Personne :
Santerre, Rock

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Université Laval. Département des sciences géomatiques
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Voici les éléments 1 - 10 sur 58
  • Publication
    A sequential network approach for estimating GPS satellite phase biases at the PPP-AR producer-side
    (Springer, 2018-04-11) Santerre, Rock; Kamali, Omid; Cocard, Marc
    Ambiguity resolution (AR) in precise point positioning (PPP) requires precise satellite orbit, clocks, and phase biases corrections. Satellite phase biases are fractional hardware corrections which help to retrieve the un-differenced integer carrier phase ambiguities. Satellite corrections can be obtained from the international GNSS service (IGS) or estimated by correction providers called producer-side. We introduce a new PPP-AR observation model and a new sequential network algorithm (SNA) to estimate satellite phase biases. The new model is fully compatible with standard IGS satellite correction products, and it takes advantage of currently available IGS global ionosphere maps to improve the stability of corrections estimation. Furthermore, the proposed model is full-rank per-frequency and per-site and this method simplifies the integration of any additional frequency or site observables in the system of equations. The per-site satellite phase biases method allows users to customize their network solution. In many cases, users only have to estimate the phase biases of a few satellites estimated by few stations to resolve ambiguities of their observed satellites. The novel two-step algorithm provides a good balance between the computational burden, the computer memory load, the efficiency of handling parameters, and the precise estimation of correction parameters. The proposed PPP-AR model and the SNA performance is then validated by estimating satellite phase biases with 1 year of GPS data from a sub-network of IGS stations. A rigorous a posteriori statistical test is performed using data from an independent GPS network. As a result, the precision of WL and L1 ambiguities was improved significantly with the confidence level of P > 99.99% by applying the estimated phase bias corrections to phase observables.
  • Publication
    Movements of the Quebec bridge's suspended span measured by GNSS technology
    (Canadian Institute of Geomatics., 2016-12-01) Santerre, Rock; Bourgon, Stéphanie.; Smadi, Youssef
    The Quebec Bridge was completed in 1917 and it is still the longest cantilever bridge in the world. Overall, the actual movements of its suspended span, as detected by GNSS (between 2012 and 2013), are in fair agreement with the original design calculations: for the train loading effect on the vertical movement (17 cm for one freight train); the transversal wind load effect on the transversal movement (32 cm for a wind speed of 170 km/h); and the temperature loading effect on the ver ti cal movement of the suspended span (3.2 cm for a 50°C temperature variation). Further movements have been detected by GNSS technology, namely: the transversal and longitudinal movements of the suspended bridge span due to train passages (11 cm transversally, at the top of the suspended span, and 1 cm longitudinally); the transversal movement of the bridge caused by solar radiation (differential) conditions on both sides of the bridge (5 cm for high solar radiation values); and the longitudinal movement of the suspended span of the Quebec Bridge at temperatures lower than 6°C (7 cm to −25°C).
  • Publication
    Geometry of GPS relative positioning
    (Springer Link, 2018-02-24) Santerre, Rock; Geiger, Alain
    GPS positioning is often assimilated to trilateration and even to triangulation methods. Both comparisons are wrong because GPS observations are pseudoranges containing clock errors. The geometric interpretations of GPS relative positioning and trilateration method are presented. Receiver clock parameter is also analyzed from a geometric point of view. The generalization of positioning solutions is made without and with observations redundancy. The geometry of the propagation of systematic errors into positioning solutions is also shown, especially the tropospheric (and the ionospheric) delay.
  • Publication
    Accès libre
    Floating lines and cones for use as a GPS mission planning aid.
    (American Society of Photogrammetry, 1996-03-01) Boulianne, Michel; Santerre, Rock; Nolette, Clément; Gagnon, Paul-André
    This paper presents a new method for generating obstruction diagrams as a function of site obstacles for GPS observations. The proposed method takes advantage of the human ability for stereoscopic vision. Instead of going on the site and measuring the azimuth and elevation angle of every obstacle in the vicinity of a prospective GPS point, the photogrammetric approach proposes using a visibility cone injected into a stereoscopic model. In this way, the time consuming and costly phase of site reconnaissance is eliminated. In the presence of obstructions, the cone rays that are lower than the obstacles are raised like floating lines. Afterwards, by recording the azimuth and elevation angles of these rays, obstruction contours can be generated. With this diagram, superimposed on the satellite track plot, the mission planner can evaluate the best GPS observation window based, for example, on Geometric Dilution of Precision (GDOP). A practical test shows the applicability and feasibility of the method.
  • Publication
    Accès libre
    GPS attitude for a berthing guidance system.
    (Canadian Aeronautics and Space Institute, 1999-09-01) Santerre, Rock; Ueno, Mami
    This study was conducted on a ship's automatic berthing system where precise and real-time estimation of the state vector is required, e.g., heading ±0.05° for berthing of a 300 m ship. Rapid and reliable phase ambiguity resolution provides the ultimate accuracy for GPS attitude determination. The onboard GPS-based attitude system, consisting of an optimal 4-antenna configuration, has the capability of single-epoch ambiguity resolution and least-squares algorithms for attitude determination. The GPS results were compared with external sensors on board a hydrographic sounding ship. The RMS values of the difference of attitude angles between GPS and TSS/gyrocompass were: ±0.60° for heading, ±0.44° for roll and ±0.34° for pitch with GPS antenna separation of about 1.4 m. The new algorithms allow fast ambiguity resolution and would be suitable for real-time applications. As precision of attitude determination can be improved by extending baselines, a 5 m baseline configuration could satisfy the sensor requirements for berthing of a 300-m ship. The GPS-based attitude system has utilization potential for a berthing guidance system.
  • Publication
    Direct determination of angular velocity using GPS
    (Cambridge University Press, 2000-05-01) Santerre, Rock; Ueno, Mami; Kleusberg, Alfred
    Controlling a ship in a berthing operation is carried out mainly by the change of state, such as velocity and yaw rate (turn rate), although the value of the change of state is very small at berthing. Very high precision is, therefore, required to determine the velocity and angular velocity. A sensor that has an accuracy of ±0.02°/s (1 s) is sought for determination of turn rate in a berthing system. Three-dimensional angular velocity can directly be determined, with 2 independent baselines of 3 GPS antennas, using instantaneous Doppler measurements or phase rate (temporal difference of phase) observations. This paper discusses the mathematical model for direct determination of angular velocity using GPS, and the comparison of the results of the angular velocity determination using the Doppler and phase rate. The precision of angular velocity determination is estimated using temporal difference of the attitude sensors (TSS and gyrocompass) on board a hydrographic sounding ship. The RMS values of the difference of yaw rate determination between the two systems were: ±0.16°/s using phase rate and ±0.31°/s using Doppler measurements with the separation of onboard antennas of ca. 1·34 m. 10 m baselines could satisfy the sensor requirements for angular velocity determination during berthing maneuvers.
  • Publication
    GPS interactive time series analysis software
    (John Wiley & Sons, 2012-10-12) Santerre, Rock; Goudarzi, Mohammad Ali; Cocard, Marc; Woldai, Tsehaie
    Time series analysis is an important part of geodetic and geodynamic studies, especially when continuous GPS observations are used to explore areas with a low rate of deformation. In this domain, having precise and robust tools for processing and analyzing position time series is a prerequisite. To meet this requirement, a new software package called GPS Interactive Time Series Analysis was developed using the MATLAB language. Along with calculating basic statistics and quality parameters such as mean and variance, the software is capable of importing and visualizing different time series formats, determining and removing jumps and outliers, interpolating data, and producing numerical and publication quality graphical outputs. Furthermore, bivariate statistical analysis (such as correlation coefficients, curvilinear and nonlinear regression), residual analysis, and spectral analysis (such as auto-spectrum, Lomb–Scargle spectrum, evolutionary power spectrum, and wavelet power spectrum) form the main analysis features of the software.
  • Publication
    La formation et la recherche en acquisition et traitement de données géomatiques au Département des sciences géomatiques de l’Université Laval
    (Association canadienne des sciences géomatiques, 2007-09-01) Boulianne, Michel; Santerre, Rock; Mostafavi, Mir Abolfazl; Daniel, Sylvie; Viau, Alain; Cocard, Marc
    De nombreux projets de recherche en acquisition et traitement de données géomatiques ont cours au Département des sciences géomatiques de l’Université Laval. Les projets se sont particulièrement diversifiés ces dernières décennies. Une description des principaux projets passés et actuels est présentée. Ceux-ci se rapportent principalement aux domaines du positionnement par satellites, de la photogrammétrie, de l’imagerie numérique et de la télédétection. Ces projets couvrent autant les aspects fondamentaux en géomatique que des applications concrètes et novatrices dans divers domaines (agriculture, architecture, archéologie, auscultation topographique, performances sportives, etc.). Finalement, quelques projets intégrateurs qui allient plusieurs disciplines de la géomatique sont présentés et démontrent la synergie de ces disciplines d’acquisition et de traitement de données géomatiques.
  • Publication
    Où va l’enseignement de la géomatique? Vers des infrastructures géospatiales d’enseignement de la géomatique
    (Canadian Institute of Geomatics, 2007-09-01) Santerre, Rock; Chrisman, Nicholas; Roche, Stéphane; Daniel, Sylvie; Bédard, Yvan; Roy, Francis
    Sur la base d’une expérience de 100 ans de formation en géomatique à l’Université Laval, certaines tendances en matière d’enseignement peuvent être extraites. Cet article aborde le contenu des cours universitaires en géomatique et les méthodes d’enseignement de cette discipline. Le contenu des cours doit s’ajuster à la convergence des technologies considérant, entre autres exemples, que les moyens de localisation sont intégrés dans des appareils ubiquistes de plus en plus miniaturisés. Un enjeu important dans la conception de l’enseignement est la « demi-vie » du matériel pédagogique enseigné. D’égale importance est le contexte sociétal de l’utilisation des technologies géomatiques. En même temps, les méthodes d’enseignement doivent évoluer à cause des pressions exercées par les changements technologiques. Une conclusion importante est que l’enseignement de la géomatique requiert des investissements substantiels dans les infrastructures géospatiales
  • Publication
    Improvement of GPS phase ambiguity resolution using prior height information as a quasi-observation.
    (Canadian Institute of Geomatics, 2002-09-01) Santerre, Rock; Zhu, Jianjun
    La résolution des ambiguïtés sur les phases du GPS sur L1 est toujours difficile pour l'arpentage cinématique, particulièrement lorsque la ligne de base est longue. Une approche intéressante consiste à combiner les observations GPS à l'information d'autres systèmes d'arpentage ou d'autres sources pour améliorer la résolution des ambiguïtés. En levés bathymétriques, l'information antérieure sur la hauteur peut être obtenue à partir de marégraphes. La présente recherche est entreprise pour étudier comment utiliser l'information antérieure sur la hauteur et comment obtenir une solution stable. Il s'agit d'une méthode qui utilise la hauteur antérieure comme une quasi-observation. Celle-ci est ensuite utilisée dans la compensation avec les observations GPS. Dans cette contribution, un algorithme est d'abord développé pour le calcul de compensation avec la quasi-observation. La capacité de la quasi-observation d'améliorer la technique de recherche est ensuite étudiée en détail. Les résultats montrent que non seulement la quasi-observation peut renforcer les tests pour éliminer les solutions incorrectes, mais elle peut aussi changer avantageusement la structure de l'espace de recherche des ambiguïtés. La stabilité de la méthode est également examinée. Enfin, des tests sur place sont entrepris pour démontrer que l'approche proposée est efficace. Les résultats des tests montrent que pour les levés bathymétriques dans le fleuve Saint-Laurent, si la technique d'interpolation de la marée est utilisée et si l'assise, le tangage et le tirant d'eau du bateau sont considérés, une précision de la hauteur antérieure () de 10 ou 20 centimètres peut être sélectionnée.