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Reliability of CSRS-PPP for validating the Egyptian geodetic CORS networks

Abdallah Ashraf, Agag Tarek

Artificial Satellites : Journal of Planetary Geodesy

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2022

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Vol. 57, No. 1

58--76

EN

The development, utilization, and maintenance of continuously operating reference stations (CORS) network are vital in many areas of surveying and geodesy, such as controlling geodetic networks, developing local ionospheric models, and estimating the tectonic plate movements. Accordingly, the Egyptian Surveying Authority (ESA) established a CORS network consisting of 40 stations covering the Nile valley and its delta in 2011. CORS collect global navigation satellite system (GNSS) data. Recently, Egypt has witnessed rapid growth in many infrastructure projects and the development of new cities on a national scale. Therefore, there is an urgent need to investigate the ESA-CORS accuracy; the quality of data from the ESA-CORS must be considered for monitoring continuous tectonic motion, coordinating changes, and for Egypt’s development plan. Contemporary research worldwide identified considerable benefits of the precise point positioning (PPP) solution of dual- or singlefrequency GNSS data. This study investigates the reliability of using the CSRS-PPP service for three consecutive observation days of 32 ESA-CORS networks in Egypt and the surrounding six international GNSS services (IGS)-CORS. For ESA-CORS, the PPP solution showed a root mean square error (RMSE) value of 6 mm (standard deviation [SD] = 3–4 mm) in east and north; for the height direction, the solution indicated an RMSE value of 22 mm (SD was about 14 mm). At a confidence level of 95%, this study revealed that SD95% was 2 mm in east and north directions and 6-7 mm for the height direction. This study shows that the PPP solution shown from the ESA-CORS stations is associated with two times better for horizontal and four times for the height direction than the delivered form ESA-CORS stations.

2

Performance assessment of PPP-AR positioning and zenith total delay estimation with modernized CSRS-PPP

Atiz Omer Faruk, Kalayci Ibrahim

Artificial Satellites : Journal of Planetary Geodesy

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2021

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Vol. 56, No. 2

18--34

EN

The precise point positioning (PPP) method has become more popular due to powerful online global navigation satellite system (GNSS) data processing services, such as the Canadian Spatial Reference System-PPP (CSRS-PPP). At the end of 2020, the CSRS-PPP service launched the ambiguity resolution (AR) feature for global positioning system (GPS) satellites. More reliable results are obtained with AR compared to the results with traditional ambiguity-float PPP. In this study, the performance of the modernized CSRS-PPP was comparatively assessed in terms of static positioning and zenith total delay (ZTD) estimation. Data for 1 month in the year 2019 obtained from 47 international GNSS service (IGS) stations were processed before and after modernization of the CSRS-PPP. The processes were conducted for GPS and GPS + GLONASS (GLObalnaya NAvigatsionnaya Sputnikovaya Sistema) satellite combinations. Besides, the results were analyzed in terms of accuracy and convergence time. According to the solutions, the AR feature of the CSRS-PPP improved the accuracy by about 50% in the east component for GPS + GLONASS configuration. The rootmean-square error (RMSE) of the ZTD difference between modernized CSRS-PPP service and IGS final troposphere product is 5.8 mm for the GPS-only case.

3

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.

4

Efficiency of using GNSS-PPP for digital elevation model (DEM) production

Abdallah Ashraf, Saifeldin Amgad, Abomariam Abdelhamid, Ali Reda

Artificial Satellites : Journal of Planetary Geodesy

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2020

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Vol. 55, No. 1

17--28

EN

In the developing countries, cost-effective observation techniques are very important for earthwork estimation, map production, geographic information systems, and hydrographic surveying. One of the most cost-effective techniques is Precise Point Positioning (PPP); it is a Global Navigation Satellite Systems (GNSS) positioning technique to compute precise positions using only a single GNSS receiver. This study aims to evaluate the efficiency of using Global Positioning System (GPS) and GPS/ Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) post-processed kinematic PPP solution for digital elevation model (DEM) production, which is used in earthwork estimation. For this purpose, a kinematic trajectory has been observed in New Aswan City in an open sky area using dual-frequency GNSS receivers. The results showed that, in case of using GPS/GLONASS PPP solution to estimate volumes, the error in earthwork volume estimation varies between 0.07% and 0.16% according to gridding level. On the other hand, the error in volume estimation from GPS PPP solution varies between 0.40% and 0.99%.

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Dokładność wyznaczania pozycji z zastosowaniem permanentnych usług internetowych PPP (Precise Point Positioning)

Malinowski M.

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

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2017

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z. 64, nr 4/I

297--313

PL

Precyzyjne pozycjonowanie PPP to metoda wyznaczania pozycji przy pomocy samodzielnego odbiornika GNSS. Może stanowić alternatywną technikę do pomiarów różnicowych gdzie niezbędnym jest utrzymanie łączności z pojedynczą stacją RTK lub regionalną siecią stacji referencyjnych RTN. Metoda precyzyjnego pomiaru PPP może w szczególności sprawdzić się w obszarach o słabo rozwiniętej infrastrukturze stacji naziemnych. W niniejszej pracy przedstawiono wyniki analizy dokładności precyzyjnego wyznaczania pozycji na wierzchołkach trójkątnej osnowy dla obserwacji trwających od 0,5 do 6 godzin z wykorzystaniem bezpłatnych permanentnych usług internetowych realizujących obliczenia techniką PPP jak: APPS, CSRS–PPP, magicGNSS. Dla każdego punktu osnowy pomiarowej wykonano obliczenia wykorzystując obserwacje GPS i uwzględniając produkty Final. Wykonano ocenę wpływu dokładności jednoczesnego pozycjonowania trzech punktów osnowy pomiarowej na zmianę odległości zredukowanej i wysokości względnej między wierzchołkami badanego trójkąta osnowy.

EN

Precise Point Positioning (PPP) is a technique used to determine high accuracy position with a single GNSS receiver. May be an alternative solution to differential measurements, where maintaining a connection with a single Real Time Kinematic (RTK) station or a regional Real Time Network (RTN) of reference stations is necessary. This situation is especially common in areas with poorly developed infrastructure of ground stations. This paper presents the results of a comparative analysis of accuracy of absolute determination of position from observations which last between 0,5 to 6 hours with the use of four permanent free online web services which execute calculations with PPP technique such as: Automatic Precise Positioning Service (APPS), Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP), GNSS Analysis and Positioning Software (GAPS) and magicPPP - Precise Point Positioning Solution (magicGNSS). For each point of test network, calculations were made using solely GPS observations and taking into account Final products. An evaluation of the impact on the accuracy of simultaneous positioning of three points test network on the change of the horizontal distance and the relative height difference between measured triangle vertices was also conducted.

6

A comparative study of Precise Point Positioning (PPP) accuracy using online services

Malinowski M., Kwiecień J.

Reports on Geodesy and Geoinformatics

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2016

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Vol. 102

15--31

EN

Precise Point Positioning (PPP) is a technique used to determine the position of receiver antenna without communication with the reference station. It may be an alternative solution to differential measurements, where maintaining a connection with a single RTK station or a regional network of reference stations RTN is necessary. This situation is especially common in areas with poorly developed infrastructure of ground stations. A lot of research conducted so far on the use of the PPP technique has been concerned about the development of entire day observation sessions. However, this paper presents the results of a comparative analysis of accuracy of absolute determination of position from observations which last between 1 to 7 hours with the use of four permanent services which execute calculations with PPP technique such as: Automatic Precise Positioning Service (APPS), Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP), GNSS Analysis and Positioning Software (GAPS) and magicPPP - Precise Point Positioning Solution (magicGNSS). On the basis of acquired results of measurements, it can be concluded that at least two-hour long measurements allow acquiring an absolute position with an accuracy of 2-4 cm. An evaluation of the impact on the accuracy of simultaneous positioning of three points test network on the change of the horizontal distance and the relative height difference between measured triangle vertices was also conducted. Distances and relative height differences between points of the triangular test network measured with a laser station Leica TDRA6000 were adopted as references. The analyses of results show that at least two hours long measurement sessions can be used to determine the horizontal distance or the difference in height with an accuracy of 1-2 cm. Rapid products employed in calculations conducted with PPP technique reached the accuracy of determining coordinates on a close level as in elaborations which employ Final products.