Abstract In this paper, we make an attempt to use the QHY174M-GPS camera for the photometry research of fast-rotating artificial objects including debris, satellites and rocket bodies. This device is useful for imaging occultations, eclipses, meteors, and so on due to a highly precise recording of the time (GPS-based) and location of the observation on every frame and fast readout of the CMOS detector. The precision of time registration by the QHY174M-GPS camera is at the level of microseconds. All light curves obtained by studied camera during observations of artificial satellites in this work were carried out at Derenivka Observatory of Uzhhorod National University, Ukraine. The created photometric system with QHY174M-GPS camera as the detector and reflector telescope with parameters D=120mm, F=114mm, FOV=2.82°1.76° was calibrated. For target observations, SharpCap software was used. For the purposes of photometry processing, ccd_phot software was developed using Python 3.8 programming language with astropy and photutils packages. Photometry observations of artificial satellites of the Earth and standard stars were carried out. Over 80 lightcurves of artificial satellites were obtained. Comparing synchronous observations from two sites, separated 15 km from each other, we can conclude that photometry on the QHY174M-GPS camera gave us the same shape of lightcurve and additional advantages, such as time of exposure or simplicity of usage.
{"title":"QHY-174M-GPS Camera as the Device for Photometry of Artificial Satellites","authors":"V. Kudak, V. Perig","doi":"10.2478/arsa-2022-0003","DOIUrl":"https://doi.org/10.2478/arsa-2022-0003","url":null,"abstract":"Abstract In this paper, we make an attempt to use the QHY174M-GPS camera for the photometry research of fast-rotating artificial objects including debris, satellites and rocket bodies. This device is useful for imaging occultations, eclipses, meteors, and so on due to a highly precise recording of the time (GPS-based) and location of the observation on every frame and fast readout of the CMOS detector. The precision of time registration by the QHY174M-GPS camera is at the level of microseconds. All light curves obtained by studied camera during observations of artificial satellites in this work were carried out at Derenivka Observatory of Uzhhorod National University, Ukraine. The created photometric system with QHY174M-GPS camera as the detector and reflector telescope with parameters D=120mm, F=114mm, FOV=2.82°1.76° was calibrated. For target observations, SharpCap software was used. For the purposes of photometry processing, ccd_phot software was developed using Python 3.8 programming language with astropy and photutils packages. Photometry observations of artificial satellites of the Earth and standard stars were carried out. Over 80 lightcurves of artificial satellites were obtained. Comparing synchronous observations from two sites, separated 15 km from each other, we can conclude that photometry on the QHY174M-GPS camera gave us the same shape of lightcurve and additional advantages, such as time of exposure or simplicity of usage.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"57 1","pages":"47 - 57"},"PeriodicalIF":0.9,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42858198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Nowadays, theglobal navigation satellite system (GNSS) positioning techniques based on the International GNSS Service (IGS) products are extensively used for various precise applications. However, specific conditions such as the dual-frequency observations and the final IGS products are required. Consequently, the absence of the final IGS data and using single-frequency observations will degrade these techniques’ accuracy. In this paper, two algorithms through two separated stages are formulated for improving the single-frequency GNSS observations by using one GNSS receiver based on the broadcast ephemerides in real time or close to real time. The first algorithm represents the preparation stage for the second one. It classifies the observations by separating the optimal values of position dilution of precision (PDOP) and the number of satellites (NOS), as well as the corresponding values of coordinates. The second stage includes an algorithm based on the artificial neural network (ANN) approach, which is set at the ANN variables that produce the best precision through the applied tests at the present study. Binary numbers, log sigmoid-Purelin, cascade forward net, and one hidden layer with a size of 10 neurons are the optimal variables of ANN inputs format, transfer functions constellations, feedforward net type, and the number of hidden layers (NHL) and its size, respectively. The simulation results show that the designed algorithms produce a significant improvement in the horizontal and vertical components. Lastly, an evaluation stage is performed in the case of dual-frequency observations by using broadcast ephemerides. The simulation outputs indicate that the precision at applying the proposed integration is completely enhanced compared with the outputs of IGS final data.
{"title":"Integration of Artificial Neural Network and the Optimal GNSS Satellites’ Configuration for Improving GNSS Positioning Techniques (A Case Study in Egypt)","authors":"Mustafa K. Alemam, B. Yong, Abubakar S. Mohammed","doi":"10.2478/arsa-2022-0002","DOIUrl":"https://doi.org/10.2478/arsa-2022-0002","url":null,"abstract":"Abstract Nowadays, theglobal navigation satellite system (GNSS) positioning techniques based on the International GNSS Service (IGS) products are extensively used for various precise applications. However, specific conditions such as the dual-frequency observations and the final IGS products are required. Consequently, the absence of the final IGS data and using single-frequency observations will degrade these techniques’ accuracy. In this paper, two algorithms through two separated stages are formulated for improving the single-frequency GNSS observations by using one GNSS receiver based on the broadcast ephemerides in real time or close to real time. The first algorithm represents the preparation stage for the second one. It classifies the observations by separating the optimal values of position dilution of precision (PDOP) and the number of satellites (NOS), as well as the corresponding values of coordinates. The second stage includes an algorithm based on the artificial neural network (ANN) approach, which is set at the ANN variables that produce the best precision through the applied tests at the present study. Binary numbers, log sigmoid-Purelin, cascade forward net, and one hidden layer with a size of 10 neurons are the optimal variables of ANN inputs format, transfer functions constellations, feedforward net type, and the number of hidden layers (NHL) and its size, respectively. The simulation results show that the designed algorithms produce a significant improvement in the horizontal and vertical components. Lastly, an evaluation stage is performed in the case of dual-frequency observations by using broadcast ephemerides. The simulation outputs indicate that the precision at applying the proposed integration is completely enhanced compared with the outputs of IGS final data.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"57 1","pages":"18 - 46"},"PeriodicalIF":0.9,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45605737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The development, utilization, and maintenance of continuously operating reference stations (CORS) network are vital in many areas of surveying and geodesy, such as controllinggeodetic networks, developinglocal 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 single-frequency 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.
{"title":"Reliability of CSRS-PPP for Validating the Egyptian Geodetic Cors Networks","authors":"A. Abdallah, T. Agag","doi":"10.2478/arsa-2022-0004","DOIUrl":"https://doi.org/10.2478/arsa-2022-0004","url":null,"abstract":"Abstract The development, utilization, and maintenance of continuously operating reference stations (CORS) network are vital in many areas of surveying and geodesy, such as controllinggeodetic networks, developinglocal 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 single-frequency 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.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"57 1","pages":"58 - 76"},"PeriodicalIF":0.9,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43456198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The release of low-cost dual-frequency (DF) global navigation satellite system (GNSS) modules provides an opportunity for low-cost precise positioning to support autonomous vehicle applications. The new GNSS modules support the US global positioning system (GPS) L1C/L2C or L5 civilian signals, the Russian GNSS Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS) L1/L2, Europe’s GNSS Galileo E1/E5b, and Chinese GNSS BeiDou B1/B2 signals. The availability of the DF measurements allows for removal of the ionospheric delay, enhancing the obtained positioning accuracy. Unfortunately, however, the L2C signals are only transmitted by modernized GPS satellites. This means that fewer GPS DF measurements are available. This, in turn, might affect the accuracy and the convergence of the GPS-only precise point positioning (PPP) solution. Multi-constellation GNSS PPP has the potential to improve the positioning accuracy and solution convergence due to the high redundancy of GNSS measurements. This paper aims to assess the performance of real-time quad-constellation GNSS PPP using the low-cost u-blox Z9D-F9P module. The assessment is carried out for both open-sky and challenging environment scenarios. Static, simulated-kinematic, and actual field-kinematic trials have been carried out to evaluate real-time PPP performance. Pre-saved real-time precise orbit and clock products from the Centre National d’Etudes Spatiales are used to simulate the real-time scenario. It is shown that the quad-constellation GNSS PPP using the low-cost u-blox Z9D-F9P module achieves decimeter-level positioning accuracy in both the static and simulated-kinematic modes. In addition, the PPP solution convergence is improved compared to the dual- and triple-constellation GNSS PPP counterparts. For the actual kinematic trial, decimeter-level horizontal positioning accuracy is achieved through the GPS + GLONASS + Galileo PPP compared with submeter-level positioning accuracy for the GPS + GLONASS and GPS + Galileo PPP counterparts. Additionally, submeter-level vertical positioning accuracy is achieved through the GPS + GLONASS + Galileo PPP compared with meter-level positioning accuracy for GPS + GLONASS and GPS + Galileo PPP counterparts.
{"title":"Performance Assessment of Real-Time Multiconstellation GNSS PPP Using a Low-Cost Dual-Frequency GNSS Module","authors":"A. Elmezayen, A. El-Rabbany","doi":"10.2478/arsa-2021-0005","DOIUrl":"https://doi.org/10.2478/arsa-2021-0005","url":null,"abstract":"Abstract The release of low-cost dual-frequency (DF) global navigation satellite system (GNSS) modules provides an opportunity for low-cost precise positioning to support autonomous vehicle applications. The new GNSS modules support the US global positioning system (GPS) L1C/L2C or L5 civilian signals, the Russian GNSS Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS) L1/L2, Europe’s GNSS Galileo E1/E5b, and Chinese GNSS BeiDou B1/B2 signals. The availability of the DF measurements allows for removal of the ionospheric delay, enhancing the obtained positioning accuracy. Unfortunately, however, the L2C signals are only transmitted by modernized GPS satellites. This means that fewer GPS DF measurements are available. This, in turn, might affect the accuracy and the convergence of the GPS-only precise point positioning (PPP) solution. Multi-constellation GNSS PPP has the potential to improve the positioning accuracy and solution convergence due to the high redundancy of GNSS measurements. This paper aims to assess the performance of real-time quad-constellation GNSS PPP using the low-cost u-blox Z9D-F9P module. The assessment is carried out for both open-sky and challenging environment scenarios. Static, simulated-kinematic, and actual field-kinematic trials have been carried out to evaluate real-time PPP performance. Pre-saved real-time precise orbit and clock products from the Centre National d’Etudes Spatiales are used to simulate the real-time scenario. It is shown that the quad-constellation GNSS PPP using the low-cost u-blox Z9D-F9P module achieves decimeter-level positioning accuracy in both the static and simulated-kinematic modes. In addition, the PPP solution convergence is improved compared to the dual- and triple-constellation GNSS PPP counterparts. For the actual kinematic trial, decimeter-level horizontal positioning accuracy is achieved through the GPS + GLONASS + Galileo PPP compared with submeter-level positioning accuracy for the GPS + GLONASS and GPS + Galileo PPP counterparts. Additionally, submeter-level vertical positioning accuracy is achieved through the GPS + GLONASS + Galileo PPP compared with meter-level positioning accuracy for GPS + GLONASS and GPS + Galileo PPP counterparts.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"56 1","pages":"37 - 56"},"PeriodicalIF":0.9,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47726594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Łyszkowicz, R. Pelc-Mieczkowska, A. Bernatowicz, S. Savchuk
Abstract The aim of this work is to explore, for the first time in Poland, the possibility of determining Earth’s crust movements from permanent observations at selected permanent stations using the GipsyX software for a period of 8 years (2011–2018) in the ITRF2014 reference frame. The data used in this work are from 15 Aktywna Sieć Geodezyjna (ASG)-EUPOS stations from 2011 to 2018, which are also European Permanent Network (EPN) stations. The stations Borowa Góra, Borowiec, Józefosław, Lamkówko, and Wroclaw are also International Global Navigation Satellite Systems (GNSS) Service (IGS) stations. Daily data, rinex files, for these stations have been made available for this work by the Main Office of Surveying and Cartography. The calculations were made using the GipsyX software in the ITRF14 reference frame. The tests performed have shown that daily solutions from 8-year-long time series give secular trends with an accuracy of 0.01 mm/yr. Our results suggest that there are small differences in horizontal and vertical velocities and in the accuracy estimated between our and EPN solutions. At some stations, for example, Łódź, the differences are much larger. The impact of additional GNSS observations on the accuracy of determination of horizontal and vertical movements of the Earth’s crust shows a submillimeter accuracy in computed coordinates of stations even at a relatively small time interval. It means that multi-GNSS Precise Point Positioning (PPP) processing can be used in the future for the estimation of geodynamic processes.
{"title":"First Results of Time Series Analysis of the Permanent GNSS Observations at Polish EPN Stations Using GipsyX Software","authors":"A. Łyszkowicz, R. Pelc-Mieczkowska, A. Bernatowicz, S. Savchuk","doi":"10.2478/arsa-2021-0008","DOIUrl":"https://doi.org/10.2478/arsa-2021-0008","url":null,"abstract":"Abstract The aim of this work is to explore, for the first time in Poland, the possibility of determining Earth’s crust movements from permanent observations at selected permanent stations using the GipsyX software for a period of 8 years (2011–2018) in the ITRF2014 reference frame. The data used in this work are from 15 Aktywna Sieć Geodezyjna (ASG)-EUPOS stations from 2011 to 2018, which are also European Permanent Network (EPN) stations. The stations Borowa Góra, Borowiec, Józefosław, Lamkówko, and Wroclaw are also International Global Navigation Satellite Systems (GNSS) Service (IGS) stations. Daily data, rinex files, for these stations have been made available for this work by the Main Office of Surveying and Cartography. The calculations were made using the GipsyX software in the ITRF14 reference frame. The tests performed have shown that daily solutions from 8-year-long time series give secular trends with an accuracy of 0.01 mm/yr. Our results suggest that there are small differences in horizontal and vertical velocities and in the accuracy estimated between our and EPN solutions. At some stations, for example, Łódź, the differences are much larger. The impact of additional GNSS observations on the accuracy of determination of horizontal and vertical movements of the Earth’s crust shows a submillimeter accuracy in computed coordinates of stations even at a relatively small time interval. It means that multi-GNSS Precise Point Positioning (PPP) processing can be used in the future for the estimation of geodynamic processes.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"56 1","pages":"101 - 118"},"PeriodicalIF":0.9,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46511181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract To estimate Moho depth, geoid, gravity anomaly, and other geopotential functionals, gravity data is needed. But, gravity survey was not collected in equal distribution in Ethiopia, as the data forming part of the survey were mainly collected on accessible roads. To determine accurate Moho depth using Global Gravity Models (GGMs) for the study area, evaluation of GGMs is needed based on the available terrestrial gravity data. Moho depth lies between 28 km and 32 km in Afar. Gravity disturbances (GDs) were calculated for the terrestrial gravity data and the recent GGMs for the study area. The model-based GDs were compared with the corresponding GD obtained from the terrestrial gravity data and their differences in terms of statistical comparison parameters for determining the best fit GGM at a local scale in Afar. The largest standard deviation (SD) (36.10 mGal) and root mean square error (RMSE) (39.00 mGal) for residual GD and the lowest correlation with the terrestrial gravity (0.61 mGal) were obtained by the satellite-only model (GO_CONS_GCF_2_DIR_R6). The next largest SD (21.27 mGal) and RMSE (25.65 mGal) for residual GD were obtained by the combined gravity model (XGM2019e_2159), which indicates that it is not the best fit model for the study area as compared with the other two GGMs. In general, the result showed that the combined models are more useful tools for modeling the gravity field in Afar than the satellite-only GGMs. But, the study clearly revealed that for the study area, the best model in comparison with the others is the EGM2008, while the second best model is the EIGEN6C4.
{"title":"Evaluation of GGMs Based on the Terrestrial Gravity Disturbance and Moho Depth in Afar, Ethiopia","authors":"Eyasu Alemu","doi":"10.2478/arsa-2021-0007","DOIUrl":"https://doi.org/10.2478/arsa-2021-0007","url":null,"abstract":"Abstract To estimate Moho depth, geoid, gravity anomaly, and other geopotential functionals, gravity data is needed. But, gravity survey was not collected in equal distribution in Ethiopia, as the data forming part of the survey were mainly collected on accessible roads. To determine accurate Moho depth using Global Gravity Models (GGMs) for the study area, evaluation of GGMs is needed based on the available terrestrial gravity data. Moho depth lies between 28 km and 32 km in Afar. Gravity disturbances (GDs) were calculated for the terrestrial gravity data and the recent GGMs for the study area. The model-based GDs were compared with the corresponding GD obtained from the terrestrial gravity data and their differences in terms of statistical comparison parameters for determining the best fit GGM at a local scale in Afar. The largest standard deviation (SD) (36.10 mGal) and root mean square error (RMSE) (39.00 mGal) for residual GD and the lowest correlation with the terrestrial gravity (0.61 mGal) were obtained by the satellite-only model (GO_CONS_GCF_2_DIR_R6). The next largest SD (21.27 mGal) and RMSE (25.65 mGal) for residual GD were obtained by the combined gravity model (XGM2019e_2159), which indicates that it is not the best fit model for the study area as compared with the other two GGMs. In general, the result showed that the combined models are more useful tools for modeling the gravity field in Afar than the satellite-only GGMs. But, the study clearly revealed that for the study area, the best model in comparison with the others is the EGM2008, while the second best model is the EIGEN6C4.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"56 1","pages":"78 - 100"},"PeriodicalIF":0.9,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47233770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ayman Homda Mohamed, H. Dwidar, Inal Adham, A. Bakry, A. El-Raffie
Abstract In this paper, constrained minimization for the point of closest approach of two conic sections is developed. For this development, we considered the nine cases of possible conics, namely, (elliptic–elliptic), (elliptic–parabolic), (elliptic–hyperbolic), (parabolic–elliptic), (parabolic–parabolic), (parabolic–hyperbolic), (hyperbolic–elliptic), (hyperbolic–parabolic), and (hyperbolic–hyperbolic). The developments are considered from two points of view, namely, analytical and computational. For the analytical developments, the literal expression of the minimum distance equation (S) and the constraint equation (G), including the first and second derivatives for each case, are established. For the computational developments, we construct an efficient algorithm for calculating the minimum distance by using the Lagrange multiplier method under the constraint on time. Finally, we compute the closest distance S between two conics for some orbits. The accuracy of the solutions was checked under the conditions that L|solution ≤ ɛ1; G|solution ≤ ɛ2, where ɛ1,2 < 10−10. For the cases of (parabolic–parabolic), (parabolic–hyperbolic), and (hyperbolic–hyperbolic), we studied thousands of comets, but the condition of the closest approach was not met.
{"title":"Distance Between Two Keplerian Orbits","authors":"Ayman Homda Mohamed, H. Dwidar, Inal Adham, A. Bakry, A. El-Raffie","doi":"10.2478/arsa-2021-0006","DOIUrl":"https://doi.org/10.2478/arsa-2021-0006","url":null,"abstract":"Abstract In this paper, constrained minimization for the point of closest approach of two conic sections is developed. For this development, we considered the nine cases of possible conics, namely, (elliptic–elliptic), (elliptic–parabolic), (elliptic–hyperbolic), (parabolic–elliptic), (parabolic–parabolic), (parabolic–hyperbolic), (hyperbolic–elliptic), (hyperbolic–parabolic), and (hyperbolic–hyperbolic). The developments are considered from two points of view, namely, analytical and computational. For the analytical developments, the literal expression of the minimum distance equation (S) and the constraint equation (G), including the first and second derivatives for each case, are established. For the computational developments, we construct an efficient algorithm for calculating the minimum distance by using the Lagrange multiplier method under the constraint on time. Finally, we compute the closest distance S between two conics for some orbits. The accuracy of the solutions was checked under the conditions that L|solution ≤ ɛ1; G|solution ≤ ɛ2, where ɛ1,2 < 10−10. For the cases of (parabolic–parabolic), (parabolic–hyperbolic), and (hyperbolic–hyperbolic), we studied thousands of comets, but the condition of the closest approach was not met.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"56 1","pages":"57 - 77"},"PeriodicalIF":0.9,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43637565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract 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 root-mean-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.
{"title":"Performance Assessment of PPP-AR Positioning and Zenith Total Delay Estimation with Modernized CSRS-PPP","authors":"Omer Faruk Atiz, I. Kalaycı","doi":"10.2478/arsa-2021-0003","DOIUrl":"https://doi.org/10.2478/arsa-2021-0003","url":null,"abstract":"Abstract 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 root-mean-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.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"56 1","pages":"18 - 34"},"PeriodicalIF":0.9,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44666173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Janusz Zieliński, A. Świątek, P. Lejba, S. Oszczak
{"title":"In Memoriam: Dr. Eng. Leszek Jaworski (1961–2021)","authors":"Janusz Zieliński, A. Świątek, P. Lejba, S. Oszczak","doi":"10.2478/arsa-2021-0004","DOIUrl":"https://doi.org/10.2478/arsa-2021-0004","url":null,"abstract":"","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"56 1","pages":"35 - 36"},"PeriodicalIF":0.9,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41365516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Length-of-day (LOD) change, i.e., variations in Earth’s rotation rate, includes the long-term slowdown trend, as well as periodic and irregular fluctuations. The current continuous sequence of the LOD change covers a time span of <400 years. Using astronomical records in ancient historical documents, combined with a modern astronomical ephemeris, it is possible to obtain ancient LOD change. Some scholars have given a discontinuous LOD data series for the past 4000 years. In this paper, the author uses the Lomb–Scargle periodogram to study the LOD series and finds a significant quasi-1500-year-cycle signal. Furthermore, with weighted wavelet Z-transform, time-varying characteristics of the cycle in the LOD change are obtained.
{"title":"Quasi-1500-Year-Cycle Signal in Length-of-Day Change","authors":"Lihua Ma","doi":"10.2478/arsa-2021-0002","DOIUrl":"https://doi.org/10.2478/arsa-2021-0002","url":null,"abstract":"Abstract Length-of-day (LOD) change, i.e., variations in Earth’s rotation rate, includes the long-term slowdown trend, as well as periodic and irregular fluctuations. The current continuous sequence of the LOD change covers a time span of <400 years. Using astronomical records in ancient historical documents, combined with a modern astronomical ephemeris, it is possible to obtain ancient LOD change. Some scholars have given a discontinuous LOD data series for the past 4000 years. In this paper, the author uses the Lomb–Scargle periodogram to study the LOD series and finds a significant quasi-1500-year-cycle signal. Furthermore, with weighted wavelet Z-transform, time-varying characteristics of the cycle in the LOD change are obtained.","PeriodicalId":43216,"journal":{"name":"Artificial Satellites-Journal of Planetary Geodesy","volume":"56 1","pages":"10 - 17"},"PeriodicalIF":0.9,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47153241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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