Formal error assessment of geodetic mean dynamic topography at different spatial scales

Bai, Xixuan; Yan, Hui‐Juan; Zhu, Yongnan; Peng, Peng; Yan, Yi; Shen, Yingchun

doi:10.1016/j.jog.2020.101753

Cited by 3 publications

(2 citation statements)

References 31 publications

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“…The spatial resolution of sea surface height based on satellite altimetry data is about 20 − 30km, and that of geoid based on satellite gravity field is about 100 − 150km. The computational error in the geostrophic current due to measurement errors in sea surface height and geoid is about 5 − 20cm/s on a spatial scale of 100 − 150km [46], [47]. Due to the difficulty of obtaining a fine geostrophic current map that match the spatial resolution of the HF radar (2.5km), this article approximates that the geostrophic currents are consistent throughout the experimental sea area.…”

Section: Geostrophic Current Estimationmentioning

confidence: 88%

Wave Height Mapping From HF Radar-Measured Surface Current Data Based on a Cascaded LSTM Network

Tian,

Ma,

Yang

et al. 2024

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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High-frequency (HF) surface wave radar has been widely used for measuring sea surface current, but its accuracy and spatial coverage of sea wave measurement are limited. A wave height mapping method based on HF radar-measured surface currents is proposed in this article. The tidal currents are firstly estimated and subtracted from the radar-measured surface currents, and then the geostrophic currents are removed. The remaining currents, along with the wind directions, are used as input data to a cascaded long short-term memory (LSTM) network. This network contains two stages. The first stage divides the input data into two groups of high and low sea states, and the second stage performs wave height inversion for each group separately. By combining the inversion results of the two groups, wave height maps are obtained. The algorithm is verified using the experimental data from the southwestern Taiwan Strait. Using the numerical wave height fields as the ground truth, the proposed algorithm has a root-mean-square error (RMSE) of 0.35 m and a correlation coefficient (CC) of 0.90.

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Section: Geostrophic Current Estimationmentioning

confidence: 88%

Wave Height Mapping From HF Radar-Measured Surface Current Data Based on a Cascaded LSTM Network

Tian,

Ma,

Yang

et al. 2024

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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“…On the other hand, the error models of MSS and GGM could help to evaluate the formal errors of the MDT. However, the evaluation of the error characteristic of the MDT would still be hampered due to the filtering procedure; hence, methods that could evaluate errors of the MDT are presented in some studies (Bingham et al, 2014;Bai et al, 2020). For instance, Rio et al (2011)and Rio et al (2014) introduced an objective analysis method considering the variance-covariance and the correlation between observations for MDT modeling, which helps suppress the noise level in the MDT solution.…”

Section: Introductionmentioning

confidence: 99%

Spectrally Consistent Mean Dynamic Topography by Combining Mean Sea Surface and Global Geopotential Model Through a Least Squares-Based Approach

Shi

et al. 2022

Front. Earth Sci.

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The filtering procedure is usually mandatory for modeling mean dynamic topography (MDT) when a geodetic approach based on the Mean Sea Surface (MSS) and the Global Geopotential Model (GGM) is used. This is due to the inconsistent spectral contents between MSS and GGM. However, traditional isotropic filtering algorithms (e.g., Gaussian filter) consider neither the MDT locations nor their azimuth when smoothing the signal within the filtering radius. Hence, the isotropic filtering will attenuate the MDT signal near the current and filter the current signal into the surrounding ocean, which may lead to signal contamination and distortion. In this study, we set up a least squares-based (LS) approach to model MDT signal from the altimeter-derived MSS and geoid height using spherical harmonics from GGMs, where MDT is parameterized by Lagrange Basis Functions (LBFs). The design matrix is segmentally established, considering the error information of GGM in various spectral bands. Numerical experiments in the Gulf Stream show that applications of full error variance-covariance matrix or only diagonal error variance of GGM may have marginal effects on the MDT modeling. The MDT computed from this LS-based approach using the latest releases of Gravity Field and Steady-state Ocean Circulation Explorer (GOCE) geoid models, i.e., GO_CONS_GCF_2_DIR_R6 and Gravity Observation Combination 06s model (GOCO06s), have the best agreement with the comparison data, especially near the current region. Deduced geostrophic velocities based on the MDT solutions show that the LS-based approach recovers the current signal better than the Gaussian filtering by 1.8 cm/s. Estimated error map illustrates that errors are more concentrated near the coastal region.

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The establishment of a reference geodetic network made of closed polygonometric quadrangles and designated for landslide slopes

Simonyan

Volkov

2022

Vestnik MGSU

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Introduction. A reference geodetic network in the form of a closed polygonometric quadrangle is established at the Karamyshevsky landslide slope in Moscow for the purpose of repeated geodetic observations of landslide displacements. The purpose of the study is to show that the reference geodetic network in the form of closed polygonometric quadrangles can be implemented for landslide slopes along with other linear and angular methods. Materials and methods. Accurate or high-precision electronic total stations, such as Leica, Sokkia, Topcon, etc. are used to take field measurements. In this case, all four corners and all four sides are to be measured. There are three redundant measurements in this polygon of polygonometry to ensure the reliable control of the field work quality. It is advisable to equalize this polygon using the correlate type of the least squares method for the two reasons. First, to calculate the acceptable residuals, it is necessary to make an appropriate conditional equation, i.e. implement the most important and time-consuming part of the correlate method algorithm. Second, in the process of the algorithm implementation, the correlate method allows to obtain the inverse weights of equalized measurements, whose comparison with the inverse weights of unbalanced measurements provides a visual representation of the quality of the geometry of the designed network. Results. The mathematical processing of the results of geodetic measurements of the reference network in the form of closed polygonometric quadrangles using the method of least squares is quite complex and requires a computer technology and appropriate software. However if they are available, the problem is solved unambiguously and very accurately, which particularly important. Conclusions. The construction of reference geodetic networks in the form of closed polygonometric quadrangles for observing landslide displacements can be recommended for other landslide slopes.

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Formal error assessment of geodetic mean dynamic topography at different spatial scales

Cited by 3 publications

References 31 publications

Wave Height Mapping From HF Radar-Measured Surface Current Data Based on a Cascaded LSTM Network

Wave Height Mapping From HF Radar-Measured Surface Current Data Based on a Cascaded LSTM Network

Spectrally Consistent Mean Dynamic Topography by Combining Mean Sea Surface and Global Geopotential Model Through a Least Squares-Based Approach

The establishment of a reference geodetic network made of closed polygonometric quadrangles and designated for landslide slopes

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