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Guillaume Sébastien

Professeur HES associé

Hauptkompetenzen

Professeur HES associé

Telefon-Nummer: +41 24 557 23 17

Büro: D01

Haute école d'Ingénierie et de Gestion du Canton de Vaud
Route de Cheseaux 1, 1400 Yverdon-les-Bains, CH

Institut
insit - Institut d’ingénierie du territoire

BSc HES-SO en Géomatique - Haute école d'Ingénierie et de Gestion du Canton de Vaud

Méthodes d'estimation
Géodésie
Global Navigation Satellites Systems

2023

Drone with integrated moving baseline system and time-domain autofocus algorithm for high-resolution SAR images

Wissenschaftlicher Artikel ArODES

Peter Botzer, Daniel Henke, David Small, Emiliano Casalini, Sébastien Guillaume, Rolf Vogt, Elías Méndez Domínguez

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 17, 2360-2371

Link zur Publikation

Zusammenfassung:

The demand for drone-based synthetic aperture radar (SAR) systems is growing, especially for applications in cases where satellites or airborne systems are not sufficiently flexible. However, the combination of a long operating range and high spatial resolution causes the atmosphere to pose challenges for these systems. In this article, we present our K -band drone system that has a long range sensibility through modification to a commercially available radar. In addition, a moving baseline configuration has been integrated to ensure accurate attitude data, especially the heading. The desired spatial resolution is achieved by our proposed autofocus algorithm based on image sharpness. It is designed to also work in challenging cases of nonlinear flight paths and can be integrated into a processing framework based on back-projection. Several experiments were conducted to demonstrate the drone system's capabilities. These included a comparison with an established airborne radar: MIRANDA35. The obtained results demonstrate the ability of the drone SAR system to map wide areas at high spatial resolution.

Results from the third QDaedalus astrogeodetic system observation campaign in the mountainous terrain of the Surses region in Switzerland

Wissenschaftlicher Artikel ArODES

Muge Albayrak, Sébastien Guillaume, Daniel Willi, Christian Hirt, Ivan Dario Herrera Pinzon, Urs Marti, M. Tevfik Ozludemir, Lukas Müller, C. K. Shum

Journal of Surveying Engineering, 202023, vol. 149, no. 3

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Zusammenfassung:

This study presents the results of an astrogeodetic survey campaign conducted in the mountainous terrain of the Surses region in Switzerland. In our third astrogeodetic campaign using the QDaedalus system, we observed new deflections of the vertical (DoV) using three astrogeodetic systems. These observations were used to validate DoV data derived from the Global Gravity Model GGMplus and the Swiss Geoid model CHGeo2004. Astrogeodetic observations were conducted at 15 benchmarks (BMs) along the astrogeodetic profile over five nights in June 2021 at elevations ranging from 1,185 to 1,800 m and a station spacing of about 1 km. This is the first time two TS60 total station-based QDaedalus systems and one zenith telescope-based COmpact DIgital Astrometric Camera (CODIAC) system were used together for an astrogeodetic observation campaign. The standard deviations (SDs) of the QDaedalus system data for each session were 0.04″–0.22″ and 0.01″–0.20″ for the N–S and E–W components, respectively, while the SDs of the CODIAC system for each session were 0.02″ for both components. These high quality data were compared to DoV data derived from GGMplus and CHGeo2004. The N–S components from GGMplus exhibited large residuals ranging from −2.31′′ to 1.75″, while the E–W component residuals are from −0.27′′ to 1.80″. The residuals from CHGeo2004 range from −0.60 to 1.21 for the N–S components and −1.01 to 0.32 for the E–W components. These results show that the derived DoV data from CHGeo2004 are closer to the observed DoV and more accurate than the global GGMplus model that does not incorporate local gravity field data. The first and second astrogeodetic observation campaigns were conducted in the coastal terrain of Istanbul, Turkey and in the flat terrain in the Munich region, Germany, respectively. In this study, we provide an overall comparison of these previous results to the GGMplus residuals. Our latest results show that the GGMplus model is of higher quality in the Surses mountainous terrain than in the coastal terrain of Istanbul, while it is of lower quality than in the flat terrain of the Munich region.

Comparative measurements of astrogeodetic deflection of the vertical by latvian and swiss digital zenith cameras

Wissenschaftlicher Artikel ArODES

Inese Varna, Daniel Willi, Sébastien Guillaume, Müge Albayrak, Ansis Zarins, Mustafa Ozen

Remote Sensing, 15, 8, 2166

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Zusammenfassung:

Nowadays, zenith telescope-based digital zenith cameras (DZC), such as the COmpact DIgital Astrometric Camera (CODIAC) and VErtical by STArs (VESTA), are used to determine highly precise astrogeodetic deflections of the vertical (DoVs). The CODIAC and VESTA were developed by Eidgenossische Technische Hochschule (ETH) Zurich and University of Latvia, respectively, and only two CODIACs and four VESTAs were produced. The CODIAC has an established accuracy higher than 0.05″, while the accuracy of VESTA is ~0.1″. These two DZCs, which are the most used DZCs of the last decade, were used effectively over many survey campaigns. In this study, we used both the CODIAC and VESTA to conduct simultaneous observations at the School of Management and Engineering Vaud (HEIG-VD) in Yverdon-les-Bains, Switzerland, over five nights in August 2021. Our DZC measurements with CODIAC and VESTA mark the second time that simultaneous parallel observations were made with two different DZCs. Additionally, the VESTA was never tested against another DZC through comparative simultaneous measurements. These comparative measurements between the VESTA and CODIAC allowed for VESTA precision validation and checking the agreement between the two DZCs. The results of repeated, comparative DoV observations over five nights at HEIG-VD revealed a DoV measurement precision of VESTA around 0.13–0.16″ for 15 min long observation session and 0.10–0.13″ for 50 min long observation session. Mean DoV differences between CODIAC and VESTA at HEIG-VD were 0.08″ and −0.06″ for the North–South and East–West components, respectively.

2022

Optimization of safety critical IFR helicopter trajectories in alpine areas using MILP

Wissenschaftlicher Artikel ArODES

Evelyn Weiss, Sébastien Guillaume, Alain Geiger, Roland Hohensinn, Heinz Wipf

IEEE Transactions on Aerospace and Electronic Systems, 59, 2, 1127-1138

Link zur Publikation

Zusammenfassung:

Currently, helicopter operations according to Instrument Flight Rules (IFR) consist of high-altitude trajectories where the probability of collision with terrain is assumed to be very low. In such high altitudes, the risk of icing has to be considered, additionally, the flight time is unnecessarily long. Therefore, this paper elaborates on an optimization approach to find helicopter trajectories minimizing both flight time and height above terrain. To ensure safe operations, an iso-probability surface is calculated using collision probabilities, representing a surface above which the probability of collision with terrain is smaller than a chosen safety level. The optimization problem is solved using Mixed Integer Linear Programming (MILP). To evaluate the resulting trajectories the time until collision is evaluated for each waypoint, using a time-to-go approach based on Monte-Carlo simulations. The optimization with MILP yields feasible trajectories fulfilling a chosen safety level. Although the approach is computationally expensive, it serves as a basis for further research on these kinds of trajectory optimization applications.

Field comparison of the total station-based QDaedalus and the zenith telescope-based CODIAC astrogeodetic systems for measurements of the deflection of the vertical

Wissenschaftlicher Artikel ArODES

Müge Albayrak, Guillaume Willi, Sébastien Guillaume

Survey Review, 2022

Link zur Publikation

Zusammenfassung:

The precision and accuracy of a Leica MultiStation 60-based QDaedalus astrogeodetic measurement system are determined through observations at two locations in Switzerland. The precision of the QDaedalus was determined as 0.1″ for the N-S and E-W deflections of the verticals (DoVs) through 118 series of observations collected over 13 nights (in a 44-day observation period) at the HEIG-VD test station. The accuracy of the QDaedalus system was established by simultaneous parallel observations over two nights using the CODIAC system at the Zimmerwald Observatory. The differences between them were found to be 0.09″ and 0.02″ for the N-S and E-W DoV components, respectively. From these results, the accuracies of both DoV components can be interpreted as 0.1″. We also found a large systematic trend in the observed N-S DoV data at the HEIG-VD test station (0.008″/day). This study is the most extensive thus far for determining the precision and accuracy of the QDaedalus system for astrogeodetic measurements; it is also the first time that QDaedalus system’s accuracy has been established using parallel observations.

2021

Experimental validation of real-time ski jumping tracking system based on wearable sensors

Wissenschaftlicher Artikel ArODES

Johannes Link, Sébastien Guillaume, Bjoern M. Estkofier

Sensors, 2021, vol. 21, no. 23, pp. 1-16

Link zur Publikation

Zusammenfassung:

For sports scientists and coaches, its crucial to have reliable tracking systems to improve athletes. Therefore, this study aimed to examine the validity of a wearable real-time tracking system (WRRTS) for the quantification of ski jumping. The tracking system consists of wearable trackers attached to the ski bindings of the athletes and fixed antennas next to the jumping hill. To determine the accuracy and precision of the WRRTS, four athletes of the German A or B National Team performed 35 measured ski jumps. The WRRTS was used to measure the 3D positions and ski angles during the jump. The measurements are compared with camera measurements for the in-flight parameters and the official video distance for the jumping distance to assess their accuracy. We statistically evaluated the different methods using Bland–Altman plots. We thereby find a mean absolute error of 0.46 m for the jumping distance, 0.12 m for the in-flight positions, and 0.8°, and 3.4° for the camera projected pitch and V-style opening angle, respectively. We show the validity of the presented WRRTS to measure the investigated parameters. Thus, the system can be used as a tracking system during training and competitions for coaches and sports scientists. The real-time feature of the tracking system enables usage during live TV broadcasting.

2020

Astrojeodezide QDaedalus sistemi uygulamalari :

Wissenschaftlicher Artikel ArODES

bir inceleme

Müge Albayrak, Sébastien Guillaume

Harita Dergisi, 2021, vol. 165, pp. 73-89

Link zur Publikation

Zusammenfassung:

Öz:Astrogeodetic vertical deflections (VDs) data provide valuable information about the structure of Earth’s gravity field. To obtain astrogeodetic VDs at a point, the astronomic and geodetic coordinates (latitude and longitude) of this point need to be known. Currently, geodetic coordinates are obtained by dual-frequency GNSS receivers, while astronomical coordinates are obtained by the Digital Zenith Camera System (DZCS) or the total station-based QDaedalus system. Although DZCSs provide highly accurate (0.05″–0.1″) VDs data, the DZCSs are usually very expensive to construct and difficult to transport. For these reasons, researchers at ETH Zurich, a leading developer of astrogeodetic instruments, attempted to develop an alternative instrument to the DZCS: the QDaedalus system (accuracy ~0.2″). Unlike the DZCS, the QDaedalus system can be used for geodetic work during daytime. The QDaedalus system consists of a total station, a CCD camera, a mountable meniscus lens, a singlefrequency GNSS receiver and antenna, an interface box, and a laptop. In this paper, the QDaedalus system is presented in detail, and the methods for completing astrogeodetic observations and obtaining astrogeodetic VDs are explained. This paper also reviews all astrogeodetic studies conducted with the QDaedalus system from 2014–2019.

Almanya münih bölgesinde gözlemlenen astrojeodezik çekül sapma verilerinin, GGMplus ve EGM2008 global gravite alan modelleri ile karsilastirilmasi

Wissenschaftlicher Artikel ArODES

Müge Albayrak, Emel Zeray Öztürk, Ibrahim Öztug Bildirici, Christian Hirt, Sébastien Guillaume, CK Shum

Yerbilimleri/Hacettepe Üniversitesi Yerbilimleri Uygulama ve Arastirma Merkezi Dergisi = Yerbilimleri : Bulletin for Earth Sciences, 2020, vol. 41, no. 3, pp. 220-246

Link zur Publikation

Zusammenfassung:

Astrogeodetic vertical deflection (VD) data observed by astrogeodetic systems, which provide important information about Earth’s gravity field, are frequently used in the Earth Science disciplines, including geodesy and geophysics, to control and validate terrestrial, airborne and satellite gravity data. In this study, the total station-based QDaedalus system was used to observe astrogeodetic VD data at 10 benchmarks in the Munich region. The accuracy of these data is ~0.2 arcseconds (″). This high accuracy dataset was used to assess the quality of two global gravity field models—Global Gravitation Model Plus (GGMplus) and Earth Gravitational Model 2008 (EGM2008). The differences between the observed by QDaedalus and GGMplus-predicted VD data were ~0.2″ for both the North-South (N-S) and East-West (E-W) VD components, and reached a maximum of ~0.3″ and ~0.4″ for the N-S and E-W components, respectively. However, the maximum differences between the observed and EGM2008-predicted VD data for the N-S and E-W directions were 0.9″ and 1.8″, respectively. Thus, we found that the EGM2008-predicted values are less accurate than the predicted GGMplus values. The results of this study were compared with the results from a prior QDaedalus, and EGM2008 and GGMplus comparison study in Istanbul. In this article, we discuss the differences between the VD data obtained using the same QDaedalus system and global gravity field models in Istanbul and Munich, and explain the reasons for the higher accuracy of the VD data set predicted by GGMplus in both Munich and Istanbul.

Giant slalom :

Wissenschaftlicher Artikel ArODES

analysis of course setting, steepness and performance of different age groups — a pilot study

Björn Bruhin, Rowie J. F. Janssen, Sébastien Guillaume, Mara Gander, Felix Oberle, Silvio Lorenzetti, Michael Romann

Frontiers in Sports and Active Living, 2020, vol. 2

Link zur Publikation

Zusammenfassung:

Introduction: Giant slalom is the core discipline of alpine skiing, and each race has its own specific course and terrain characteristics. These variations may explain differences in the speed and time per turn profiles, which are essential for performance development and injury prevention. This study aims to address the differences in course setting and steepness of the different course sections (flat—medium—steep) and compare them to the performance parameters among young (U12, U14, U16) and older (U18, U21, elite) male athletes. Methods: The study examined a total sample size of 57 male athletes; 7 from elite level, 11 from U21, 13 from U18, 6 from U16, 13 from U14, and 7 from U12. The athletes wore a portable global navigation satellite system (GNSS) sensor to extract performance parameters. The course profiles and gate positions of nine runs were measured with differential GNSS. The runs were divided into flat, medium and steep sections. From the performance parameters (speed, time per turn, etc.) and the course setting variables, the mean value per section was calculated and used for the further analysis. Results: In total, 192 run sections from 88 runs were recorded and analyzed. Comparisons between course settings in young and older classes showed no significant differences. However, the turning angles and horizontal gate distances were smaller in flat sections. Average speed (49.77 vs. 65.33 km/h) and time per turn (1.74 vs. 1.41 s) differed significantly between young and U21/elite categories. In medium terrain sections U21 and elite athletes spent more time in the gliding phase compared to all other athletes. Discussion: It seems to be a reasonable that, given similar course setting and steepness, speed increases concurrently with the technical and tactical skills of the athlete. Moreover, the finding that the elite athletes spent more time in the gliding phase could be crucial for understanding technique and performance development in young athletes.

Quality assessment of global gravity field models in coastal zones: A case study using astrogeodetic vertical deflections in Istanbul, Turkey

Wissenschaftlicher Artikel ArODES

Müge Albayrak, Christian Hirt, Sébastien Guillaume, Kerem Halicioglu, M. Tevfik Özlüdemir, C. K. Shum

Studia Geophysica et Geodaetica, 2020, vol. 64, pp. 306-329

Link zur Publikation

Zusammenfassung:

We present the first high-precision astrogeodetic vertical deflection (VD) observations collected in Istanbul, Turkey, using a novel lightweight total station integrated with a charge-coupled device (CCD) camera, the QDaedalus system. The observed VDs are unique in that, they were measured for the first time in Istanbul, and they form Turkey’s first dense astrogeodetic network. To establish the Istanbul Astrogeodetic Network (IAN), we selected 30 benchmarks (BMs) with known geodetic coordinates. A total of 21 of these BMs are located in the coastal zone allowing us to investigate the quality of global gravity field models (GGFMs) along the coast of Istanbul. The standard deviations for our VDs are approximately ±0.20″which is commensurate with the VD accuracy of early studies assessing the QDaedalus observations. In particular, dedicated comparison measurements were conducted in two geographic regions—Munich and Istanbul—to control the accuracy of the VD measurements. Our new VD data set within the IAN was compared with predicted VDs from the Global Gravity Model plus (GGMplus) and the Earth Gravitational Model 2008 (EGM2008). The VD residuals between the QDaedalus observations, and predicted values from GGMplus and EGM2008 models tend to increase towards the coastlines, where discrepancies of several arcseconds were found. At 15 coastal BMs, the residuals in the N-S components exceed 2″ and reach values as large as 6″ while residuals in the E-W components exceeded 2″ at 3 BMs. We interpret these large differences as an indication of the current weaknesses in the GGF Ms, most likely reflecting errors in the altimetry-derived marine gravity measurements, which have been incorporated in the EGM2008 and GGMplus models, or the lack of coastal terrestrial gravity measurements, or both. We conclude that the astrogeodetic VDs observed by the QDaedalus are invaluable for independently assessing the quality of coastal-zone terrestrial gravity data sets and GGFMs.

2022

A GPS moving baseline navigation system on a SAR DRONE tested in an experiment to analyze the signature of covered reflectors

Konferenz ArODES

Peter Brotzer, Daniel Henke, Sébastien Guillaume

Proceedings of the IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium

Link zur Konferenz

Zusammenfassung:

The miniaturization of frequency-modulated continuous-wave synthetic aperture radar systems has become increasingly important in recent years. In this paper, we present the ongoing improvements on our SAR drone hardware setup, with special focus on the integration of moving baseline aided navigation data. Furthermore, an experiment investigates the detection of covered reflectors, determines the attenuation factor, and demonstrates the advantages of moving baseline supported processing.

Quantification of the dependence of the results on several network adjustment applications

Konferenz ArODES

Stéphane Durand, Michael Lösler, Mark Jones, Paul-Henri Cattin, Sébastien Guillaume, Laurent Morel

Proceedings of the 5th Joint International Symposium on Deformation Monitoring (JISDM)

Link zur Konferenz

Zusammenfassung:

The dependency of the results from a network adjustment on the application used is investigated. For that purpose, the results obtained by each tested application on several sets of simulated measurements are compared. In each simulation, only one parameter varies. We first present our comparison methodology and the method that was used to add Gaussian-like errors to theoretical measurements. We then apply it to study the impact of the side length of the network and of the ellipsoidal height difference among points in the network for several network adjustment applications: Columbus, CoMeT, Geolab, JAG3D, LGC, Move3, Star*Net and Trinet+.

2021

Testing two different QDaedalus systems under similar conditions at Geodetic Observatory Wettzell and Technical University of Munich, Germany

Konferenz ArODES

Müge Albayrak, Christian Hirt, Sébastien Guillaume, Thomas Klügel

Proceedings of the 21st SGEM International Multidisciplinary Scientific GeoConference 2021

Link zur Konferenz

Zusammenfassung:

QDaedalus systems are currently used for astronomical observations to obtain astrogeodetic vertical deflections (VDs). Astronomical observations cannot be made under the same conditions as geodetic observations (e.g., GNSS), because meteorological factors (e.g., cloud cover during observation, high humidity, fog, etc.) and timing of the observations may directly affect the observed benchmarks, particularly regarding precision and accuracy determinations of the VD components observed with the QDaedalus system. For this reason, we tested Leica TCRM1101 and TDA5005 total station (TS)-based QDaedalus systems at the Geodetic Observatory Wettzell (GOW) and the Technical University of Munich (TUM) astrogeodetic control station, using the same benchmarks for each device. While 4 benchmarks at GOW were used over a 2-day period (August 11-13, 2018), the TUM control station was used over three different nights (July 19, 20 and 28, 2018). The standard deviations for TCRM1101 and TDA5005 at GOW and TUM are ~0.2" or less for both of the components. While the differences between the two systems at GOW are ~0.3" or smaller for the N-S VD components, differences for the E-W components only exceed 0.3" at one of the four benchmarks. At TUM, the differences between the two systems are smaller than 0.2" for both components. Overall, these comparisons at GOW and TUM show the results from the two systems to be in good agreement. Additionally, the TUM control station has been used to test these TSs on different nights: 9 nights (TCRM1101) and 15 nights (TDA5005). The results obtained from these measurements under similar conditions at TUM by two systems were compared with other results at TUM, and subsequently, all the results are discussed.

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Guillaume Sébastien

Professeur HES associé

Hauptkompetenzen

Géodésie

GNSS

Méthodes d'estimation

Navigation

Réalité virtuelle

Professeur HES associé

PEOPLE@HES-SO Verzeichnis der Mitarbeitenden und Kompetenzen

Guillaume Sébastien

Professeur HES associé

Hauptkompetenzen

Géodésie

GNSS

Méthodes d'estimation

Navigation

Réalité virtuelle

Professeur HES associé

PEOPLE@HES-SO
Verzeichnis der Mitarbeitenden und Kompetenzen