) on board global position system (GPS) satellite is well suited for monitoring the change of soil moisture. In order to investigate t... Soil moisture is a key parameter in agricultural irrigation. The L band(1.58GHz) on board global position system (GPS) satellite is well suited for monitoring the change of soil moisture. In order to investigate the potential of retrieving soil moisture using the L-band GPS bistatic radar, this paper analyzed a retrieval method by using field experiment data. In order to investigate the relation- ship between the soil moisture ( corresponding roughly to the 0 - 5cm top soil layer) and the signal- to-noise ratio (PT-S-R) to the direct GPS signal-to-noise ratio (Pd_sNR), an experiment was conducted in Hulunber grassland of China in 2009 and 2011. Six field sites in the soil moisture experiment were utilized to analyze the relationship between soil moisture and the ratio of Pr-SNR to Pd-SN~ and the square of correlation coefficient was about 0.9 when the surface type was known and the elevation angle of the satellite ranged from 65 to 85 degrees approximately. The analysis shows that ratio of Pr-SNR to Pd-SNR can be used to monitor the soil moisture, because the ratio of Pr-SVR to Pd-SNR maxi- mized the elimination of the influence of different signals from different GPS satellites. The estimation accuracy could be improved if we make full use of the empirical knowledge on elevation angles of GPS satellites and ground roughness of different surface types. 展开更多
关键词 soil moisture global position system GPS) global navigation satellite system-reflection (gnss-r
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Differential Coherent Algorithm Based on Fast Navigation-Bit Correction for Airborne GNSS-R Software Receivers 被引量:3
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作者 Yiran Wang Bo Zhang Dingrong Shao 《Tsinghua Science and Technology》 SCIE EI CAS 2013年第1期88-99,共12页
Signals from the Global Navigation Satellite System (GNSS) scatter over the sea surface resulting in relatively low Signal-to-Noise Ratios (SNR). A differential coherent algorithm is given here to improve the SNR ... Signals from the Global Navigation Satellite System (GNSS) scatter over the sea surface resulting in relatively low Signal-to-Noise Ratios (SNR). A differential coherent algorithm is given here to improve the SNR and reduce the performance degradation due to the Squaring-Loss and the navigation-bit effect. The algorithm uses fast navigation-bit correction for Delay-Doppler Maps (DDM) in airborne Global Navigation Satellite Signal Reflectometry (GNSS-R) software receivers. The system model is introduced with an analysis of the statistical properties with simulations to support the theoretical analysis. Field experiments with real airborne receivers then demonstrate the effectiveness of this algorithm. Comparisons with test results show that this algorithm offers a significant SNR gain over conventional algorithms. 展开更多
关键词 satellite navigation signal processing global navigation satellite Signal Reflectometry (gnss-r Delay-Doppler maps differential coherence signal-to-noise ratio
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First spaceborne demonstration of BeiDou-3 signals for GNSS reflectometry from CYGNSS constellation 被引量:3
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作者 Weiqiang LI Estel CARDELLACH +2 位作者 Serni RIBO Antonio RIUS Bo ZHOU 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2021年第9期1-10,共10页
The full constellation of Chinese Global Navigation Satellite System(GNSS)Bei Dou-3 has been deployed completely and started fully operational service.In addition to providing global Positioning,Navigation and Timing(... The full constellation of Chinese Global Navigation Satellite System(GNSS)Bei Dou-3 has been deployed completely and started fully operational service.In addition to providing global Positioning,Navigation and Timing(PNT)services,the Bei Dou-3 satellites transmissions can also be used as the sources of illumination for Earth Observation(EO)with a bistatic radar configuration.This innovative EO concept,known as GNSS reflectometry(GNSS-R),allows to measure the Earth surface characteristics at high resolution via the reflected L-band radar signals collected by a constellation of small,low cost and low Earth orbiting satellites.For the first time in orbit,earth reflected Bei Dou-3 signal has been detected from the limited sets of raw data collected by the NASA’s Cyclone GNSS(CYGNSS)constellation.The feasibility of spaceborne Bei Dou-3 reflections on two typical applications,including sea surface wind and flooding inundation detection,has been demonstrated.The methodology and results give new strength to the prospect of new spaceborne GNSS-R instruments and missions,which can make multi-GNSS reflectometry observations available to better capture rapidly changing weather systems at better spatio-temporal scales. 展开更多
关键词 global navigation satellite System(GNSS) BeiDou-3 Small satellites Bistatic radar GNSS Reflectometry(gnss-r) CYGNSS Tropical cyclone Flood inundation
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TDS-1 GNSS reflectometry wind geophysical model function response to GPS block types 被引量:1
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作者 Fade Chen Xiaohong Zhang +3 位作者 Fei Guo Jiazhu Zheng Yang Nan Mohamed Freeshah 《Geo-Spatial Information Science》 SCIE EI CSCD 2022年第2期312-324,共13页
This paper presents the TDS-1 GNSS reflectometry wind Geophysical Model Function(GMF)response to GPS block types.The observables were extracted from Delay Doppler Maps(DDMs)after taking the receiver antenna gains effe... This paper presents the TDS-1 GNSS reflectometry wind Geophysical Model Function(GMF)response to GPS block types.The observables were extracted from Delay Doppler Maps(DDMs)after taking the receiver antenna gains effects and GNSS-R geometry effects into account.Since the DDM is affected by GPS EffectiveIsotropic Radiated Power(EIRP),we first investigate the sensitivity of observables to the GPS block.Additionally,the observables at high SNRs are more sensitive to wind speed,but the spatial coverage at high signal to noise ratios(SNRs)is lower,while DDMs at low SNRs have the opposite characteristics.To balance the accuracy and spatial coverage,the DDM datasets are divided into two parts:high SNR(>0 dB)and low SNR(>−10 dB and≤0 dB)to develop wind GMF.Then,the influences of GPS block on wind speed retrieval both at high and low SNR is analyzed.Results show that the block types have impacts on wind GMF and the use of a prior GPS block can contribute to a better wind speed retrieval both at high and low SNR.Compared with ASCAT,the Root Mean Square Error(RMSE)value of wind speed retrieval at high and low SNR are 2.19 m/s and 3.13 m/s,respectively,when all TDS data are processed without distinguishing GPS block types.However,if the TDS data are separately processed and used to develop wind GMF through different blocks,both the accuracy and correlation coefficient can be improved to some extent.Finally,the influence of significant height of the swell(Hs)on SNR observables is analyzed,and it is demonstrated that there is no obvious linear or nonlinear relationship between them. 展开更多
关键词 global navigation satellite system-reflectometry(gnss-r) Delay-Doppler Map(DDM) wind speed Geophysical Model Function(GMF) TechDemoSat-1(TDS-1) GPS block
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