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1

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.

2

An example and analysis for ambiguity resolution in the indoor ZigBee positioning system

Janicka J., Rapinski J.

Reports on Geodesy and Geoinformatics

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2017

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Vol. 103

1--9

EN

This paper presents ambiguity resolution in the range-based ZigBee positioning system. The system is using the phase shift measurements to determine the distances between user and anchors. In this paper, the ambiguity is defined as the number of full reps of a certain distance added to the measurement result. The way of resolving ambiguities in the positioning system is described and an experiment results are presented. Featured algorithm is successful in finding ambiguities and correct location of the user.

3

On-the-fly ambiguity resolution using an estimator of the modified ambiguity covariance matrix for the GNSS positioning model based on phase data

Cellmer S.

Artificial Satellites : Journal of Planetary Geodesy

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2012

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Vol. 47, No. 3

81--90

EN

On-the-fly ambiguity resolution (OTF AR) is based on a small data set, obtained from a very short observation session or even from a single epoch observation. In these cases, a classical approach to ambiguity resolution (e.g. the Lambda method) can meet some numerical problems. The basis of the Lambda method is an integer decorrelation of the positive definite ambiguity covariance matrix (ACM). The necessary condition for the proper performing of this procedure is a positive definiteness of ACM. However, this condition is not satisfied in cases of very short observation sessions or single epoch positioning if phaseonly observations are used. The subject of this contribution is such a case where phase-only observations are used in the final part of the computational process. The modification of ACM is proposed in order to ensure its positive definiteness. An estimator of modified ACM is a good ACM approximation for the purpose of performing the LAMBDA method. Another problem of short sessions (or a single epoch) positioning is the poor quality of the float solution. In this paper, a cascade adjustment with wide-lane combinations of signals L1 and L2 as a method of solving this problem is presented.

4

Study on GPS phase ambiguity resolution effectiveness with use of LAMBDA de-correlation method

Skorupa B.

Geomatics and Environmental Engineering

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2011

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Vol. 5, no. 2

81-87

EN

Results of numerical tests focused on application of the LAMBDA de-correlation method for calculation of cycle ambiguities in GPS phase measurement, have been presented. The calculations were made for observations within the band L1, registered in short, static measurement sessions. Correctness of the de-correlation method algorithm was tested on the basis of model sets of initial ambiguities of phase cycles in double differences, which were calculated with the assumption that GPS vector coordinates were not changed. Verification of the ambiguities was conducted using Integer Search Ratio test. Influence of the de-correlation method on size of search space of optimal ambiguity sets, was also examined. Moreover, comparison of the LAMBDA method effectiveness with classic algorithm used for calculation of phase cycle ambiguities in GPS measurements, was also presented. The testing calculations were conducted with use of RBS program developed in the Department of Geomatics of the University of Science and Technology in Krakow – Poland, as well as with use of the software from Internet NGS (National Geodetic Survey) service.

PL

W pracy zaprezentowano wyniki testów numerycznych, dotyczących zastosowania metody dekorelacyjnej LAMBDA (Least Squares Ambiguity Decorrelation Addjustment) do wyznaczenia nieoznaczoności cykli w pomiarach fazowych GPS. Obliczenia wykonano dla obserwacji w paśmie L1, zarejestrowanych w krótkich, statycznych sesjach pomiarowych. Poprawność działania algorytmu metody dekorelacyjnej badano na podstawie wzorcowych zestawów całkowitych początkowych nieoznaczoności cykli fazowych w drugich różnicach, obliczonych przy założeniu niezmienności współrzędnych wektora GPS. Weryfikację rozwiązania nieoznaczoności przeprowadzono za pomocą testu Integer Search Ratio. Przedmiotem badań był również wpływ metody dekorelacyjnej na wielkość przestrzeni poszukiwań optymalnych zestawów nieoznaczoności. Ponadto przedstawiono porównanie efektywności metody LAMBDA i klasycznego algorytmu wyznaczania nieoznaczoności cykli fazowych w pomiarach GPS. Obliczenia testowe zrealizowano przy użyciu programu RBS opracowanego w Katedrze Geomatyki WGGiIŚ AGH oraz oprogramowania udostępnionego w serwisie internetowym NGS (National Geodetic Survey).

5

Wyznaczenie współrzędnych osnowy szczegółowej GPS III powiatu wieruszowskiego

Bakuła M., Oszczak S., Baryła R., Popielarczyk D., Jarmołowski W., Tyszko A., Oszczak B., Sitnik E., Gregorczyk R., Wielgosz P., Rapiński J., Jesiotr G.

Geomatics and Environmental Engineering

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2007

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Vol. 1, no. 1/1

43-52

PL

W pracy przedstawiono metodykę pomiaru i opracowania osnowy szczegółowej GPS III na obszarze powiatu wieruszowskiego. Pomiary 988 punktów wykonano metodą statyczną w ciągu dziesięciu dni z wykorzystaniem 12 odbiorników GPS Ashtech Z-XII, Z-Surveyor, Z-Xtreme. W pracy przedstawiono także analizy wyrównania i transformacji z układu ETRF-89 do państwowych układów współrzędnych: "1965" i "2000". Z uwagi na liczne zasłony drzew nad wyznaczanymi punktami, obserwacje GPS powtórzono na około trzydziestu punktach, aby uzyskać wymaganą dokładność i niezależną kontrolę pomiarów. Dodatkowo przy takiej liczbie odbiorników bardzo skuteczne okazały się analizy zamknięć przyrostów w trójkątach jak również warunki geometryczne nieoznaczoności pomiarów fazowych stosowane przy rozwiązaniach multistacyjnych.

EN

The paper presents the methodology of GPS measurements and data elaboration for control points in the Wieruszów District area. GPS measurements of 988 points were executed with the use of static method during ten days of measurements and twelve GPS receivers of Ashtech company i.e. Z-XII, Z-Surveyor, Z-Xtreme. The results and analyses of adjustment and transformation from ETRF-89 to the national coordinate systems: ,,1965" and ,,2000" were also presented. Due to bad observational conditions of GPS measurements there were about thirty points on which GPS measurements were repeated in order to achieve reliable and accurate results. Additionally, loop closures of baselines and geometric conditions of ambiguity network solutions were successfully useful before final adjustment.

6

Wyznaczenie drugoróżnicowych całkowitoliczbowych nieoznaczoności cykli w pomiarach fazowych GPS zarejestrowanych na punktach lokalnej sieci stacji permanentnych

Skorupa B.

Geomatics and Environmental Engineering

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2007

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Vol. 1, no. 1/1

213-221

PL

Estymację lokalnych różnicowych modeli refrakcji poprzedza się wstępnym opracowaniem pomiarów fazowych zarejestrowanych w sieci stacji permanentnych GPS, w celu wyznaczenia całkowitoliczbowych początkowych nieoznaczoności cykli fazowych. Proces obliczeniowy można uprościć, zakładając stałość współrzędnych końców wektorów GPS. Założenie takie można poczynić, ponieważ współrzędne geodezyjne stacji permanentnych są wyznaczane z wysoką precyzją w danym jednolitym układzie odniesienia. W niniejszej pracy zaprezentowano algorytm oraz przykłady numeryczne wyznaczenia wartości całkowitoliczbowych początkowych nieoznaczoności cykli fazowych w drugich różnicach, przy założeniu stałości współrzędnych końców wektora GPS. Efektywność rozwiązania nieoznaczoności analizowano w oparciu o wartości ilorazu Integer Search Ratio. Obliczenia zrealizowano przy użyciu programów opracowanych w Zakładzie Geodezji i Kartografii WGGilŚ AGH oraz programu firmowego AOS v. 1.6. W eksperymentach obliczeniowych użyto pomiarów fazowych GPS zarejestrowanych na punktach aktywnej sieci geodezyjnej ASG-PL.

EN

Geodetic coordinates of GPS permanent stations are calculated with high precision, in given homogeneous reference frame. There is an requirement for elaborating the measurements collected on points of permanent stations, for integer phase ambiguity resolution. Next, this ambiguities are used in estimation process of local differential refraction models. The paper presents a method for determining double difference integer phase ambiguity, with assumption of constant GPS vector coordinates. The efficiency of ambiguity resolution was analysed at use of Integer Search Ratio. Quoted numerical examples were realized at use of the computer programs made in Department of Geodesy and Cartography at the AGH University of Science and Technology and AOS v. 1.6 software. In computational experiments phase measurements were performed on points of active geodetic network ASG-PL.

7

Sensitivity of ADOP to changes in the single-baseline GNSS model

Odijk D., Teunissen P. J. G.

Artificial Satellites : Journal of Planetary Geodesy

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2007

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Vol. 42, No. 2

71--96

EN

The ADOP (Ambiguity Dilution Of Precision) is a measure for the precision of the carrier phase ambiguities involved in precise relative GNSS positioning. By computing the ADOP one may get knowledge in whether ambiguity resolution can be expected successful or not, already in a stage before the GNSS data are collected. In Odijk and Teunissen (2008) compact closed-form expressions have been derived for the ADOP of single-baseline GNSS models. In this paper these expressions are used to study the impact of certain changes in these models, as there are the observation time span, the weighting of the ionospheric delays, the number of frequencies, the weights of the phase and code data, the number of satellites, elevation-dependent observation weights and taking linear combinations of data.

8

Analiza precyzji i dokładności pomiarów GPS w warunkach leśnych

Bakuła M., Oszczak S., Pelc-Mieczkowska R., Suchocki M., Chrostowska M., Rudziński M.

Roczniki Geomatyki

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2006

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T. 4, z. 3

23-32

EN

The paper presents results of GPS measurements executed in forest conditions. The GPS measurements were made with the use of dual-frequency Ashtech Z-Xtreme receivers. The test measurements were performed in the forest at the University of Warmia and Masury in Olsztyn. Two different analyses were conducted: Real Time Positioning (RTK) and post-processing data elaboration. Postprocessing GPS data were elaborated with the use of Ashtech Office Suite (AOS) software. After very careful study of static elaborations centimeter accuracy was achieved, though large errors (a few meters) could occur. Gross errors were caused by heavy obstructions due to tree canopy. It caused frequent losses of contact with satellites as well as multipath errors. Similarly in the case of RTK measurements thanks to multiple initialization of ambiguity resolution centimeter accuracy was also obtained. However, GPS/RTK measurements demand large experience in GPS elaboration as well as very thorough knowledge of GPS positioning. Very important issue is careful planning of GPS sessions as well as applying appropriate GPS receiver sets. Future combination of GPS and GLONASS with GALILEO systems will bring considerable improvement in getting reasonable results in forest conditions, especially RTK positioning seems very costeffective in forest conditions.

9

Impact of tec fluctuations in the Antarctic ionosphere on GPS positioning

Krankowski A., Shagimuratov I. I.

Artificial Satellites : Journal of Planetary Geodesy

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2006

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Vol. 41, No. 1

43--56

EN

With increasing reliance on space-based platforms for global navigation and communication, concerns about the impact of ionospheric scintillation and total electron content fluctuations on these systems have became a high priority. In this paper, GPS transionospheric signals have been used to study the development of ionospheric phase fluctuations observed at Antarctic IGS permanent stations: McMurdo-MCM4, Casey-CAS1, Mawson-MAW1, Sanae-VESL, Syowa-SYOG and Davis-DAV1 in 2001. The use of the multi-station, multi-path observations of the GPS beacons has allowed the study of the time development of irregularities as a function of latitude and longitude of individual geomagnetic storms. The basic storms studied were those of March 19-20, March 31, April 9-11, June 16-17, and September 23, 2001. The rate of TEC (ROT) parameter was used to study the occurrence of TEC fluctuations. The results from studying these storms showed the unique nature of each storm. For the above five storms, data were available from three auroral stations (VESL, SYOG and MAW1) and from 61° to 70° Corrected Geomagnetic Latitude (CGL). In addition, data from three higher latitude polar stations (DAV1, MCM4 and CAS1) near 800 CGL are also analysed. Fluctuation effects, causing dramatic changes in total electron content – TEC, can have a different impact on GPS positioning accuracy (especially during phase ambiguity resolution). Bernese ver.4.2 software was used for the analysis of the GPS permanent data from Antarctic IGS stations. The analyses rely on studying the repeatability of vector co-ordinates. These vectors were investigated during the geomagnetic storms when the intensity of TEC fluctuations was more pronounced. The impact of TEC fluctuations in the high latitude ionosphere on GPS positioning accuracy has been discussed in terms of the total number of observations of doubledifferences (DD) and in the ratio of the total number of all ambiguities to unresolved ones.