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See detailEstimating terrestrial water storage variations from GNSS vertical displacements in the Island of Haiti
Sauveur, Renaldo UL

Doctoral thesis (2023)

In the field of hydro-geodesy, ill-posed inverse problems are very common. Those problems need to be regularized to find a stabilized solution. Usually, to solve those problems, two regularization methods ... [more ▼]

In the field of hydro-geodesy, ill-posed inverse problems are very common. Those problems need to be regularized to find a stabilized solution. Usually, to solve those problems, two regularization methods are often used, Tikhonov’s regularization and Truncated Singular Value Decomposition (TSVD), with some common regularization parameter choice methods such as L-curve or General Cross Validation (GCV). This study aims to test the capacity of the Least Squares Collocation (LSC) method to estimate the terrestrial water storage variations as an original approach. First, for the forward model, we calculated the hydrological crustal loading deformation in the island of Haiti by convolving Farrell (1972) Green's function with the surface mass loading from the Global Land Data Assimilation (GLDAS). After, a dense synthetic Global Navigation Satellite System (GNSS) network is used with the LSC method to estimate the Terrestrial Water Storage (TWS) variations for the inverse problem. LSC is a natural way to stabilize an ill-posed inverse problem. Unlike Tikhonov’s or TSVD regularization method, LSC allows us to stabilize the inverse problem by including more physical information. The latter is introduced through a covariance function characterizing the observations, the parameters, and the functional link between them. One of the advantages of the LSC method is that it does not require any regularization parameter. First, we showed that, for the island of Haiti, the near field can extend until 24° around a GNSS station. Secondly, we proved that the hydrology-induced vertical deformation is part of the GNSS vertical displacement over the island. Finally, we demonstrated that the LSC may be used as a method to estimate TWS variations in dense GNSS network area. [less ▲]

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See detailA Precise Gravity Tide Model for Port-au-Prince in Haiti
Francis, Olivier UL; Guerrier, Kelly; Sauveur, Renaldo UL

Report (2023)

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See detailThe absolute Gravity Network of Haiti - Status Report 2021
Francis, Olivier UL; Sauveur, Renaldo UL; Beker, Neptune et al

Report (2021)

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See detailSNR-Based GNSS-R for Coastal Sea-Level Altimetry
Tabibi, Sajad UL; Sauveur, Renaldo UL; Guerrier, Kelly et al

in Geosciences (2021), 11(9 391),

Geodetic Global Navigation Satellite System reflectometry (GNSS-R) uses ground-based signals of opportunity to retrieve sea levels at an intermediate spatial scale. Geodetic GNSS-R is based on the ... [more ▼]

Geodetic Global Navigation Satellite System reflectometry (GNSS-R) uses ground-based signals of opportunity to retrieve sea levels at an intermediate spatial scale. Geodetic GNSS-R is based on the simultaneous reception of Line-of-Sight (LoS) and its coherent GNSS sea surface reflection (non-LOS) signals. The scope of this paper is to present geodetic GNSS-R applied to sea level altimetry. Signal-to-Noise Ratio (SNR) measurements from a Commercial Off-The-Shelf (COTS) geodetic-quality GNSS station at the Haiti Coast Guard Base in Port-au-Prince is used to retrieve sea levels in the International Terrestrial Reference Frame 2014 (ITRF2014). The GNSS-R sea levels are compared with those of the OTT Radar Level Sensor (RLS) installed vertically below the GNSS antenna. The Root-Mean-Square Error (RMSE) between the geodetic GNSS-R sea levels and OTT RLS records is 3.43 cm, with a correlation of 0.96. In addition, the complex differences between the OTT RLS records and 15-min GNSS-R sea levels using Global Positioning System (GPS) and Globalnaya Navigazionnaya Sputnikovaya Sistema (or Global Navigation Satellite System; GLONASS) signals for all the eight major tidal constituents are in mm-level agreement. Therefore, geodetic GNSS-R can be used as a complementary approach to the conventional method for sea level studies in a stable terrestrial reference frame. [less ▲]

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