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1

PPP using Galileo-only observation in receiver antenna PCC aspect

100%

Dawidowicz K.

GIS Odyssey Journal

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2024

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tom Vol. 4, no. 1

5--24

EN

Besides the Global Positioning System (GPS) and Globalnaya Navigatsionnaya SputnikovayaSistema (GLONASS), two additional global navigation satellite systems (GNSS) have reached full operational capability in recent years. The European Union, along with the European Space Agency, introduced the Galileo positioning system. China is developingthe BeiDou system. To fully utilize the capabilities of the new systems, dedicated precise models and corrections are necessary. An example of such corrections can be antenna phase center corrections (PCC). In the case of Galileo, access to phase center corrections may be challenging. This is because a lot of GNSS antenna types still have no corrections directly dedicated to Galileo signals. In such a case, corrections created based on GPS signals are recommended. The study compared the positions of stations, determined based on Galileo-only observations using type-mean and individual PCC models obtained from field and anechoic chamber calibration. Additionally, calculations were performed using elevation-only PCC based on the type-mean model. It was demonstrated that position shifts resulting from the use of individual PCC derived from an out-door calibration instead of individual calibration in an anechoic chamber (dedicated PCC set for Galileo signals) can reach up to 5 mm in the vertical component, whilefor horizontal components, these shifts are generally less than 2 mm.

2

GNSS antenna caused near-field interference effect in precise point positioning results

63%

Dawidowicz K. , Baryła R. B.

Artificial Satellites : Journal of Planetary Geodesy

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2017

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tom Vol. 52, No. 2

27--40

EN

Results of long-term static GNSS observation processing adjustment prove that the often assumed "averaging multipath effect due to extended observation periods" does not actually apply. It is instead visible a bias that falsifies the coordinate estimation. The comparisons between the height difference measured with a geometrical precise leveling and the height difference provided by GNSS clearly verify the impact of the near-field multipath effect. The aim of this paper is analysis the near-field interference effect with respect to the coordinate domain. We demonstrate that the way of antennas mounting during observation campaign (distance from nearest antennas) can cause visible changes in pseudo-kinematic precise point positioning results. GNSS measured height differences comparison revealed that bias of up to 3 mm can be noticed in Up component when some object (additional GNSS antenna) was placed in radiating near-field region of measuring antenna. Additionally, for both processing scenario (GPS and GPS/GLONASS) the scattering of results clearly increased when additional antenna crosses radiating near-field region of measuring antenna. It is especially true for big choke ring antennas. In short session (15, 30 min.) the standard deviation was about twice bigger in comparison to scenario without additional antenna. When we used typical surveying antennas (short near-field region radius) the effect is almost invisible. In this case it can be observed the standard deviation increase of about 20%. On the other hand we found that surveying antennas are generally characterized by lower accuracy than choke ring antennas. The standard deviation obtained on point with this type of antenna was bigger in all processing scenarios (in comparison to standard deviation obtained on point with choke ring antenna).

3

Analysis of comparability of PCV in surveying-grade GNSS antenna - Topcon HIPER-VR case study

63%

Baryła R. , Dawidowicz K.

Artificial Satellites : Journal of Planetary Geodesy

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2024

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tom Vol. 59, No. 3

87--99

EN

It is well known that the phase center of a Global Navigation Satellite System (GNSS) antenna is not a stable point. For any given GNSS antenna, the phase center will change with the direction of the incoming signal from a satellite, as well as the frequency. Ignoring these phase center variations (PCVs) in GNSS data processing can lead to notable errors, especially in vertical position component determination. To avoid the problem, antenna PCV together with the phase center offset (PCO) information are recommended to be used in GNSS observation processing. We currently distinguish between individual and type-mean phase center correction (PCC) models. These models describe the variations in the phase center of the antenna as a function of the elevation angle and azimuth. In general, the primary difference between individual and type-mean models lies in their specificity. Individual models are highly precise but are valid only for a particular antenna model, while the type-mean models are more general and can be applied to a broad range of antennas of the same type, but may suffer from a lower level of precision. This paper aims to analyze the comparability of PCV in surveyinggrade GNSS antennas. For the analyses, we propose to use an originally designed bench with precisely defined relative positions of the seven antenna mounting points. Preliminary studies have been performed using GPS observations on L1 and L2 frequencies recorded by seven Topcon HIPER-VR antennas. The results proved that the comparability of PCV for this antenna is high. The position error did not exceed 3 mm. It could be assumed that the type-mean PCC model could describe PCV all antennas of this type with good accuracy.