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1

Analysis of differences in accuracy of positioning tied to various CORS networks in Poland: case study

Uznański Andrzej

Reports on Geodesy and Geoinformatics

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2023

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Vol. 116

47--60

EN

Network Real Time Kinematic (NRTK) measurements are currently the most popular surveying method in geodesy. In most countries, there are networks of Continuously Operating Reference Stations (CORS), which form the core of the terrestrial infrastructure that allows for NRTK measurements. In many countries, including Poland, several CORS networks operate in parallel and independently. The paper presents the characteristics of the CORS network in Poland. The results of several day NRTK and Real Time Kinematic (RTK) test measurements performed tied to five CORS networks operating in Poland: ASG-EUPOS, NadowskiNET, SmartNet, TPINETpro, VRSNet.pl, were subjected to a comparative analysis. VRS, FKP, MAC and POJ streams were used in the test measurements. The research mainly concerned the possibility of the occurrence of systematic errors when NRTK and RTK measurements were tied to different CORS networks for the survey of the same points. Conclusions from the comparative analysis of the accuracy and precision of the NRTK and RTK measurement results for each coordinate were also included.

2

Integrated observations on crustal strain‑ionosphere total electron content anomalies before the earthquake

Sharma Gopal, Singh Mutum Somorjit, Aggarwal Shiv Prasad, Romero-Andrade Rosendo

Acta Geophysica

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2023

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Vol. 71, no. 3

1173--1185

EN

Changes in strain (Linear and triangular) rate and Ionosphere Total Electron Content (TEC) before Mw 7.9 2018 Alaska Earthquake are investigated. Ten years of global positioning system (GPS) time series solutions were used for strain estimation in the region before the occurrence of the earthquake using the Haversine formula and triangulation method. Linear strain values suggest an anomaly in strain variation trend near the epicenter. Additionally, daily TEC variations for 30 days before the earthquake occurred were monitored and analysed. Analysis suggests TEC depletion on December 26 2017, and January 16 2018, respectively. TEC values from 60 GPS stations data were interpolated to study the spatial variations of TEC anomaly. Hourly TEC data derived from GPS stations on December 26 2017, and January 16 2018, suggest low TEC zone concentration near to the earthquake epicenter during 1 to 4 UTC. Spatial distribution of TEC values in 2-Dimension corresponding to anomaly time at 60 GPS stations in the vicinity of study area suggests lowest TEC values at stations that lie closer to the epicenter. The study suggests Lithosphere-Ionosphere coupling before Mw 7.9 2018 Alaska Earthquake and recommends developing a TEC-Strain Monitoring System for further validation of the work and for the better study of earthquake precursors based on TEC-Strain anomalies.

3

Prospect of development of the VRSNET reference stations network

Kudas Dawid, Wnęk Agnieszka, Savchyn Ihor

Geomatics, Landmanagement and Landscape

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2020

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no. 2

51--64

PL

VRSNET jest komercyjną aktywną siecią geodezyjną składającą się ze stacji referencyjnych znajdujących się na terytorium Polski oraz na terytorium państw sąsiednich. W pracy przedstawiono analizę przestrzenną lokalizacji stacji permanentnych VRSNET, których anteny i odbiorniki satelitarne w sposób ciągły odbierają i rejestrują sygnały transmitowane przez GNSS (Global Navigation Satellite Systems). Rozważania skupiły się na delimitacji obszaru Polski pod względem potencjalnego zasięgu średniego poszczególnych stacji. W badaniach wykorzystano analizy przestrzenne m.in. diagram Voronoi/Thiessen (tesselacje Dirichleta) oraz bufory przestrzenne. W pracy oceniono geometrię sieci VRSNET dla potrzeb wykonywania pomiarów techniką Real Time Kinematic (RTK) z wykorzystaniem wektorów bazowych opartych wyłącznie na analizowanych stacjach. Podjęto także dyskusję dotyczącą możliwego rozwoju sieci VRSNET poprzez uruchomienie nowych stacji referencyjnych. W wyniku przeprowadzonych analiz przestrzennych wskazano lokalizację i zasięg obszarów wymagających zagęszczenia sieci VRSNET. W obszarach określonych w toku delimitacji powierzchni Polski wskazano lokalizacje 16 nowych stacji referencyjnych. W celu walidacji zagęszczoną o nowoprojektowane stacje sieć VRSNET poddano ponownej ocenie z użyciem diagramu Voronoi/Thiessena oraz buforów przestrzennych. Otrzymane wyniki porównano z parametrami dotyczącymi państwowej sieci ASG-EUPOS (Active Geodetic Network – European Position Determination System). Wykazano wynikającą z zaproponowanego scenariusza rozbudowy sieci VRSNET poprawę parametrów pomiarów techniką RTK. Zagęszczenie sieci może także wpływać pozytywnie na wyniki pomiarów techniką Network Real Time Kinematic (RTN).

EN

The VRSNET is a commercial active geodetic network of reference stations deployed on Polish territory and in neighbouring countries. The paper presents a spatial analysis of locations of VRSNET permanent stations whose antennas and satellite receivers continuously record signals transmitted by Global Navigation Satellite Systems (GNSS). The study focused on delimiting the potential average range of individual stations in Poland. Spatial analyses, including Voronoi/Thiessen diagram (Dirichlet tessellations) and spatial buffers were used in the research. The study evaluated the geometry of the VRSNET network for the Real Time Kinematic (RTK) measurements that use base vectors solely from the analysed stations. Possible development of the VRSNET network through launching new reference stations was elaborated, too. The spatial analyses indicated the localisation and range of areas with an insufficient density of the VRSNET network. The locations of 16 new reference stations have been delimited on Polish territory. The VRSNET network with newly designed stations was reassessed for validation using the Voronoi/Thiessen diagram and spatial buffers. The results were compared with the parameters for the Active Geodetic Network – European Position Determination System (ASG-EUPOS). Improved RTK measurement geometric parameters resulting from the proposed scenario of the VRSNET network development have been demonstrated. Network density can also have a positive impact on the measurement results of the Network Real Time Kinematic (NRTK).

4

An assessment of seasonal variations in the cref cors at the University of Lagos

Nwilo Peter Chigozie, Ayodele Emmanuel Gbenga, Okolie Chukwuma John, Orji Michael Joseph, Marve Mnguhenen Funmilayo, Oyelade Esther Abidemi, Daramola Olagoke Emmanuel

Geomatics, Landmanagement and Landscape

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2020

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no. 1

63--77

EN

Continuously Operating Reference Stations (CORS) are reference stations of the Global Navigation Satellite System (GNSS), providing fundamental positioning infrastructure that is accurate and reliable. As such, CORS are designed to meet the needs of a wide range of users requiring high three-dimensional (3D) positional accuracy. The Continuously Operating Reference Station at the Engineering Faculty (CREF), University of Lagos was set up in order to support research applications in Surveying, Mapping and Geodesy. This study evaluates the seasonal variations in the 3D coordinates of CREF using metrics such as coordinate differences, Standard Deviation (SD) and Standard Error (SE). The Canadian Spatial Reference System (CSRS), known as CSRS – Precise Point Positioning (CSRS-PPP) was used to compute the station’s daily coordinates over a three-year period from 2016 to 2018. In the analysis, the daily coordinates were divided into two seasons - the wet and the dry. The results obtained show that the dry and the wet seasons had SDs (5.4 mm, 3.9 mm, and 2.0 mm) and (5.2 mm, 18.6 mm and 14.4 mm) in the x, y and z-directions respectively. Generally, the dry season presents a better result than the wet season as revealed by the accuracy metrics. These results have led to an increased understanding of the seasonal variability inherent in the data acquired by GNSS CORS, and must be taken into consideration: in particular, for GNSS applications such as the weather prediction and water vapour estimation. This study concludes that more needs to be done regarding the maintenance of CREF to ensure data continuity and reliability for geodetic studies.

5

Future of National Reference Frames – from static to kinematic?

Poutanen M., Häkli P.

Geodesy and Cartography

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2018

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Vol. 67, no. 1

117--129

EN

Technical development, new applications and requests for increased accuracy in georeferencing are setting new demands for accuracy and reliability of reference frames. Due to crustal deformations and local movements of benchmarks, a static reference network deteriorates with time, thus eventually requiring update of the whole system. Technically, renewal of a reference frame is straightforward and should be done whenever enough new data or updated information exist to get an improvement in accuracy. An example is the International Terrestrial Reference Frame, ITRF, which is renewed regularly. The situation is more complicated with national reference frames which may have been given a legal status, and parameters defined by the national legislation. Even without that, renewal and implementation of such a frame is a multi-million euro project taking years to complete. Crustal deformations and movements deteriorate static reference frames (defined by fixed/static coordinates of benchmarks) with time. Eventually, distortions in a static reference frame will become bigger than the uncertainties of GNSS measurements, thus deteriorating the obtainable accuracy of the measurement technique. Instead of a static reference frame, one can use semi-kinematic or kinematic approach where either the transformation from global to the national reference frame or the coordinates of reference frame benchmarks are time-dependent. In this paper we give a short overview of the topic, and discuss on technical issues and future aspects of the reference frames in the viewpoint of National Mapping and Cadastre Authorities (NMA) with an example on the national strategy in Finland.

6

Design and implementation of large vessel navigation system based on beidou cors

Huang P., Liu Y., Du Z., Chen Q., Chen J.

Polish Maritime Research

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2017

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S 3

12--15

EN

The ship’s pilot can obtain the ship auxiliary information through the navigation system, when berthing system can display the parameters such as traverse speed and distance of the ship. But most of the system data show that there are insufficient precision. Taking the CORS system to obtain the location information, data Calculation of Berthing System based on Polar Coordinate Algorithm, this paper puts forward a solution to the “dead point” of the berthing and aiding system, which has a certain reference value for the design of the ship berthing assistance system.

7

Urban area GPS positioning accuracy using ASG-EUPOS POZGEO service as a function of session duration

Dawidowicz K., Krzan G., Świątek K.

Artificial Satellites : Journal of Planetary Geodesy

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2014

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Vol. 49, No. 1

33--42

EN

GNSS observations carried out in a network of Continuously Operating Reference Station (CORS) are a complex systems which offer post-processing as well as corrections sent in realtime. In Poland, such a system has been in operation since June 2008, known as the Polish Active Geodetic Network (ASG-EUPOS). Usually the measurements performed in real time characterized lower accuracy than static measurements. For users who demand the highest precision results the post-processing services are provided. The paper presents an analysis of the position determination accuracy using ASG-EUPOS POZGEO service. It is well known that the final accuracy is e.g. the measuring conditions, time of observations or number of measured frequencies dependent. We processed 4 consecutive days of GPS data to determine how the accuracy of derived positional coordinates depends on the length of the observing session, the characteristics of horizon visibility on points and the used in post-processing observations (L1 or L1+L2). The POZGEO results show that horizontal accuracies of about 1-2 cm and vertical accuracies of 4 cm are achievable provided 0.5 hours dual frequency GPS data. The accuracy clearly decreases for point measured under conditions of strongly limited satellite availability.

8

Analiza porównawcza wybranych aktywnych sieci geodezyjnych

Specht C., Skóra M.

Zeszyty Naukowe Akademii Marynarki Wojennej

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2009

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R. 50 nr 3 (178)

39-54

PL

W artykule przedstawiono uruchomioną w czerwcu 2008 roku polską aktywną sieć geodezyjną ASG-EUPOS na tle wybranych aktywnych sieci geodezyjnych działających na świecie. W zasadniczej części publikacji wyróżniono przestrzeń porównawczą obejmującą architekturę i usługi (serwisy) wraz z metodami radiowej transmisji danych telemetrycznych zgodnych ze standardem RTCM SC-104. Artykuł kończą uogólnione wnioski przedstawiające zalety poszczególnych rozwiązań, które mogą być pomocne przy modernizacji systemów obecnie eksploatowanych oraz projektowaniu i budowie analogicznych.

EN

The article presents comparable analyses between the Polish Active Geodetic Network ASG-EUPOS established in June 2008 and other selected networks like: CORS (US), SAPOS (Germany), SWEPOS (Sweden), OS - AGN (UK). Architecture, services and methods of GPS pseudorange correction transmission according to RTCM SC-104 standard were used for comparisons. Advantages and disadvantages of different national active geodetic network solutions are presented as conclusions.