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

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

Accuracy Assessment of Recent High-Degree Global Geopotential Models Using Geodetic Control Points and Terrestrial Gravity Data in Turkey

2021 ◽  
Author(s):  
Muhammed Raşit Çevikalp ◽  
Bihter Erol ◽  
Bilal Mutlu ◽  
Serdar Erol
Keyword(s):  
Gravity Data ◽  
Geopotential Model ◽  
Geoid Model ◽  
Terrestrial Gravity ◽  
Practical Applications ◽  
Geopotential Models ◽  
Vertical Datum ◽  
Height System ◽  
Orthometric Heights ◽  
Height System Unification

<p>The maintenance of leveling benchmark is both laborious and costly due to distortions caused by geodynamic activities and local deformations. It is necessary to realize geoid-based vertical datum, which also enables calculation from ellipsoidal heights obtained from GNSS to orthometric heights that have physical meaning. It can be considered as an important step for height system unification as it eliminates the problems stem from the conventional vertical datum. The ongoing height modernization efforts in Turkey focus to improve quality and coverage of the gravity data, eliminate errors in existing terrestrial gravity measurements in order to achieve a precise geoid model. Accuracy of the geopotential model is crucial while realizing a geoid model based vertical datum as well as unifying the regional height systems with the International Heights Reference System. In this point of view, we assessed the accuracies of recently released global geopotential models including XGM2019e_2159, GECO, EIGEN-6C4, EGM2008, SGG-UGM-1, EIGEN-6C3stat, and EIGEN-6C2 using high order GNSS/leveling control benchmarks and terrestrial gravity data in Turkey. The reason for choosing these models in the validations is their relatively higher spatial resolutions and improved accuracies compared to other GGMs in published validation results with globally distributed terrestrial data. The GNSS/leveling data used in validations include high accuracy GNSS coordinates in ITRF datum with co-located Helmert orthometric heights in regional vertical datum. 100 benchmarks are homogeneously distributed in the country with the benchmarks along the coastlines. In addition, the terrestrial gravity anomalies with 5 arc-minute resolution were also used in the tests. In order to have comparable results, residual terrain effect has been restored to the GGM derived parameters. Numerical tests revealed significant differences in accuracies of the tested GGMs. The most accurate GGM has the comparable performance with official regional geoid model solutions in Turkey. The drawn results in the study were interpreted and discussed from practical applications and height system unification points in conclusion.</p>

The digital zenith camera as an additional technique for quasi-geoid model determination of Latvia

2020 ◽  
Author(s):  
Katerina Morozova ◽  
Gunars Silabriedis ◽  
Ansis Zarins ◽  
Janis Balodis ◽  
Reiner Jaeger
Keyword(s):  
Geological Structure ◽  
Geopotential Model ◽  
Parametric Modelling ◽  
Vertical Deflection ◽  
Geoid Model ◽  
Star Catalog ◽  
Geopotential Models ◽  
Model Determination ◽  
The University

<p>The digital zenith camera VESTA (VErtical by STArs) was designed by the Institute of Geodesy and Geoinformatics (GGI) of the University of Latvia and completed in 2016. By 2020 more than 400 terrestrial vertical deflection measurements were observed in the territory of Latvia. These observations were post-processed by the GGI developed software and the accuracy was evaluated at 0.1 arc seconds. In 2019 two new cameras have been developed, which will be used in future projects, e.g., in determination of properties of local geological structure or Earth crust movement monitoring. Measurement control software corrections and complements, data processing improvements and automation and transition to GAIA data release 2 star catalog were done. The accuracy of the measurements of improved camera was evaluated at 0.05 arc seconds.</p><p>Terrestrial vertical deflection observations were compared with global geopotential models, e.g. GGM+ and EGM2008. The results show a better correspondence with GGM+ model by evaluating the standard deviation: 0.314 and 0.307 arc seconds for ξ and η components respectively in comparison to 0.346 and 0.358 arc seconds for ξ and η components for EGM2008 model. The comparisons of average and minimum/maximum differences are introduced in this study for better evaluation of the results. Moreover, vertical deflections have been used as additional terrestrial data in DFHRS (Digital Finite-element Height Reference Surface) software v. 4.3 in combination with GNSS/levelling data (B, L, hH) and global geopotential model EGM2008 for gravity field and quasi-geoid improvement (www.dfhbf.de). This approach is based on parametric modelling and computation of height reference surfaces (HRS) from geometric and physical observation components in a hybrid adjustment approach. The results of the computed quasi-geoid models using different types of data are introduced in this research, representing several solutions, as well as these solutions are compared with the national quasi-geoid model LV’14.</p>

scholarly journals An analysis of methods for gravity determination and their utilization for the calculation of geopotential numbers in the Slovak national levelling network

2016 ◽  
Vol 46 (3) ◽  
pp. 179-202 ◽  
Author(s):  
Miroslava Majkráková ◽  
Juraj Papčo ◽  
Pavol Zahorec ◽  
Branislav Droščák ◽  
Ján Mikuška ◽  
...  
Keyword(s):  
Reference System ◽  
Slovak Republic ◽  
Bouguer Anomaly ◽  
Geopotential Model ◽  
Bouguer Anomalies ◽  
Global Geopotential Model ◽  
Terrain Model ◽  
The Core ◽  
Normal Heights

Abstract The vertical reference system in the Slovak Republic is realized by the National Levelling Network (NLN). The normal heights according to Molodensky have been introduced as reference heights in the NLN in 1957. Since then, the gravity correction, which is necessary to determine the reference heights in the NLN, has been obtained by an interpolation either from the simple or complete Bouguer anomalies. We refer to this method as the “original”. Currently, the method based on geopotential numbers is the preferred way to unify the European levelling networks. The core of this article is an analysis of different ways to the gravity determination and their application for the calculation of geopotential numbers at the points of the NLN. The first method is based on the calculation of gravity at levelling points from the interpolated values of the complete Bouguer anomaly using the CBA2G_SK software. The second method is based on the global geopotential model EGM2008 improved by the Residual Terrain Model (RTM) approach. The calculated gravity is used to determine the normal heights according to Molodensky along parts of the levelling lines around the EVRF2007 datum point EH-V. Pitelová (UELN-1905325) and the levelling line of the 2nd order NLN to Kráľova hoľa Mountain (the highest point measured by levelling). The results from our analysis illustrate that the method based on the interpolated value of gravity is a better method for gravity determination when we do not know the measured gravity. It was shown that this method is suitable for the determination of geopotential numbers and reference heights in the Slovak national levelling network at the points in which the gravity is not observed directly. We also demonstrated the necessity of using the precise RTM for the refinement of the results derived solely from the EGM2008.

scholarly journals Global Geopotential Model Evaluations and Local Geoid in Indonesia: A Review

2021 ◽  
Vol 936 (1) ◽  
pp. 012034
Author(s):  
Hamidatul Aminah ◽  
Ira Mutiara Anjasmara
Keyword(s):  
Short Wave ◽  
Global Model ◽  
Geopotential Model ◽  
Geoid Model ◽  
Geospatial Information ◽  
Global Geopotential Model ◽  
Observation Methods ◽  
Gravity Observation ◽  
Main Components ◽  
Local Geoid

Abstract Geoid model was chosen as a vertical reference in Indonesia based on the Head of the Geospatial Information Agency Regulation (Perka BIG) No. 15 of 2013 concerning the Indonesian Geospatial Reference System (SRGI2013). Therefore, the development of local geoid models continues to be carried out to obtain good accuracy. The geoid is formed through three main components: long wave, short wave, and medium wave. One of the longwave components is the global geopotential model obtained from topographic, terrestrial, altimetry, and gravity satellite data. Along with the development of technology and gravity observation methods, the global model has many variations, so it is necessary to determine the global model that is most suitable for the geographical conditions in Indonesia. EGM2008 is often used in local geoid modeling in Indonesia based on research that compares several global models. Still, it does not rule out the possibility of a new global model that is more suitable for Indonesia.

Local geoid model of the Western Desert in Egypt using terrestrial gravity data and global geopotential models

2021 ◽  
Vol 14 (15) ◽  
Author(s):  
Mostafa Ahmed Elwan ◽  
Ahmad Helaly ◽  
Khaled Zharan ◽  
Elsayed Issawy ◽  
Ahmed Abd El-Gawad
Keyword(s):  
Gravity Data ◽  
Western Desert ◽  
Geoid Model ◽  
Terrestrial Gravity ◽  
Geopotential Models ◽  
Local Geoid

scholarly journals Creating and updating of topographic maps height base in the new national spatial coordinate system: case Fergana valley

2021 ◽  
Vol 27 (2) ◽  
pp. 155-164
Author(s):  
Dilbarkhon Fazilova ◽  
Khasan Magdiev
Keyword(s):  
Coordinate System ◽  
High Precision ◽  
Tide Gauge ◽  
Topographic Maps ◽  
Geopotential Model ◽  
Normal System ◽  
Topographic Map ◽  
Coordinate Systems ◽  
Gps Measurements ◽  
Normal Heights

The use of high-precision technology of the global navigation satellite system (GNSS) has put forward the task of developing the methods for the creation and the use of a new national open coordinate system in the Republic of Uzbekistan. In the country, up to now the CS42 coordinate system, based on the Krasovsky ellipsoid used for geodetic works. The Baltic normal system of heights (1977), tied to the mean sea level with the zero mark of the Kronstadt tide gauge, was adopted as a height datum. Due to lack geoid information for the territory of the country determined by modern methods, the realization of a height reference datum becomes an urgent task. The results of GPS measurements usually presented in a coordinate system relative to the WGS-84 ellipsoid, and have to convert to national, local coordinate systems to solve practical problems. The horizontal GPS coordinates can directly use for computational work, but the geodetic heights have to convert to orthometric (or normal) heights for a given area using geoid information. In this work, a study was made of methods for updating the height reference datum of topographic maps at a scale of 1:200,000 using a deformation matrix between two reference coordinate systems for the territory of the Fergana Valley. To convert between geodetic and normal heights between the CS42 and WGS84 coordinate systems, a vertical deformation matrix in the GTX format of the National oceanic and Atmospheric Administration of Canada (NOAA) have created. To create a file of elevation displacements, the results of classical leveling and satellite GPS measurements have used at 144 “common” points of the entire network of the country with known coordinates in two systems. The difference between the “real” values of geodetic heights obtained from GPS measurements and “modeled” ranges from -0.13 m to 0.67 m. It has revealed that the maximum differences in heights are in the area of the Fergana basin itself and may be a consequence of both an anomalous gravitational field in this part of the territory, and an insufficient density of stations of the GPS network in the northeastern part of the area. The normal height values for the updated topographic map in WGS84 have computed using the EGM2008 high precision geopotential model. The discrepancy between the values of heights in CS42 and WGS84 is in the range of -3.93 m and 0.31 m.

A new method of improving global geopotential models regionally using GNSS/levelling data

2020 ◽  
Vol 221 (1) ◽  
pp. 542-549
Author(s):  
Wei Liang ◽  
Roland Pail ◽  
Xinyu Xu ◽  
Jiancheng Li
Keyword(s):  
Least Squares Method ◽  
Satellite System ◽  
New Method ◽  
Height Anomaly ◽  
Geopotential Model ◽  
Disturbing Potential ◽  
Earth Gravity ◽  
Geopotential Models ◽  
Data Points ◽  
Global Navigation Satellite

SUMMARY In this paper, a new method for regionally improving global geopotential models (GGMs) with global navigation satellite system (GNSS)/levelling data is proposed. In this method, the GNNS/levelling data are at first converted to disturbing potential data with inverse Bruns’ formula. Then the systematic errors in disturbing potential data are removed with a three-parameter correction surface. Afterwards, the disturbing potential data on the Earth's surface are downward continued to the surface of an inner sphere with inverse Poisson's integral equation. Global disturbing potential data on the whole sphere could be achieved with combination of the downward continued data and the GGM-derived data. At last, the final regionally improved geopotential model (RIGM) could be recovered from the disturbing potential data using least-squares method. Four RIGM models for Qingdao (QD) are determined based on four different sets of GNSS/levelling data points to validate the capability of the method. The standard deviation of height anomaly errors of RIGM-QDs are nearly 25 and 30 per cent on average smaller than Earth Gravity Model 2008 (EGM2008) on checkpoints and data points, respectively. This means that the RIGM-QDs fit better to the GNSS/levelling network in this area than EGM2008. The results show that the proposed method is successful at improving GGMs in regional area with regional GNSS/levelling data.

scholarly journals Optimum Combinations of GGM and GDEM Models for Precise National Geoid Modelling

2021 ◽  
Author(s):  
Essam Mohamed Al-Karargy ◽  
Gomaa Mohamed Dawod
Keyword(s):  
Least Square ◽  
Global Navigation Satellite Systems ◽  
Geoid Model ◽  
Satellite Systems ◽  
Long Wavelength ◽  
Geopotential Models ◽  
Digital Elevation ◽  
Least Square Collocation ◽  
Global Navigation Satellite ◽  
Local Geoid

This study aims to develop a Local Geoid Model (LGM) for Egypt to determine the optimal combinations of global models with Global Navigation Satellite Systems (GNSS/Levelling) data. A precise national geodetic dataset, four Global Geopotential Models (GGMs), and three global Digital Elevation Models (DEMs) have been utilized. Hence, twelve gravimetric LGMs have been developed using the Least-Square Collocation (LSC) method fitted to GNSS/Levelling data and judged over 100 checkpoints. Results revealed that improvements in local geoid accuracy are attributed mainly to GGMs models representing the long wavelength of the Earth's gravitational field. Regarding DEMs, the accuracy of LGMs does not significantly depend on the utilized DEM. Based on the available data, the attained optimum geoid of Egypt has been developed with a standard deviation, equals 0.129 m.

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