Development of the One Centimeter Accuracy Geoid Model of Latvia for GNSS Measurements

The mean sea surface topography of the Ionian and Adriatic Seas has been determined. This was based on six-months of Global Navigation Satellite System (GNSS) measurements which were performed on the Ionian Queen (a ship). The measurements were analyzed following a double-path methodology based on differential GNSS (D-GNSS) and precise point positioning (PPP) analysis. Numerical filtering techniques, multi-parametric accuracy analysis and a new technique for removing the meteorological tide factors were also used. Results were compared with the EGM96 geoid model. The calculated differences ranged between 0 and 48 cm. The error of the results was estimated to fall within 3.31 cm. The 3D image of the marine topography in the region shows a nearly constant slope of 4 cm/km in the N–S direction. Thus, the effectiveness of the approach “repeated GNSS measurements on the same route of a ship” developed in the context of “GNSS methods on floating means” has been demonstrated. The application of this approach using systematic multi-track recordings on conventional liner ships is very promising, as it may open possibilities for widespread use of the methodology across the world.

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On the determination of a locally optimized Ellipsoidal model of the Geoid surface in sea areas

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/906/1/012036 ◽

2021 ◽

Vol 906 (1) ◽

pp. 012036

Author(s):

Persephone Galani ◽

Sotiris Lycourghiotis ◽

Foteini Kariotou

Keyword(s):

Data Acquisition ◽

Sea Level ◽

Reference Ellipsoid ◽

Triaxial Ellipsoid ◽

Geoid Model ◽

Orthometric Heights ◽

The One ◽

Best Fit ◽

Local Geoid

Abstract Deriving a local geoid model has drawn much research interest in the last decade, in an endeavour to minimize the errors in orthometric heights calculations, inherited by the use of global geoid reference models. In most parts of the earth, the local geoid surface may be tens of meters away from the Global Reference biaxial Ellipsoid (WGS84), which create numerus problems in topographic, environmental and navigational applications. Several methods have been developed for optimizing the precision of the calculation of the geoid heights undulations and the accuracy of the corresponding orthometric heights calculations. The optimization refers either to the method used for data acquisition, or to the geometrical method used for the determination of the best fit local geoid model. In the present work, we focus on the reference ellipsoid used for the geometric and geoid heights determination and develop a method to provide the one that fits best to the local geoid surface. Moreover, we consider relatively small sea regions and near to coast areas, where the usual methods for data acquisition fail more or less, and we pay attention in two directions: To obtain accurate measured data and to have the best possible reference ellipsoid for the area at hand. In this due, we use the “GNSS-on-boat” methodology to obtain direct sea level data, which we induce in a Moore Penrose pseudoinverse procedure to calculate the best fit triaxial ellipsoid. This locally optimized reference ellipsoid minimizes the geometric heights in the region at hand. The method is applied in two closed sea areas in Greece, namely Corinthian and Patra’s gulf and also in four regions in the Ionian Sea, which exhibit significant geoid alterations. Taking into account all factors of uncertainty, the precision of the mean sea level surface, produced by the “GNSS on boat” methodology, had been estimated at 5.43 cm for the gulf of Patras, at 3.76 cm for the Corinthian gulf and at 3.31 for the Ionian and Adriatic Sea areas. The average difference of this surface and the local triaxial reference ellipsoid, calculated in this work, is found to be less than 15 cm, whereas the corresponding difference with respect to WGS84 is of the order of 30m.

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Construction of STHA-model of geometric geoid on the Lviv region area

Modern achievements of geodesic science and industry ◽

10.33841/1819-1339-2-42-49-56 ◽

2021 ◽

Vol 42 (II) ◽

pp. 49-56

Author(s):

F. ZABLOTSKYI ◽

◽

B. DZHUMAN ◽

Keyword(s):

Regularization Parameter ◽

Geometric Model ◽

Regional Model ◽

Practical Significance ◽

Independent Data ◽

Geoid Model ◽

Static Mode ◽

High System ◽

Rms Error ◽

Gnss Measurements

Nowadays there is a need to modernize the high system of Ukraine, which requires its integration in the European Vertical Reference System EVRS. In this regard there is also a need to build a regional model of the geoid on the territory of our country, which would be well consistent with the model of the European geoid EGG2015. To obtain the optimal model, it is necessary to use both gravimetric and geometric data. In this case, the model is called gravimetric-geometric. This approach is used both when building a model of the European geoid and when building geoid models on the territory of different European countries. Aim. The purpose of this work is to build a regional geometric STHA-model of the geoid on the Lviv region area and assess its accuracy. In the future it is planned to build a gravimetric STHA-model of the geoid in the same area and compare the results. Methods. To build a geometric STHA-model of the geoid on the Lviv region area, the heights of the geometric geoid, obtained from GNSS-observations at the points of SGN of I, II and III classes, were used. RMS error of determination of geodetic heights , obtained from GNSS leveling in static mode, did not exceed 15 mm. 205 values of the calculated heights of the geoid were used to build the geoid model. 8 values were not involved in the construction of the model, because they were used for an independent assessment of model accuracy. Results. The regional model of geoid within the “Remove–Compute–Restore” procedure with introduction of regularization parameter is obteined. RMS error of the obtained model, calculated on the basis of the data used in its construction, is 12 mm, and on other independent data is 25 mm. Scientific novelty and practical significance. For the first time STHA-functions were tested to build a regional geoid model. The geometric model of the geoid on the Lviv region are is calculated and the accuracy of the obtained model is estimated on the basis of dependent and independent data. The RMS error of the obtained model was about 2 cm, which corresponds to the accuracy of GNSS-measurements. The obtained model can be used as a transformation field on the Lviv region area.

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Enabling robust and accurate navigation for UAVs using real-time GNSS precise point positioning and IMU integration

The Aeronautical Journal ◽

10.1017/aer.2020.80 ◽

2020 ◽

Vol 125 (1283) ◽

pp. 87-108

Author(s):

C. Chi ◽

X. Zhan ◽

S. Wang ◽

Y. Zhai

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

Three Dimensional ◽

Coupled System ◽

Measurement Unit ◽

Satellite Geometry ◽

Tightly Coupled ◽

Point Positioning ◽

Gnss Measurements ◽

The One

ABSTRACTAccurate navigation is required in many Unmanned Aerial Vehicle (UAV) applications. In recent years, GNSS Precise Point Positioning (PPP) has been recognised as an efficient approach for providing precise positioning services. In contrast to the widely used Real-Time Kinematic (RTK), PPP is independent of reference stations, which greatly broadens its scope of application. However, the accuracy and reliability of PPP can be significantly decreased by poor GNSS satellite geometry and outage. In response, a real-time four-constellation GNSS PPP is applied to improve the geometry in this work, and PPP is tightly coupled with an Inertial Measurement Unit (IMU) to smooth the position and velocity output, thus improving the robustness of the navigation solution. Experimental flight tests are carried out using a UAV in an open-sky area, and GNSS-challenged environments are simulated. The results show that the four-constellation GNSS PPP/IMU integration reduces the Root-Mean-Square (RMS) Three-Dimensional (3D) positioning and velocity error by 76.4% and 67.1%, respectively, in open sky with respect to the one-GNSS PPP. Under scenarios where GNSS measurements are insufficient, the coupled system can still provide continuous solutions. Moreover, the coupled PPP/IMU system can also maintain the convergence of PPP during GNSS-challenged periods and can greatly shorten the re-convergence period of PPP when the UAV returns to the open sky.

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Extraction of geoid heights from shipborne GNSS measurements along the Weser River in northern Germany

Journal of Geodetic Science ◽

10.1515/jogs-2015-0014 ◽

2015 ◽

Vol 5 (1) ◽

Cited By ~ 4

Author(s):

D. Lavrov ◽

G. Even-Tzur ◽

J. Reinking

Keyword(s):

Measurement Data ◽

Geoid Height ◽

Theoretical Background ◽

Geoid Model ◽

Measuring Techniques ◽

Systematic Effects ◽

Gnss Measurements ◽

Accuracy Assessments

AbstractIn-land geoid models rely on several measuring techniques. The quality of those models is directly related to the spatial resolution of the measurement data. Occasionally, a local geoid model does not cover the coastal area at all and a local marine geoid simply does not exist. ShipborneGNSS measurementsmay provide away of overcoming this problem in coastal areas. However, several corrections to the raw measurements must be applied in order to account for systematic effects induced by ship dynamics and other static and dynamic impacts from tides, atmospheric pressure or wind stress. This paper presents the theoretical background for the method and the results of a case study in the estuary of the Weser River in Germany. A series of GNSS measurements were carried out aboard a ship and the approximate geoid height along the river was derived. For accuracy assessments of this method, the resultswere compared to the German Combined QuasiGeoid 2011 (GCG2011). The results are very promising and indicate the ability to extract geoid heights from shipborne GNSS measurements.

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Expansion and Improvement of the Israeli Geoid Model by Shipborne GNSS Measurements

Journal of Surveying Engineering ◽

10.1061/(asce)su.1943-5428.0000204 ◽

2017 ◽

Vol 143 (2) ◽

pp. 04016022 ◽

Cited By ~ 2

Author(s):

Dany Lavrov ◽

Gilad Even-Tzur ◽

Jörg Reinking

Keyword(s):

Geoid Model ◽

Gnss Measurements

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HIGH-PRECISION SATELLITE LEVELING AND INVESTIGATION OF THE LOCAL GEOID MODEL IN THE TERRITORY OF KASHKADARYA REGION

EPRA International Journal of Economic Growth and Environmental Issues ◽

10.36713/epra5788 ◽

2020 ◽

pp. 31-35

Author(s):

Fazilova D.Sh ◽

Magdiev H.N ◽

Halimov B.T

Keyword(s):

High Precision ◽

Reference System ◽

Reference Data ◽

Height Anomaly ◽

Geopotential Model ◽

Geoid Model ◽

Geopotential Models ◽

Normal Heights ◽

Gnss Measurements ◽

Local Geoid

In this paper, a study of the accuracy of obtaining normal heights using Global Geopotential Models EGM2008, EIGEN-6C4, GECO and GNSS measurements for the territory of the Kashkadarya region in Uzbekistan is carried out. The heights obtained by the classical leveling in Baltic reference system were used as reference data. EIGEN-6C4 and GECO models were recommended for definition a preliminary quasi  geoid model of the region. KEYWORDS: GNSS and classical leveling, Global Geopotential Model, height anomaly

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New geoid models computation in the Southeast part of Brazil

10.5194/egusphere-egu21-3284 ◽

2021 ◽

Author(s):

Valeria Silva ◽

Gabriel Guimarães ◽

Denizar Blitkow ◽

Ana Cristina Matos

Keyword(s):

Gravity Data ◽

Digital Terrain Model ◽

Minas Gerais ◽

Data Sets ◽

Geoid Model ◽

Terrain Model ◽

Paulo State ◽

Normal Heights ◽

Field Works ◽

Gnss Measurements

<p>In the last decade, big efforts have been undertaken in terms of gravity surveys in the Southeast part of Brazil. First of all, S&#227;o Paulo state has gravity data coverage quite completed in terms of 5&#8217; resolution. Second, in the last few years, some field works have been carried out in Minas Gerais state. The purpose of gravity densification is not only to improve the quality of geoid (quasi-geoid) models in Brazil, but also to contribute to the geodetic infrastructure, in particular, at the moment, for the establishment of the International Height Reference Frame, where two of six planned stations are located in the densification area. These efforts resulted in the computation of two quasi-geoid models in the Southeast region of Brazil. The decision is to compute a quasi-geoid instead of a geoid model, once since 2018, the Brazilian vertical system is based on normal heights. The Minas Gerais model was computed using Least Squares Collocation, via Fast Collocation. The spectral decomposition was employed in the technique for quasi-geoid model computation, where the reference field was represented by XGM2019 up to degree and order 200. The model was compared with GNSS/leveling in order to check the consistency of two different data sets. Two quasi-geoidal models for the S&#227;o Paulo state have been computed. Numerical integration through the Fast Fourier Transform (FFT) was used to perform the integral. The Molodensky gravity anomaly was determined in a 5&#8217; grid, reduced and restored using the Residual Terrain Model (RTM) technique and the XGM2019 with the degree and order 250 and 720. The validation for the S&#227;o Paulo quasi-geoid model is based on the GNSS measurements in the leveling network too.&#160; The Digital Terrain Model SRTM15 plus was used in the continent and the ocean areas in both states.</p>

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Note on Selection of Coordinate Systems for Geodynamics

International Astronomical Union Colloquium ◽

10.1017/s0252921100051174 ◽

1975 ◽

Vol 26 ◽

pp. 395-407

Author(s):

S. Henriksen

Keyword(s):

Sea Level ◽

The Other ◽

Coordinate Systems ◽

Mean Sea Level ◽

The Earth ◽

The One ◽

Static Systems ◽

Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

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Nucleation of Disorder in Fe3Al Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061574 ◽

1967 ◽

Vol 25 ◽

pp. 312-313

Author(s):

P. R. Swann ◽

W. R. Duff ◽

R. M. Fisher

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Annealing Temperature ◽

Antiphase Domain ◽

Effect Of Temperature ◽

Domain Structures ◽

Transmission Electron ◽

Domain Boundaries ◽

Higher Temperature ◽

The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

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