Estimation and Validation of multi-GNSS multi-Frequency Phase Center Corrections

verfasst von: Johannes Kröger
betreut von: Steffen Schön
Abstract: For highly accurate and precise positioning, navigation, and timing based on Global Navigation Satellite System (GNSS) signals, it is essential to consider Phase Center Corrections (PCC). Typically, GNSS processing estimates coordinates that refer to an easily accessible point, usually the antenna’s substructure, known as the Antenna Reference Point (ARP). However, GNSS carrier-phase measurements relate to the electronic reception point, which varies based on the azimuth and elevation angles of incoming satellite signals and differs between antenna models, types, and frequencies. Corrections, which consider the differences between the ARP and the electronic receiving point, are required in order to achieve precise positioning. These corrections, known as PCC, can be determined in an anechoic chamber using artificially generated signals or in the field using a robot and real signals. In the past, the accuracy and precision of multi-GNSS, multi-frequency positioning were degraded due to the lack of robot-based PCC for newer signals and systems.

This thesis presents the successful estimation of multi-GNSS, multi-frequency PCC using a robot and real GNSS signals. A key innovation of this work is the parameterization of PCC using an adapted version of hemispherical harmonic functions, as opposed to the commonly used spherical harmonic functions. This advancement ensures a stable normal equation system and enables the calculation of reasonable formal errors for the estimated PCC.

A clear and standardized strategy for comparing PCC sets is still lacking. In response, various strategies for comparing different PCC sets are presented using both simulated and real difference patterns. Based on these analyses, the benefits and challenges of each strategy are discussed. Characteristic values for assessing the similarity of PCC sets are introduced, and a standardized simulation approach is developed. This approach allows for the assessment of the impact of ΔPCC on geodetic parameters, such as topocentric coordinate differences, receiver clock error, and tropospheric parameters. Comparisons with common strategies using real data demonstrate that the developed approach is thorough and efficient, representing a substantial step toward standardizing the comparison of different PCC sets.

To identify the specific causes limiting the higher repeatability of PCC estimation and to understand why discrepancies between different calibration facilities occur, a thorough evaluation of specific steps and processing parameters within the antenna calibration procedure is conducted. The analysis reveals that the quality of observations, rather than differences in observation distribution on the antenna hemisphere, has the greatest influence on the repeatability of PCC estimation.

The thesis also addresses the challenges of independently validating PCC within the observation domain, particularly due to predominant error sources such as multipath (MP) effects. It is demonstrated that different PCC sets can be validated by applying them to Single Differences (SD) in a short baseline, common clock setup. Applying PCC estimated with the developed algorithm to uncorrected SD time series shows mean improvements in standard deviations up to 1.33%. The overall magnitude of these improvements is relatively small because of the application of an accurate a priori Phase Center Offset (PCO) to the uncorrected SD to prevent large drifts. Also, other remaining error sources complicate the validation process. Thus, a new approach for validating PCC, based on time-differenced SD using a calibration process, has been proposed. Initial results are promising, showing mean improvements in the standard deviation of the dSD time series of up to 8%.
Organisationseinheit(en): Institut für Erdmessung
Typ: Dissertation
Anzahl der Seiten: 192
Publikationsdatum: 01.09.2025
Publikationsstatus: Veröffentlicht
ASJC Scopus Sachgebiete: Ingenieurwesen (sonstige)
Fachgebiet (basierend auf ÖFOS 2012): Geodäsie
Ziele für nachhaltige Entwicklung: SDG 9 – Industrie, Innovation und Infrastruktur
Elektronische Version(en): https://doi.org/10.15488/19452 (Zugang: Offen)
: Details im Forschungsportal „Research@Leibniz University“

BibTeX

@phdthesis{d325fab19dd04277a6adb8cf658cb946,
title = "Estimation and Validation of multi-GNSS multi-Frequency Phase Center Corrections",
abstract = "For highly accurate and precise positioning, navigation, and timing based on Global Navigation Satellite System (GNSS) signals, it is essential to consider Phase Center Corrections (PCC). Typically, GNSS processing estimates coordinates that refer to an easily accessible point, usually the antenna{\textquoteright}s substructure, known as the Antenna Reference Point (ARP). However, GNSS carrier-phase measurements relate to the electronic reception point, which varies based on the azimuth and elevation angles of incoming satellite signals and differs between antenna models, types, and frequencies. Corrections, which consider the differences between the ARP and the electronic receiving point, are required in order to achieve precise positioning. These corrections, known as PCC, can be determined in an anechoic chamber using artificially generated signals or in the field using a robot and real signals. In the past, the accuracy and precision of multi-GNSS, multi-frequency positioning were degraded due to the lack of robot-based PCC for newer signals and systems.This thesis presents the successful estimation of multi-GNSS, multi-frequency PCC using a robot and real GNSS signals. A key innovation of this work is the parameterization of PCC using an adapted version of hemispherical harmonic functions, as opposed to the commonly used spherical harmonic functions. This advancement ensures a stable normal equation system and enables the calculation of reasonable formal errors for the estimated PCC.A clear and standardized strategy for comparing PCC sets is still lacking. In response, various strategies for comparing different PCC sets are presented using both simulated and real difference patterns. Based on these analyses, the benefits and challenges of each strategy are discussed. Characteristic values for assessing the similarity of PCC sets are introduced, and a standardized simulation approach is developed. This approach allows for the assessment of the impact of ΔPCC on geodetic parameters, such as topocentric coordinate differences, receiver clock error, and tropospheric parameters. Comparisons with common strategies using real data demonstrate that the developed approach is thorough and efficient, representing a substantial step toward standardizing the comparison of different PCC sets.To identify the specific causes limiting the higher repeatability of PCC estimation and to understand why discrepancies between different calibration facilities occur, a thorough evaluation of specific steps and processing parameters within the antenna calibration procedure is conducted. The analysis reveals that the quality of observations, rather than differences in observation distribution on the antenna hemisphere, has the greatest influence on the repeatability of PCC estimation.The thesis also addresses the challenges of independently validating PCC within the observation domain, particularly due to predominant error sources such as multipath (MP) effects. It is demonstrated that different PCC sets can be validated by applying them to Single Differences (SD) in a short baseline, common clock setup. Applying PCC estimated with the developed algorithm to uncorrected SD time series shows mean improvements in standard deviations up to 1.33%. The overall magnitude of these improvements is relatively small because of the application of an accurate a priori Phase Center Offset (PCO) to the uncorrected SD to prevent large drifts. Also, other remaining error sources complicate the validation process. Thus, a new approach for validating PCC, based on time-differenced SD using a calibration process, has been proposed. Initial results are promising, showing mean improvements in the standard deviation of the dSD time series of up to 8%.",
keywords = "multi-GNSS-Prozessierung, PCC-Validierungsstrategien, Hemisph{\"a}rische Harmonische, Absolute GNSS-Antennenkalibrierung, PCC, Multi-GNSS Processing, PCC Validation Strategies, Hemispherical Harmonics, Absolute GNSS Antenna Calibration, PCC",
author = "Johannes Kr{\"o}ger",
year = "2025",
month = sep,
day = "1",
doi = "10.15488/19452",
language = "English",
isbn = "978-3-7696-5376-2",
series = " Wissenschaftliche Arbeiten der Fachrichtung Geod{\"a}sie und Geoinformatik der Leibniz-Universit{\"a}t Hannover",
publisher = "Fachrichtung Geod{\"a}sie und Geoinformatik der Leibniz Universit{\"a}t Hannover",
school = "Leibniz University Hannover",
}