Wyniki wyszukiwania - Biblioteka Nauki

1

Overview and performance of the Ukrainian SLR station “Lviv-1831”

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Blagodyr J. , Bilinsky A. , Martynyuk-Lototsky K. , Lohvynenko O. , Virun N.

Artificial Satellites : Journal of Planetary Geodesy

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2007

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tom Vol. 42, No. 1

9--15

EN

The paper presents the current status and performance of the SLR station “Lviv-1831”. The present equipment allows ranging of satellite not lower than 900 km with a single shot precision about 50 mm. The team works over system upgrade and performance improvement. It includes: neutral filters wheel developing for equilibration of the amplitude of reflected pulses from different satellites, building up the shutter in the face of PMT for the spurious light pulses blocking. Also the new adjusting of the telescope optical mechanical systems was made. After that investigation the new telescope error model was built with an accuracy 20arcsec that allowed at the first time test ranging of the “shadowed” satellite passes. In the near future the team will finish installation and testing of the new PMT Hamamatsu H6780. Maiden upgrades should better the performance and ranging accuracy by the factor of 2-3.

2

Tectonic plates parameters estimated in International Terrestrial Reference Frame ITRF2008 based on DORIS stations

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Kraszewska K. , Jagoda M. , Rutkowska M.

Acta Geophysica

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2018

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tom Vol. 66, no. 4

509--521

EN

This paper concerns an analysis of the accuracy of the estimated parameters X (U, K, x) which define the tectonic plate motions. The study is based on the velocities of station positions in the IERS (International Earth Rotation and Reference Systems Service) which has published new realization of the International Terrestrial Reference System—ITRF2008 for Doppler Orbitography by Radiopositioning Integrated on Satellite DORIS technique. Eurasian, African, Australian, North American, Australian, Pacific, Antarctic and South American plates were used in the analysis. The influence of the number and localization of stations on the plate surface on the estimation accuracy of the tectonic plate motion parameters were discussed. The results were compared with the APKIM 2005 IGN model and our earlier estimation for the SLR technique. In general, a remarkable concurrent agreement between the present and the APKIM 2005 solutions was found.

3

Application of the undifferenced GNSS precise positioning in determining coordinates in national reference frames

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Krzan G. , Stępniak K.

Artificial Satellites : Journal of Planetary Geodesy

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2017

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tom Vol. 52, No. 3

49--69

EN

In high-accuracy positioning using GNSS, the most common solution is still relative positioning using double-difference observations of dual-frequency measurements. An increasingly popular alternative to relative positioning are undifferenced approaches, which are designed to make full use of modern satellite systems and signals. Positions referenced to global International Terrestrial Reference Frame (ITRF2008) obtained from Precise Point Positioning (PPP) or Undifferenced (UD) network solutions have to be transformed to national (regional) reference frame, which introduces additional bases related to the transformation process. In this paper, satellite observations from two test networks using different observation time series were processed. The first test concerns the positioning accuracy from processing one year of dual-frequency GPS observations from 14 EUREF Permanent Network (EPN) stations using NAPEOS 3.3.1 software. The results were transformed into a national reference frame (PL-ETRF2000) and compared to positions from an EPN cumulative solution, which was adopted as the true coordinates. Daily observations were processed using PPP and UD multi-station solutions to determine the final accuracy resulting from satellite positioning, the transformation to national coordinate systems and Eurasian intraplate plate velocities. The second numerical test involved similar processing strategies of post-processing carried out using different observation time series (30 min., 1 hour, 2 hours, daily) and different classes of GNSS receivers. The centimeter accuracy of results presented in the national coordinate system satisfies the requirements of many surveying and engineering applications.

4

Testing the number of IGS stations required for accurate alignment of the Thai GPS network and ITRF2005 using the GIPSY software

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Satirapod C. , Payakleard P. , Simons W. J. F. , Kriengkraiwasin S.

Artificial Satellites : Journal of Planetary Geodesy

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2013

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tom Vol. 48, No. 1

1--13

EN

Since its introduction in 1990s, the GPS Precise Point Positioning (PPP) technique has been widely used for many high precision positioning applications such as the study of tectonic plate motion, establishment of national and regional reference frames and so on. Among the GPS PPP software packages, the GIPSY-OASIS II software package is the one of the most popular software package used by many research institutes worldwide. The processing of GPS data with the GIPSY-OASIS II software requires three main steps. The first step is to compute a daily GPS solution for each station and the second step is to combine daily GPS solutions into a multi-day averaged solution. The final step is to transform these multi-day averaged solutions into the International Terrestrial Reference Frame (ITRF) coordinate solution and this step generally requires the use of available International GNSS service (IGS) stations to compute the required transformation parameters. In order to obtain high precision ITRF coordinate solutions, an investigation on a selection of IGS stations used for aligning the multi-day averaged solution into ITRF is therefore needed. This study aims to investigate the effect of number of IGS stations used for aligning the multi-day averaged solutions into the final ITRF coordinate solution in Thai region. Data from two different GPS campaigns (with epochs before and after the 2004 SumatraAndaman earthquake) measured by the Royal Thai Survey Department (RTSD) were used in this investigation. By varying the number of IGS station used in the alignment step, results indicate that the use of at least 16 IGS stations in the alignment process can produce reliable and accurate ITRF solutions especially those impacted by the large earthquake.

5

Quality assessment of satellite laser ranging stations operating in 2020

51%

Schillak S. , Lejba P. , Michałek P. , Smagło A.

Aviation and Security Issues

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2023

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tom No. 2

157--179

EN

The paper assesses the quality of satellite laser ranging stations that were operational in 2020. The assessment is based on the results obtained from the LAGEOS-1 and LAGEOS-2 satellites between 2011 and 2020. In 2020, 41 SLR stations conducted laser observations on both LAGEOS satellites. Out of these stations, 20 had been making observations for ten years, while some stations started their observations during this period, resulting in a shorter observation period. NASA's GEODYN-II orbital software was used to compute the satellite orbits for fifteen core stations. The accuracy of the observations from each station was evaluated by determining the stability of the designated coordinates (3DRMS) in the International Terrestrial Reference Frame 2020. The results show that 16 stations achieved accuracy ranging from 4 mm to 10 mm, 17 stations between 10 mm and 15 mm, and 8 stations above 15 mm. Similarly, the standard deviation of the determined coordinates ranged from 1.0 mm to 2.6 mm, from 3.0 mm to 4.0 mm, and above 4.0 mm, respectively. The discussion focuses on the reasons for the inadequate accuracy in determining the coordinates for most stations. These reasons include a lack of sufficient normal points for most stations, a significant random scatter of normal points in the orbit, and insufficient long-term stability of systematic deviations. It is important to note that the results for both LAGEOS satellites are highly consistent.

PL

W pracy przedstawiono ocenę jakości stacji laserowych działających w roku 2020 na podstawie wyników uzyskanych dla satelitów LAGEOS-1 i LAGEOS-2 w latach 2011-2020. W 2020 roku obserwacje laserowe obu satelitów LAGEOS prowadziło 41 stacji SLR, z czego 20 stacji zrealizowały obserwacje w ciągu dziesięciu lat, pozostałe stacje rozpoczynały obserwacje w tym okresie, stąd krótszy okres obserwacji. Orbity satelitów zostały obliczone za pomocą programu orbitalnego GSFC NASA GEODYN-II dla wybranych piętnastu najlepszych stacji. Dokładność obserwacji poszczególnych stacji oceniono na podstawie stabilności wyznaczonych współrzędnych (3DRMS) w układzie International Terrestrial Reference Frame 2020. Wyniki pokazują, że 16 stacji uzyskało dokładność w zakresie od 4 mm do 10 mm, 17 stacji od 10 mm do 15 mm i 8 stacji powyżej 15 mm. Podobny rozkład przedstawia odchylenie standardowe wyznaczonych współrzędnych, odpowiednio od 1,0 mm do 2,6 mm, od 3,0 mm do 4,0 mm i powyżej 4,0 mm. Omówiono przyczyny niewystarczającej jakości wyznaczania współrzędnych dla większości stacji, do których należy zaliczyć zbyt małą ilość punktów normalnych, duży rozrzut przypadkowy punktów normalnych na orbicie, niewystarczającą stabilność odchyleń systematycznych. Należy podkreślić, że wyniki dla obu satelitów LAGEOS są bardzo zgodne.