Evaluation of the Land GNSS-Reflected DDM Coherence on Soil Moisture Estimation from CYGNSS Data

Dong, Zhounan; Jin, Shuanggen

doi:10.3390/rs13040570

Cited by 29 publications

(18 citation statements)

References 35 publications

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“…For the determination of peak region C peak , we referred to the DDMA (DDM average) method in sea-ice detection [43] to set a 5 × 3 delay-Doppler as the peak region, which is different from the 3 × 5 delay-Doppler region used by the DPSD method. The determination of 5 × 3 delay-Doppler region is based on the fact that coherent DDMs resemble the Woodward ambiguity function (WAF) without delay-Doppler spreading [44]. The WAF is defined as the DDM response induced by a point scatter and can be approximated by a delayspreading function and a Doppler-spreading function S as [27].…”

Section: New Coherence Detection Methodsmentioning

confidence: 99%

A New Coherence Detection Method for Mapping Inland Water Bodies Using CYGNSS Data

Wang

2022

Remote Sensing

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Inland water is an important part of the Earth’s water cycle. Mapping inland water is vital for understanding surface hydrology and climate change. Spaceborne global navigation satellite systems reflectometry (GNSS-R) has been proven to be an effective technique to detect inland water bodies. This paper proposes a new method to map inland water bodies using the delay-Doppler map (DDM) measurements provided by the GNSS-R platform Cyclone GNSS (CYGNSS). In this new method, we develop a refined power ratio to identify the coherence in DDM caused by the inland water. Processed with an image segmentation method, the refined power ratio is then applied to discriminate the permanent inland water bodies from the land. Using CYGNSS data over the Amazon Basin and the Congo Basin in 2020, we successfully generated water masks with a spatial resolution of 0.01°. Compared with the reference optical water masks, the overall detection accuracy in the Amazon Basin is 94.48% and the water detection accuracy is 92.23%, and the corresponding accuracies in the Congo Basin are 96.12% and 93.16%, respectively. Compared with the previous DDM power-spread detector (DPSD) method, the new method’s false alarms and misses in the Amazon Basin are reduced by 17.1% and 9.1%, respectively, while the false alarms and misses in the Congo Basin are reduced by 10.2% and 22%, respectively. Moreover, our method is proven to be useful for detecting short-term flood inundation.

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Section: New Coherence Detection Methodsmentioning

confidence: 99%

A New Coherence Detection Method for Mapping Inland Water Bodies Using CYGNSS Data

Wang

2022

Remote Sensing

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“…Better detection results were obtained with a higher sampling rate. Finally, [23,36,[47][48][49]. In general, for coherent returns to exist, the GPS signal has to be reflected over very large flat areas with the surface RMSE height lower than ~10 cm at L-Band as presented in [50].…”

Section: Land Surfacesmentioning

confidence: 99%

“…Figure 7. Example of CYGNSS-derived VOD by Xu et alSession 4: Land Processes II Several studies have demonstrated the importance of coherent scattering of the GPS reflected signal over land[23,36,[47][48][49]. In general, for coherent returns to exist, the GPS signal has to be reflected over very large flat areas with the surface RMSE height lower than ~10 cm at L-Band as presented in[50].…”

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confidence: 99%

The CYGNSS Mission: On-Going Science Team Investigations

et al. 2021

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In 2012, the National Aeronautics and Space Administration (NASA) selected the CYclone Global Navigation Satellite System (CYGNSS) mission coordinated by the University of Michigan (UM) as a low-cost and high-science Earth Venture Mission. The CYGNSS mission was originally proposed for ocean surface wind speed estimation over Tropical Cyclones (TCs) using Earth-reflected Global Positioning System (GPS) signals, as signals of opportunity. The orbital configuration of each CYGNSS satellite is a circular Low Earth Orbit (LEO) with an altitude ~520 km and an inclination angle of ~35°. Each single Delay Doppler Mapping Instrument (DDMI) aboard the eight CYGNSS microsatellites collects forward scattered signals along four specular directions (incidence angle of the incident wave equals incidence angle of the reflected wave) corresponding to four different transmitting GPS spacecrafts, simultaneously. As such, CYGNSS allows one to sample the Earth’s surface along 32 tracks simultaneously, within a wide range of the satellites’ elevation angles over tropical latitudes. Following the Earth Science Division 2020 Senior Review, NASA announced recently it is extending the CYGNSS mission through 30 September 2023. The extended CYGNSS mission phase is focused on both ocean and land surface scientific investigations. In addition to ocean surface wind speed estimation, CYGNSS has also shown a significant ability to retrieve several geophysical parameters over land surfaces, such as Soil Moisture Content (SMC), Above Ground Biomass (AGB), and surface water extent. The on-going science team investigations are presented in this article.

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“…Low Earth Orbit (LEO) satellite is a valuable platform for Earth observation due to the low altitude, short period, and rapid connection with the ground [ 1 ]. The observation data collected by the LEO satellite have been widely used in geosciences with a wide area coverage, such as crustal deformation [ 2 , 3 ], ocean altimetry [ 4 ], Earth gravity field recovery [ 5 , 6 ], space weather [ 7 , 8 ] and remote sensing [ 9 , 10 ]. To ensure successful scientific applications undertaken by the LEO satellite, the precise orbit determination (POD) for the LEO satellite is essential.…”

Section: Introductionmentioning

confidence: 99%

Undifferenced Kinematic Precise Orbit Determination of Swarm and GRACE-FO Satellites from GNSS Observations

Luo

Jin

Shi

2022

Sensors

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Low Earth Orbit (LEO) satellites can be used for remote sensing and gravity field recovery, while precise orbit determination (POD) is vital for LEO satellite applications. However, there are some systematic errors when using the LEO satellite orbits released by different agencies in multi-satellite-based applications, e.g., Swarm and Gravity Recovery and Climate Experiment-Follow-On (GRACE-FO), as different GNSS precise orbit and clock products are used as well as processing strategies and software. In this paper, we performed undifferenced kinematic PODs for Swarm and GRACE-FO satellites simultaneously over a total of 14 days by using consistent International Global Navigation Satellite System (GNSS) Service (IGS) precise orbit and clock products. The processing strategy based on an undifferenced ionosphere-free combination and a least squares method was applied for Swarm and GRACE-FO satellites. Furthermore, the quality control for the kinematic orbits was adopted to mitigate abrupt position offsets. Moreover, the accuracy of the kinematic orbits solution was evaluated by carrier phase residual analysis and Satellite Laser Ranging (SLR) observations, as well as comparison with official orbits. The results show that the kinematic orbits solution is better than 4 cm, according to the SLR validation. With quality control, the accuracy of the kinematic orbit solution is improved by 2.49 % for the Swarm-C satellite and 6.98 % for the GRACE-D satellite when compared with their precise orbits. By analyzing the accuracy of the undifferenced kinematic orbit solution, the reliability of the LEO orbit determination is presented in terms of processing strategies and quality control procedures.

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Evaluation of the Land GNSS-Reflected DDM Coherence on Soil Moisture Estimation from CYGNSS Data

Cited by 29 publications

References 35 publications

A New Coherence Detection Method for Mapping Inland Water Bodies Using CYGNSS Data

A New Coherence Detection Method for Mapping Inland Water Bodies Using CYGNSS Data

The CYGNSS Mission: On-Going Science Team Investigations

Undifferenced Kinematic Precise Orbit Determination of Swarm and GRACE-FO Satellites from GNSS Observations

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