scholarly journals The Use of National CORS Networks for Determining Temporal Mass Variations within the Earth’s System and for Improving GRACE/GRACE-FO Solutions

2020 ◽  
Vol 12 (20) ◽  
pp. 3359
Author(s):  
Walyeldeen Godah ◽  
Jagat Dwipendra Ray ◽  
Malgorzata Szelachowska ◽  
Jan Krynski
Keyword(s):  
Geodetic Network ◽  
Satellite System ◽  
Temporal Variations ◽  
Global Scale ◽  
Satellite Mission ◽  
Equivalent Water Thickness ◽  
Grace Satellite ◽  
Gnss Data ◽  
Earth’S System

Temporal mass variations within the Earth’s system can be detected on a regional/global scale using GRACE (Gravity Recovery and Climate Experiment) and GRACE Follow-On (GRACE-FO) satellite missions’ data, while GNSS (Global Navigation Satellite System) data can be used to detect those variations on a local scale. The aim of this study is to investigate the usefulness of national GNSS CORS (Continuously Operating Reference Stations) networks for the determination of those temporal mass variations and for improving GRACE/GRACE-FO solutions. The area of Poland was chosen as a study area. Temporal variations of equivalent water thickness ΔEWT and vertical deformations of the Earth’s surface Δh were determined at the sites of the ASG-EUPOS (Active Geodetic Network of the European Position Determination System) CORS network using GRACE/GRACE-FO-based GGMs and GNSS data. Moreover, combined solutions of ΔEWT were developed by combining ΔEWT obtained from GNSS data with the corresponding ones determined from GRACE satellite mission data. Strong correlations (correlation coefficients ranging from 0.6 to 0.9) between detrended Δh determined from GRACE/GRACE-FO satellite mission data and the corresponding ones from GNSS data were observed at 93% of the GNSS stations investigated. Furthermore, for the determination of temporal mass variations, GNSS data from CORS network stations provide valuable information complementary to GRACE satellite mission data.

scholarly journals On the estimation of physical height changes using GRACE satellite mission data – A case study of Central Europe

2017 ◽  
Vol 66 (2) ◽  
pp. 211-226 ◽  
Author(s):  
Walyeldeen Godah ◽  
Małgorzata Szelachowska ◽  
Jan Krynski
Keyword(s):  
Central Europe ◽  
Decomposition Method ◽  
Temporal Variations ◽  
Satellite Mission ◽  
The Earth ◽  
Love Numbers ◽  
Grace Satellite ◽  
Physical Height ◽  
Earth’S System ◽  
Seasonal Decomposition

Abstract The dedicated gravity satellite missions, in particular the GRACE (Gravity Recovery and Climate Experiment) mission launched in 2002, provide unique data for studying temporal variations of mass distribution in the Earth’s system, and thereby, the geometry and the gravity fi eld changes of the Earth. The main objective of this contribution is to estimate physical height (e.g. the orthometric/normal height) changes over Central Europe using GRACE satellite mission data as well as to analyse them and model over the selected study area. Physical height changes were estimated from temporal variations of height anomalies and vertical displacements of the Earth surface being determined over the investigated area. The release 5 (RL05) GRACE-based global geopotential models as well as load Love numbers from the Preliminary Reference Earth Model (PREM) were used as input data. Analysis of the estimated physical height changes and their modelling were performed using two methods: the seasonal decomposition method and the PCA/ EOF (Principal Component Analysis/Empirical Orthogonal Function) method and the differences obtained were discussed. The main fi ndings reveal that physical height changes over the selected study area reach up to 22.8 mm. The obtained physical height changes can be modelled with an accuracy of 1.4 mm using the seasonal decomposition method.

scholarly journals Derivation of global ionospheric Sporadic E critical frequency ( f o Es) data from the amplitude variations in GPS/GNSS radio occultations

2020 ◽  
Vol 7 (7) ◽  
pp. 200320 ◽  
Author(s):  
Bingkun Yu ◽  
Christopher J. Scott ◽  
Xianghui Xue ◽  
Xinan Yue ◽  
Xiankang Dou
Keyword(s):  
Critical Frequency ◽  
Detection Threshold ◽  
Low Frequency ◽  
Satellite System ◽  
Global Scale ◽  
Satellite Mission ◽  
Frequency Detection ◽  
Sporadic E ◽  
The Uk ◽  
Global Navigation Satellite

The ionospheric sporadic E (Es) layer has a significant impact on the global positioning system (GPS)/global navigation satellite system (GNSS) signals. These influences on the GPS/GNSS signals can also be used to study the occurrence and characteristics of the Es layer on a global scale. In this paper, 5.8 million radio occultation (RO) profiles from the FORMOSAT-3/COSMIC satellite mission and ground-based observations of Es layers recorded by 25 ionospheric monitoring stations and held at the UK Solar System Data Centre at the Rutherford Appleton Laboratory and the Chinese Meridian Project were used to derive the hourly Es critical frequency ( f o Es) data. The global distribution of f o Es with a high spatial resolution shows a strong seasonal variation in f o Es with a summer maximum exceeding 4.0 MHz and a winter minimum between 2.0 and 2.5 MHz. The GPS/GNSS RO technique is an important tool that can provide global estimates of Es layers, augmenting the limited coverage and low-frequency detection threshold of ground-based instruments. Attention should be paid to small f o Es values from ionosondes near the instrumental detection limits corresponding to minimum frequencies in the range 1.28–1.60 MHz.

GNSS Sky Visibility Planning and Dilution of Precision Analysis for EOS Ground Station Selection for Nigeria Space Programme

2014 ◽  
Vol 1 (1) ◽  
pp. 70-93
Author(s):  
M. L. Ojigi ◽  
J. D. Dodo ◽  
Y. D. Opaluwa
Keyword(s):  
Geodetic Network ◽  
Satellite System ◽  
Global Scale ◽  
Precision Analysis ◽  
Observation Window ◽  
Dilution Of Precision ◽  
Ground Station ◽  
Analysis Technique ◽  
Total Control ◽  
Global Navigation Satellite

The establishment of Earth Observation Satellite (EOS) ground receiving stations in parts of Nigeria and other parts of the globe, similar to the Indian Remote Sensing (IRS) model will enhance global telecommand, precise EOS tracking, data transmission, and distribution of NigeriaSat data, which will enhance global-scale data awareness, usage and higher financial returns for Nigeria. This study, therefore, attempts the application of Global Navigation Satellite System (GNSS) sky visibility planning and dilution of precision analysis technique to select the optimal location for EOS ground station(s) in Nigeria. The Nigerian Geodetic Network (NigNet) GNSS Continuously Operating Reference Stations (CORS) RINEX data of February 2012 and Trimble Total Control (TTC) software were used for the determinations of the baselines and positions of the 11 available CORS. The technique of GNSS sky visibility planning and dilution of precision (DOP) was adopted because signals from satellites behave in a similar pattern in the atmosphere, so poor visibility in GNSS signals in a particular observation window translates relatively to poor orbit definition signal for an EOS. Based on Jon's rating of DOP values [1= ideal; 2-3 = excellent; 4-6 =good; 7-8= moderate; 9-20=fair; 21-50= poor)], the DOP values for the stations across Nigeria can be adjudged to range between excellent and good for ground receiving stations. However, the overall results showed that GEMB on ellipsoidal heights of 1795.7857m has the most suitable DOPs and sky visibility plan for ground receiving sites followed by CGG Toro (916.7853m) and RAMPOLY Maiduguri (702m). The sky visibility analysis showed the availability of an average of 9 GPS and 2 GLONASS constellation satellites to receivers at elevation angles of 10°-15° between 6:00hrs and 24:00hrs daily across Nigeria. The approach of OS ground receiving station suitability analysts demonstrated in this study is recommended for the Nigerian. La mise en place de stations de réception au sol par satellite d'observation de la Terre (EOS) dans certaines parties du Nigeria et d'autres parties du globe, similaires au modèle indien de télédétection (IRS) améliorera la télécommande mondiale, le suivi EOS précis, la transmission de données et la distribution des données NigeriaSat. , ce qui améliorera la connaissance et l'utilisation des données à l'échelle mondiale et des rendements financiers plus élevés pour le Nigéria. Cette étude tente donc d'appliquer la planification de la visibilité du ciel du système mondial de navigation par satellite (GNSS) et la dilution de la technique d'analyse de précision pour sélectionner l'emplacement optimal pour la ou les stations au sol EOS au Nigéria. Les données RINEX des stations de référence en fonctionnement continu (CORS) du réseau géodésique nigérian (NigNet) GNSS de février 2012 et le logiciel Trimble Total Control (TTC) ont été utilisés pour déterminer les lignes de base et les positions des 11 CORS disponibles. La technique de planification de la visibilité du ciel GNSS et de dilution de la précision (DOP) a été adoptée car les signaux des satellites se comportent de manière similaire dans l'atmosphère, de sorte qu'une mauvaise visibilité des signaux GNSS dans une fenêtre d'observation particulière se traduit par un signal de définition d'orbite médiocre pour un EOS. . Basé sur l'évaluation des valeurs DOP de Jon [1 = idéal ; 2-3 = excellent ; 4-6 = bon ; 7-8= modéré ; 9-20=juste ; 21-50 = pauvre)], les valeurs DOP pour les stations à travers le Nigeria peuvent être estimées entre excellentes et bonnes pour les stations de réception au sol. Cependant, les résultats globaux ont montré que GEMB sur des hauteurs ellipsoïdales de 1795,7857m a les DOP et le plan de visibilité du ciel les plus appropriés pour les sites de réception au sol, suivis de CGG Toro (916,7853m) et RAMPOLY Maiduguri (702m). L'analyse de la visibilité du ciel a montré la disponibilité d'une moyenne de 9 satellites GPS et 2 satellites de la constellation GLONASS aux récepteurs à des angles d'élévation de 10° à 15° entre 6h00 et 24h00 tous les jours à travers le Nigeria. L'approche des analystes de l'adéquation des stations de réception au sol OS démontrée dans cette étude est recommandée pour le Nigérian.

Testing Correlation between Vertical Crustal Movements and Geoid Uplift for North Eastern Polish Border Areas

2017 ◽  
Author(s):  
Kamil Kowalczyk ◽  
Joanna Kuczynska-Siehien
Keyword(s):  
Temporal Variations ◽  
Geoid Height ◽  
Satellite Observations ◽  
Satellite Mission ◽  
Crustal Movements ◽  
North Eastern ◽  
Long Time ◽  
Grace Satellite ◽  
Border Areas ◽  
Vertical Crustal Movements

Long time span of observations from GNSS permanent stations can be used in the development of models of vertical crustal movements. The absolute vertical crustal movement related to the ellipsoid consists of the observed movement with relation to the mean sea level, the eustatic movement and the geoid uplift. The geoid uplift can be determined from GRACE satellite mission observations. The calculated parameters can be compared with the theoretical ones. The aim of this study is to check the correlation between vertical crustal movements and a geoid height variations determined from satellite data. GNSS data, levelling data and satellite observations for north eastern Polish border areas were used as a case study. Temporal variations of geoid were calculated based on the geopotential models from GRACE satellite observations. The obtained results give an overview of a possibility of the proposed method usage.

scholarly journals Assessment of Temporal Variations of Orthometric/Normal Heights Induced by Hydrological Mass Variations over Large River Basins Using GRACE Mission Data

2020 ◽  
Vol 12 (18) ◽  
pp. 3070
Author(s):  
Walyeldeen Godah ◽  
Malgorzata Szelachowska ◽  
Jan Krynski ◽  
Jagat Dwipendra Ray
Keyword(s):  
River Basin ◽  
Amazon Basin ◽  
Principal Component ◽  
River Basins ◽  
Temporal Variations ◽  
Large River ◽  
Satellite Mission ◽  
Equivalent Water Thickness ◽  
Normal Heights ◽  
Large River Basins

Almost half of the Earth’s land is covered by large river basins. Temporal variations of hydrological masses induce time-varying gravitational potential and temporal mass loading that deforms the Earth’s surface. These phenomena cause temporal variations of geoid/quasigeoid and ellipsoidal heights that result in temporal variations of orthometric/normal heights ΔH/ΔH*. The aim of this research is to assess ΔH/ΔH* induced by hydrological masses over large river basins using the Gravity Recovery and Climate Experiment (GRACE) satellite mission data. The results obtained reveal that for the river basin of a strong hydrological signal, ΔH/ΔH* reach 8 cm. These ΔH/ΔH* would be needed to reliably determine accurate orthometric/normal heights. The ΔH/ΔH* do not exceed ±1 cm in the case of the river basin of the weak hydrological signal. The relation between hydrological mass changes and ΔH/ΔH* was investigated. Correlations between ΔH/ΔH* and temporal variations of equivalent water thickness were observed in 87% of river basins subareas out of which 45% exhibit strong correlations. The ΔH/ΔH* determined over two river basins that characterize with the strongest and weakest temporal variations were analysed using the Principal Component Analysis method. The results obtained reveal that ΔH/ΔH* in subareas of the same river basin can significantly differ (e.g., ±2 cm in the Amazon basin) from each other, and are strongly associated with different spatio-temporal patterns of the entire river basin.

Hydrogeology correction in the gravitational field from satellite data

2018 ◽  
Vol 931 (1) ◽  
pp. 2-7
Author(s):  
V.D. Jushkin ◽  
L.V. Zotov ◽  
O.A. Khrapenko
Keyword(s):  
Gravitational Field ◽  
Oil And Gas ◽  
Repeated Measurements ◽  
Geological Factors ◽  
Grace Satellite ◽  
Gas Pumping ◽  
Acceleration Of Gravity ◽  
Determination Of Parameters ◽  
Gravity Acceleration

The results of repeated measurements of the acceleration of gravity by the Russian absolute ballistic field gravimeter GABL-M on points of oil and gas deposits in the permafrost over a five year period are presented. The changes of gravity acceleration by the absolute gravimeter and GRACE satellite were compared. The results of comparisons of differences gravity acceleration by ballistic gravimeter GABL-M and relative Canadian gravimeters CG5 were [i]shown. The errors in determination of parameters of the gravitational field ballistic gravimeter GABL-M and CG5 gravimeters group were presented. The method of measurement with the gravimeter GABL-M and the method of determining the vertical gradients relative CG5 gravity meters was described. The necessity of introducing corrections of hydrogeology is caused by influence of hydro geological factors on the gravitational field in the permafrost. They are comparable with the values of the field change in the result of gas pumping.

scholarly journals Functional model modification of precise point positioning considering the time-varying code biases of a receiver

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Baocheng Zhang ◽  
Chuanbao Zhao ◽  
Robert Odolinski ◽  
Teng Liu
Keyword(s):  
Precise Point Positioning ◽  
Functional Model ◽  
Geodetic Network ◽  
Temporal Variations ◽  
Gps Data ◽  
Electron Content ◽  
Time Varying ◽  
Dual Frequency ◽  
Total Electron ◽  
Point Positioning

AbstractPrecise Point Positioning (PPP), initially developed for the analysis of the Global Positing System (GPS) data from a large geodetic network, gradually becomes an effective tool for positioning, timing, remote sensing of atmospheric water vapor, and monitoring of Earth’s ionospheric Total Electron Content (TEC). The previous studies implicitly assumed that the receiver code biases stay constant over time in formulating the functional model of PPP. In this contribution, it is shown this assumption is not always valid and can lead to the degradation of PPP performance, especially for Slant TEC (STEC) retrieval and timing. For this reason, the PPP functional model is modified by taking into account the time-varying receiver code biases of the two frequencies. It is different from the Modified Carrier-to-Code Leveling (MCCL) method which can only obtain the variations of Receiver Differential Code Biases (RDCBs), i.e., the difference between the two frequencies’ code biases. In the Modified PPP (MPPP) model, the temporal variations of the receiver code biases become estimable and their adverse impacts on PPP parameters, such as ambiguity parameters, receiver clock offsets, and ionospheric delays, are mitigated. This is confirmed by undertaking numerical tests based on the real dual-frequency GPS data from a set of global continuously operating reference stations. The results imply that the variations of receiver code biases exhibit a correlation with the ambient temperature. With the modified functional model, an improvement by 42% to 96% is achieved in the Differences of STEC (DSTEC) compared to the original PPP model with regard to the reference values of those derived from the Geometry-Free (GF) carrier phase observations. The medium and long term (1 × 104 to 1.5 × 104 s) frequency stability of receiver clocks are also significantly improved.

scholarly journals From GPS Receiver to GNSS Reflectometry Payload Development for the Triton Satellite Mission

2021 ◽  
Vol 13 (5) ◽  
pp. 999
Author(s):  
Yung-Fu Tsai ◽  
Wen-Hao Yeh ◽  
Jyh-Ching Juang ◽  
Dian-Syuan Yang ◽  
Chen-Tsung Lin
Keyword(s):  
Satellite System ◽  
Low Earth Orbit ◽  
Export Control ◽  
Navigation Systems ◽  
Gps Receiver ◽  
Design Development ◽  
Satellite Mission ◽  
Essential Components ◽  
Gnss Reflectometry ◽  
Global Navigation Satellite

The global positioning system (GPS) receiver has been one of the most important navigation systems for more than two decades. Although the GPS system was originally designed for near-Earth navigation, currently it is widely used in highly dynamic environments (such as low Earth orbit (LEO)). A space-capable GPS receiver (GPSR) is capable of providing timing and navigation information for spacecraft to determine the orbit and synchronize the onboard timing; therefore, it is one of the essential components of modern spacecraft. However, a space-grade GPSR is technology-sensitive and under export control. In order to overcome export control, the National Space Organization (NSPO) in Taiwan completed the development of a self-reliant space-grade GPSR in 2014. The NSPO GPSR, built in-house, has passed its qualification tests and is ready to fly onboard the Triton satellite. In addition to providing navigation, the GPS/global navigation satellite system (GNSS) is facilitated to many remote sensing missions, such as GNSS radio occultation (GNSS-RO) and GNSS reflectometry (GNSS-R). Based on the design of the NSPO GPSR, the NSPO is actively engaged in the development of the Triton program (a GNSS reflectometry mission). In a GNSS-R mission, the reflected signals are processed to form delay Doppler maps (DDMs) so that various properties (including ocean surface roughness, vegetation, soil moisture, and so on) can be retrieved. This paper describes not only the development of the NSPO GPSR but also the design, development, and special features of the Triton’s GNSS-R mission. Moreover, in order to verify the NSPO GNSS-R receiver, ground/flight tests are deemed essential. Then, data analyses of the airborne GNSS-R tests are presented in this paper.

Study the Effect of Radio Interference of the EHV Transmission Line on GNSS Signals

2013 ◽  
Vol 805-806 ◽  
pp. 851-854
Author(s):  
Zhi Ge Jia ◽  
Zhao Sheng Nie ◽  
Wei Wang ◽  
Xiao Guan ◽  
Di Jin Wang
Keyword(s):  
Transmission Line ◽  
Transmission Lines ◽  
Internal Noise ◽  
Field Testing ◽  
Satellite System ◽  
Field Analysis ◽  
Radio Interference ◽  
Gnss Receiver ◽  
Global Navigation Satellite ◽  
Gnss Data

This work describes the field testing process of Global Navigation Satellite System (GNSS) receiver under 220KV, 500KV UHV transmission line and standard calibration field. Analysis for GNSS data results shows that the radio interference generated by EHV transmission lines have no effect on GNSS receiver internal noise levels and valid GNSS observation rate. Within 50 meters of the EHV transmission lines, the multi-path effects (mp1 and mp2 value) significantly exceeded the normal range and becomes larger with the increase of the voltage .outside 50 meters of the EHV transmission line, the multi-path effects have almost no effect on the high-precision GNSS observations.

Geodetic observations for constraining mantle processes in Antarctica

2021 ◽  
pp. M56-2021-22
Author(s):  
Mirko Scheinert ◽  
Olga Engels ◽  
Ernst J. O. Schrama ◽  
Wouter van der Wal ◽  
Martin Horwath
Keyword(s):  
Data Sets ◽  
Satellite Mission ◽  
Amundsen Sea ◽  
Isostatic Adjustment ◽  
Geodynamic Processes ◽  
Grace Satellite ◽  
Mantle Processes ◽  
Gnss Measurements ◽  
The Individual ◽  
Seismic Deformation

AbstractGeodynamic processes in Antarctica such as glacial isostatic adjustment (GIA) and post-seismic deformation are measured by geodetic observations such as GNSS and satellite gravimetry. GNSS measurements have been comprising continuous measurements as well as episodic measurements since the mid-1990s. The estimated velocities typically reach an accuracy of 1 mm/a for horizontal and 2 mm/a for vertical velocities. However, the elastic deformation due to present-day ice-load change needs to be considered accordingly.Space gravimetry derives mass changes from small variations in the inter-satellite distance of a pair of satellites, starting with the GRACE satellite mission in 2002 and continuing with the GRACE-FO mission launched in 2018. The spatial resolution of the measurements is low (about 300 km) but the measurement error is homogeneous across Antarctica. The estimated trends contain signals from ice mass change, local and global GIA signal. To combine the strengths of the individual data sets statistical combinations of GNSS, GRACE and satellite altimetry data have been developed. These combinations rely on realistic error estimates and assumptions of snow density. Nevertheless, they capture signal that is missing from geodynamic forward models such as the large uplift in the Amundsen Sea sector due to low-viscous response to century-scale ice-mass changes.

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