scholarly journals Adaptive Smoothness Constraint Ionospheric Tomography Algorithm

Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2404 ◽  
Author(s):  
Debao Wen ◽  
Dengkui Mei ◽  
Yanan Du
Keyword(s):  
Three Dimensional ◽  
Satellite System ◽  
Geomagnetic Disturbance ◽  
Hunan Province ◽  
Ionospheric Tomography ◽  
Tomography System ◽  
Smoothness Constraint ◽  
Ill Posed ◽  
Ionospheric Imaging ◽  
Global Navigation Satellite

Ionospheric tomography reconstruction based on global navigation satellite system observations is usually an ill-posed problem. To resolve it, an adaptive smoothness constraint ionospheric tomography algorithm is proposed in this work. The new algorithm performs an adaptive adjustment for the constrained weight coefficients of the tomography system. The computational efficiency and the reconstructed quality of ionospheric imaging are improved by using the new algorithm. A numerical simulation experiment was conducted in order to validate the feasibility and superiority of the algorithm. The statistical results of the reconstructed errors and the comparisons of ionospheric profiles confirmed the superiority of the new algorithm. Finally, the new algorithm was successfully applied to reconstruct three-dimensional ionospheric images under geomagnetic quiet and geomagnetic disturbance conditions over Hunan province. The tomographic results are reasonable and consistent with the general behavior of the ionosphere. The positive and negative phase storm effects are found during geomagnetic storm occurrence.

scholarly journals Imaging the Three-Dimensional Ionospheric Structure with a Blob Basis Functional Ionospheric Tomography Model

Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2182
Author(s):  
Debao Wen ◽  
Dengkui Mei ◽  
Yanan Du
Keyword(s):  
Basis Function ◽  
Three Dimensional ◽  
Satellite System ◽  
Basis Functions ◽  
Ionospheric Electron Density ◽  
New Model ◽  
Ionospheric Tomography ◽  
Global Navigation Satellite ◽  
Simulation Scheme

A new ionospheric tomography model is presented in this work. In the new model, the traditional voxel basis function is replaced by the blob basis function. Due to the overlapping nature of their rotational symmetric basis functions, the new model introduces certain weighting from nearby tomographic spherical blobs. To confirm the feasibility of the new tomography model, a numerical simulation scheme is devised, and the simulation demonstrates that the reconstructed quality of the blob basis tomographic model is higher than that of the voxel basis tomographic model. Meanwhile, the variable blob radius is adopted in order to improve the efficiency of the new model. Finally, the new ionospheric tomography model is applied to reconstruct the temporal-spatial distribution of ionospheric electron density using actual global navigation satellite system observations. The comparisons between the tomographic profiles and those obtained from ionosonde data further demonstrate the reliability and the superiority of the new ionospheric tomography model.

scholarly journals Complementing regional ground GNSS-STEC computerized ionospheric tomography (CIT) with ionosonde data assimilation

GPS Solutions ◽  
2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Nicholas Ssessanga ◽  
Mamoru Yamamoto ◽  
Susumu Saito ◽  
Akinori Saito ◽  
Michi Nishioka
Keyword(s):  
Data Assimilation ◽  
Region Of Interest ◽  
Satellite System ◽  
Peak Height ◽  
Ionospheric Tomography ◽  
Occultation Data ◽  
Ionospheric Imaging ◽  
Computerized Ionospheric Tomography ◽  
Log Normal ◽  
Global Navigation Satellite

AbstractA near-real-time computerized ionospheric tomography (CIT) technique was developed over the East Asian sector to specify the 3-D electron density field. The technique is based on a plethora of Global Navigation Satellite System observables within the region of interest which is bounded horizontally 110°–160°E and 10°–60°N and extending from 80 to 25,000 km in altitude. Prior to deployment, studies validated the CIT results using ionosonde, middle-upper atmosphere radar and occultation data and found the technique to adequately reconstruct the regional ionosphere vertical structure. However, with room for improvement in estimating the peak height and avoiding physically unrealistic negative densities in the final solution, we present preliminary results from a technique that addresses these issues by incorporating CIT results into a data assimilation (DA) technique. The DA technique adds ionosonde bottomside measurements into CIT results, thereby improving the accuracy of the reconstructed bottomside 3-D structure. More specifically, on average CIT NmF2 and hmF2 improve by more than 60%. Further, during analysis, ionospheric electron densities are assumed to be better described by probability log-normal distribution, which introduces the positivity constraint that is mandatory in ionospheric imaging.

scholarly journals EGNOS Based APV Procedures Development Possibilities In The South-Eastern Part Of Poland

2014 ◽  
Vol 21 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Wojciech Z. Kaleta
Keyword(s):  
Three Dimensional ◽  
Dimensional Accuracy ◽  
Satellite System ◽  
Civil Aviation ◽  
The South ◽  
South Eastern ◽  
System Integrity ◽  
New Instrument ◽  
Global Navigation Satellite ◽  
First Time

AbstractOn 14th and 15th March 2011 for the first time approach with vertical guidance (APV-I) was conducted on Polish territory in Katowice, Kraków and Mielec. This was the milestone for GNSS (Global Navigation Satellite System) and Area Navigation (RNAV) use as a new instrument approach chance for NPA (Non-Precision Approach) and PA (Precision Approach) in Poland. The paper presents the experiment study of EGNOS SIS (Signal in Space) due to APV (Approach with Vertical Guidance) procedures development possibilities in the south-eastern part of Poland. Researches were conducted from January 2014 till June 2014 in three Polish cities: Warszawa, Kraków and Rzeszów. EGNOS as SBAS (Satellite Based Augmentation System) in according with ICAO's Annex 10 has to meet restrictive requirements for three dimensional accuracy, system integrity, availability and continuity of SIS. Because of ECAC (European Civil Aviation Conference) states to EGNOS coverage in the eastern part of Europe, location of mention above stations, shows real usefulness for SIS tests and evaluation of the results [EUROCONTROL, 2008].

scholarly journals Algorithm for Generating 3D Geometric Representation Based on Indoor Point Cloud Data

2020 ◽  
Vol 10 (22) ◽  
pp. 8073
Author(s):  
Min Woo Ryu ◽  
Sang Min Oh ◽  
Min Ju Kim ◽  
Hun Hee Cho ◽  
Chang Baek Son ◽  
...  
Keyword(s):  
Point Cloud ◽  
Indoor Environment ◽  
Three Dimensional ◽  
Satellite System ◽  
Normal Vector ◽  
Geometric Representation ◽  
Point Cloud Data ◽  
Cloud Data ◽  
Data Process ◽  
Global Navigation Satellite

This study proposes a new method to generate a three-dimensional (3D) geometric representation of an indoor environment by refining and processing an indoor point cloud data (PCD) captured through backpack laser scanners. The proposed algorithm comprises two parts to generate the 3D geometric representation: data refinement and data processing. In the refinement section, the inputted indoor PCD are roughly segmented by applying random sample consensus (RANSAC) to raw data based on an estimated normal vector. Next, the 3D geometric representation is generated by calculating and separating tangent points on segmented PCD. This study proposes a robust algorithm that utilizes the topological feature of the indoor PCD created by a hierarchical data process. The algorithm minimizes the size and the uncertainty of raw PCD caused by the absence of a global navigation satellite system and equipment errors. The result of this study shows that the indoor environment can be converted into 3D geometric representation by applying the proposed algorithm to the indoor PCD.

An Analysis of Alternatives for the COSMIC-2 Constellation in the Context of Global Observing System Simulation Experiments

2020 ◽  
Vol 35 (1) ◽  
pp. 51-66 ◽  
Author(s):  
L. Cucurull ◽  
M. J. Mueller
Keyword(s):  
System Simulation ◽  
Three Dimensional ◽  
Lower Troposphere ◽  
Weather Forecast ◽  
Satellite System ◽  
Forecast Skill ◽  
Added Value ◽  
Simulation Experiments ◽  
Global Navigation Satellite ◽  
The Impact

Abstract Observing system simulation experiments (OSSEs) were conducted to evaluate the potential impact of the six Global Navigation Satellite System (GNSS) radio occultation (RO) receiver satellites in equatorial orbit from the initially proposed Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) mission, known as COSMIC-2A. Furthermore, the added value of the high-inclination component of the proposed mission was investigated by considering a few alternative architecture designs, including the originally proposed polar constellation of six satellites (COSMIC-2B), a constellation with a reduced number of RO receiving satellites, and a constellation of six satellites but with fewer observations in the lower troposphere. The 2015 year version of the operational three-dimensional ensemble–variational data assimilation system of the National Centers for Environment Prediction (NCEP) was used to run the OSSEs. Observations were simulated and assimilated using the same methodology and their errors assumed uncorrelated. The largest benefit from the assimilation of COSMIC-2A, with denser equatorial coverage, was to improve tropical winds, and its impact was found to be overall neutral in the extratropics. When soundings from the high-inclination orbit were assimilated in addition to COSMIC-2A, positive benefits were found globally, confirming that a high-inclination orbit constellation of RO receiving satellites is necessary to improve weather forecast skill globally. The largest impact from reducing COSMIC-2B from six to four satellites was to slightly degrade weather forecast skill in the Northern Hemisphere extratropics. The impact of degrading COSMIC-2B to the COSMIC level of accuracy, in terms of penetration into the lower troposphere, was mostly neutral.

scholarly journals Hybrid 3D Models: When Geomatics Innovations Meet Extensive Built Heritage Complexes

2019 ◽  
Vol 8 (3) ◽  
pp. 124 ◽  
Author(s):  
Filiberto Chiabrando ◽  
Giulia Sammartano ◽  
Antonia Spanò ◽  
Alessandra Spreafico
Keyword(s):  
Three Dimensional ◽  
Laser Scanner ◽  
3D Models ◽  
Satellite System ◽  
3D Data ◽  
Mapping System ◽  
Aerial Vehicle ◽  
Mobile Mapping System ◽  
Global Navigation Satellite ◽  
Topographic Surveys

This article proposes the use of a multiscale and multisensor approach to collect and model three-dimensional (3D) data concerning wide and complex areas to obtain a variety of metric information in the same 3D archive, which is based on a single coordinate system. The employment of these 3D georeferenced products is multifaceted and the fusion or integration among different sensors’ data, scales, and resolutions is promising, and it could be useful in the generation of a model that could be defined as a hybrid. The correct geometry, accuracy, radiometry, and weight of the data models are hereby evaluated when comparing integrated processes and results from Terrestrial Laser Scanner (TLS), Mobile Mapping System (MMS), Unmanned Aerial Vehicle (UAV), and terrestrial photogrammetry, while using Total Station (TS) and Global Navigation Satellite System (GNSS) for topographic surveys. The entire analysis underlines the potentiality of the integration and fusion of different solutions and it is a crucial part of the ‘Torino 1911’ project whose main purpose is mapping and virtually reconstructing the 1911 Great Exhibition settled in the Valentino Park in Turin (Italy).

scholarly journals An improved pixel-based water vapor tomography model

2019 ◽  
Vol 37 (1) ◽  
pp. 89-100
Author(s):  
Yibin Yao ◽  
Linyang Xin ◽  
Qingzhi Zhao
Keyword(s):  
Water Vapor ◽  
Three Dimensional ◽  
Satellite System ◽  
Reference Station ◽  
Weather Forecasts ◽  
Satellite Positioning ◽  
Optimal Polynomial ◽  
Improved Model ◽  
Global Navigation Satellite ◽  
Gnss Data

Abstract. As an innovative use of Global Navigation Satellite System (GNSS), the GNSS water vapor tomography technique shows great potential in monitoring three-dimensional water vapor variation. Most of the previous studies employ the pixel-based method, i.e., dividing the troposphere space into finite voxels and considering water vapor in each voxel as constant. However, this method cannot reflect the variations in voxels and breaks the continuity of the troposphere. Moreover, in the pixel-based method, each voxel needs a parameter to represent the water vapor density, which means that huge numbers of parameters are needed to represent the water vapor field when the interested area is large and/or the expected resolution is high. In order to overcome the abovementioned problems, in this study, we propose an improved pixel-based water vapor tomography model, which uses layered optimal polynomial functions obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) by adaptive training for water vapor retrieval. Tomography experiments were carried out using the GNSS data collected from the Hong Kong Satellite Positioning Reference Station Network (SatRef) from 25 March to 25 April 2014 under different scenarios. The tomographic results are compared to the ECMWF data and validated by the radiosonde. Results show that the new model outperforms the traditional one by reducing the root-mean-square error (RMSE), and this improvement is more pronounced, at 5.88 % in voxels without the penetration of GNSS rays. The improved model also has advantages in more convenient expression.

scholarly journals The sensitivity of GNSS measurements in Fennoscandia to distinct three-dimensional upper-mantle structures

2013 ◽  
Vol 5 (2) ◽  
pp. 2389-2418
Author(s):  
H. Steffen ◽  
P. Wu
Keyword(s):  
Upper Mantle ◽  
Gravity Data ◽  
Three Dimensional ◽  
High Sensitivity ◽  
Element Model ◽  
Satellite System ◽  
Underlying Structure ◽  
Gnss Measurements ◽  
Global Navigation Satellite ◽  
Three Dimensional Finite Element

Abstract. We present the sensitivity of Global Navigation Satellite System (GNSS) measurements at selected GNSS stations used both in the EUREF Permanent Network as well as in the BIFROST project to distinct areas in a laterally heterogeneous upper mantle beneath Fennoscandia. We therefore use a three-dimensional finite element model for glacial isostatic adjustment (GIA) calculations. The underlying structure is based on the S20A seismic tomography model, whose shear-wave velocities have been transformed into a viscosity structure of the upper mantle. Lower mantle is not investigated as previous results showed negligible sensitivity of Fennoscandian GIA data to it. We subdivide the upper mantle in four layers with lateral viscosity structure. Areas with similar viscosity within a layer are combined to larger blocks. Further subdivision is made into areas inside and outside the formerly glaciated areas. This leads to about 20 differently shaped areas per layer. We then calculate the sensitivity kernels at 10 selected GNSS stations for all blocks in comparison to a well-fitting one-dimensional GIA model. We find that GNSS stations are most sensitive to mantle viscosity in the near surrounding of the station, i.e. in the nearest about 250 km, and only within the formerly glaciated area. This area can be enlarged up to 800 km when velocities of stations in the uplift center are investigated. There is no indication of sufficiently high sensitivity of all investigated GNSS stations to regions outside the glaciated area. We also note that in the first mantle layer (70–250 km depth) below the lithosphere, there is only small sensitivity to parts along the Norwegian coast. Most prominent features in the Fennoscandian upper mantle may be detected in the second (250–450 km depth) and third layer (450–550 km depth). In future investigations on the lateral viscosity structure using GNSS measurements one should only consider GNSS stations within the area of former glaciation. They can be further grouped to address certain areas. In a combination with other GIA data, e.g. relative sea-level and gravity data, it is then highly recommended to assign more weight on those GNSS results with high sensitivity in order to determine the viscosity of a certain region.

scholarly journals Assessment of global navigation satellite system (GNSS) radio occultation refractivity under heavy precipitation

2018 ◽  
Vol 18 (16) ◽  
pp. 11697-11708 ◽  
Author(s):  
Ramon Padullés ◽  
Estel Cardellach ◽  
Kuo-Nung Wang ◽  
Chi O. Ao ◽  
F. Joseph Turk ◽  
...  
Keyword(s):  
Radio Occultation ◽  
Three Dimensional ◽  
Heavy Precipitation ◽  
Satellite System ◽  
Specific Humidity ◽  
Positive Bias ◽  
Actual Measurement ◽  
Excess Phase ◽  
Global Navigation Satellite ◽  
Ray Paths

Abstract. A positive bias at heights between 3 and 8 km has been observed when comparing the radio-occultation (RO)-retrieved refractivity with that of meteorological analyses and reanalyses in cases where heavy precipitation is present. The effect of precipitation in RO retrievals has been investigated as a potential cause of the bias, using precipitation measurements interpolated into the actual three-dimensional RO ray paths to calculate the excess phase induced by precipitation. The study consisted of comparing the retrievals when such extra delay is removed from the actual measurement and when it is not. The results show how precipitation itself is not the cause of the positive bias. Instead, we show that the positive bias is linked to high specific-humidity conditions regardless of precipitation. This study also shows a regional dependence of the bias. Furthermore, different analyses and reanalyses show a disagreement under high specific-humidity conditions and, in consequence, heavy precipitation.

scholarly journals Three-dimensional morphology of equatorial plasma bubbles deduced from measurements onboard CHAMP

2015 ◽  
Vol 33 (1) ◽  
pp. 129-135 ◽  
Author(s):  
J. Park ◽  
H. Lühr ◽  
M. Noja
Keyword(s):  
Three Dimensional ◽  
Satellite System ◽  
Low Earth Orbit ◽  
Electron Content ◽  
Total Electron ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
Global Navigation Satellite ◽  
Plasma Depletion

Abstract. Total electron content (TEC) between Low-Earth-Orbit (LEO) satellites and the Global Navigation Satellite System (GNSS) satellites can be used to constrain the three-dimensional morphology of equatorial plasma bubbles (EPBs). In this study we investigate TEC measured onboard the Challenging Minisatellite Payload (CHAMP) from 2001 to 2005. We only use TEC data obtained when CHAMP passed through EPBs: that is, when in situ plasma density measurements at CHAMP altitude also show EPB signatures. The observed TEC gradient along the CHAMP track is strongest when the corresponding GNSS satellite is located equatorward and westward of CHAMP with elevation angles of about 40–60°. These elevation and azimuth angles are in agreement with the angles expected from the morphology of the plasma depletion shell proposed by Kil et al.(2009).

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