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Antenna phase center correction differences from robot and chamber calibrations: the case study LEIAR25 / Grzegorz Krzan in GPS solutions, vol 24 n° 2 (April 2020)  

Public [article]  inGPS solutions > vol 24 n° 2 (April 2020) Titre : Antenna phase center correction differences from robot and chamber calibrations: the case study LEIAR25 Type de document : Article/Communication Auteurs : Grzegorz Krzan, Auteur ; Karol Dawidowicz, Auteur ; Pawel Wielgosz, Auteur Année de publication : 2020 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] antenne GLONASS [Termes IGN] antenne GNSS [Termes IGN] antenne GPS [Termes IGN] centre de phase [Termes IGN] chambre anéchoïque [Termes IGN] correction du signal [Termes IGN] étalonnage d'instrument [Termes IGN] instrumentation Leica [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] robot [Termes IGN] série temporelle [Termes IGN] signal GNSS Résumé : (auteur) In recent years, the Global Navigation Satellite Systems (GNSS) have been intensively modernized, resulting in the introduction of new carrier frequencies for GPS and GLONASS and the development of new satellite systems such as Galileo and BeiDou (BDS). For this reason, the absolute field antenna calibrations performed so far for the two legacy carrier frequencies, the GPS and GLONASS, seem to be insufficient. Hence, all antennas will require a re-calibration of their phase center variations for the new signals to ensure the highest measurement accuracy. Currently, two absolute calibration methods are used to calibrate GNSS antennas: field calibration using a robot and calibration in an anechoic chamber. Unfortunately, differences in these methodologies also result in a disparity in the obtained antenna phase center corrections (PCC). Therefore, we analyze the differences between individual PCC obtained with these two methods, specifically for the Leica AR-25 antenna model (LEIAR25). In addition, the influence of PCC differences on the GNSS-derived position time series for 19 EUREF Permanent GNSS Network (EPN) stations was also assessed. The results show that the calibration method has a noticeable impact on PCC models. PCC differences determined for the ionosphere-free combination may reach up over 20 mm and can be transferred to the position domain. Further tests concerning the positioning accuracy showed that for horizontal coordinates differences between solutions were mostly below 1 mm, exceeding 2 mm only at two stations for the GLONASS solution. However, the height component differences exceeded 5 mm for four, six and six stations out of 19 for the GPS, GLONASS and Galileo solutions, respectively. These differences are strongly dependent on large L2 calibration differences. Numéro de notice : A2020-081 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-0957-5 Date de publication en ligne : 11/02/2020 En ligne : https://doi.org/10.1007/s10291-020-0957-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94650 [article]

Absolute field calibration for multi-GNSS receiver antennas at ETH Zurich / Daniel Willi in GPS solutions, vol 24 n° 1 (January 2020)  

Public [article]  inGPS solutions > vol 24 n° 1 (January 2020) Titre : Absolute field calibration for multi-GNSS receiver antennas at ETH Zurich Type de document : Article/Communication Auteurs : Daniel Willi, Auteur ; Simon Lutz, Auteur ; Elmar Brockmann, Auteur ; Markus Rothacher, Auteur Année de publication : 2020 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] antenne Galileo [Termes IGN] antenne GNSS [Termes IGN] antenne GPS [Termes IGN] centre de phase [Termes IGN] données Galileo [Termes IGN] données GPS [Termes IGN] données multicapteurs [Termes IGN] étalonnage au sol [Termes IGN] étalonnage d'instrument [Termes IGN] étalonnage des données [Termes IGN] international GPS service for geodynamics [Termes IGN] mesurage de phase [Termes IGN] récepteur GNSS [Termes IGN] robot [Termes IGN] signal GNSS [Termes IGN] Zurich (Suisse) Résumé : (Auteur) ETH Zurich developed an absolute GNSS antenna calibration system based on measurements taken in the field. An industrial robot is used to rotate and tilt the antenna to be calibrated. This procedure ensures good coverage of the antenna hemisphere and reduces systematic errors. The calibration system at ETH Zurich is validated by a direct comparison of the obtained calibrations with calibrations from the anechoic chamber method (University of Bonn) and from another absolute field calibration method (Geo++® GmbH). Calibrations by ETH Zurich agree on the sub-millimeter level with both reference calibrations. A second validation was conducted using real measurements on short baselines. Data were acquired on four stations in direct vicinity and processed using different phase center correction models. The experiment shows that individual corrections of ETH Zurich reduce the residuals in the coordinate domain when compared to type-mean calibrations of the International GNSS Service (IGS). However, residual biases between GPS and Galileo coordinates remain. These biases are efficiently reduced when using the new type-mean calibrations from the IGS that include calibration values for all GNSS, including Galileo. The ETH Zurich calibration system is proven to deliver meaningful calibrations that agree with other calibrations on the millimeter level in the azimuth and elevation domain. The field validation shows evidence that the consistency of the Galileo and GPS calibration should be further enhanced by performing a combined GPS and Galileo analysis, which is not yet implemented. Numéro de notice : A2020-020 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-019-0941-0 Date de publication en ligne : 19/12/2019 En ligne : https://doi.org/10.1007/s10291-019-0941-0 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94460 [article]

Impact of GPS processing on the estimation of snow water equivalent using refracted GPS signals / Ladina Steiner in IEEE Transactions on geoscience and remote sensing, vol 58 n° 1 (January 2020)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 58 n° 1 (January 2020) . - pp 123 - 135 Titre : Impact of GPS processing on the estimation of snow water equivalent using refracted GPS signals Type de document : Article/Communication Auteurs : Ladina Steiner, Auteur ; Michael Meindl, Auteur ; Christoph Marty, Auteur ; Alain Geiger, Auteur Année de publication : 2020 Article en page(s) : pp 123 - 135 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] Alpes [Termes IGN] altitude [Termes IGN] antenne GPS [Termes IGN] eau de fonte [Termes IGN] étalonnage des données [Termes IGN] manteau neigeux [Termes IGN] modèle hydrographique [Termes IGN] neige [Termes IGN] phase GPS [Termes IGN] pondération [Termes IGN] réfraction [Termes IGN] signal GPS [Termes IGN] Suisse Résumé : (auteur) Global navigation satellite system (GNSS) antennas buried underneath a snowpack have a high potential for in situ snow water equivalent (SWE) estimation. Automated and continuous SWE quantification independent of weather conditions could enhance snow hydrological monitoring and modeling. Accurate and reliable in situ data are needed for the calibration and validation of remote sensing data and snowpack modeling. A relative bias of less than 5% is achieved using sub-snow global positioning system (GPS) antennas (GPS refractometry) during a three full seasons time period in the Swiss Alps. A systematic overview regarding the temporal reliability of the sub-snow GPS derived results is, however, missing for this emerging technique. Moreover, GPS processing impacts the results significantly. Different GPS processing parameters are therefore selected and their influence on the SWE estimation is investigated. The impact of elevation-dependent weighting, the elevation cutoff angles, and the time intervals for SWE estimation are systematically assessed. The best results are achieved using all observations with an elevation-dependent weighting scheme. Moreover, the SWE estimation performance is equally accurate for hourly SWE estimation as for lower temporal resolutions up to daily estimates. The impact of snow on the coordinate solution is furthermore evaluated. While the east and north components are not systematically influenced by the overlying snowpack, the vertical component exhibits a significant variation and strongly depends on the SWE. The biased vertical component therefore provides an additional possibility to estimate SWE. Numéro de notice : A2020-074 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1109/TGRS.2019.2934016 Date de publication en ligne : 06/09/2019 En ligne : https://doi.org/10.1109/TGRS.2019.2934016 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94605 [article]

Impact of GPS antenna phase center models on zenith wet delay and tropospheric gradients / Yohannes Getachew Ejigu in GPS solutions, vol 23 n° 1 (January 2019)  

Public [article]  inGPS solutions > vol 23 n° 1 (January 2019) Titre : Impact of GPS antenna phase center models on zenith wet delay and tropospheric gradients Type de document : Article/Communication Auteurs : Yohannes Getachew Ejigu, Auteur ; Addisu Hunegnaw, Auteur ; Kibrom Ebuy Abraha, Auteur ; et al., Auteur Année de publication : 2019 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] antenne GPS [Termes IGN] centre de phase [Termes IGN] données GPS [Termes IGN] gradient de troposphère [Termes IGN] retard troposphérique zénithal [Termes IGN] teneur intégrée en vapeur d'eau [Vedettes matières IGN] Traitement de données GNSS Résumé : (Auteur) Today Global Navigation Satellite Systems (GNSS) tropospheric products, such as zenith total delays (ZTD) and zenith wet delays (ZWD), are widely used as complementary data sets in numerical weather prediction models. In particular, the wet delays are treated as unknown parameters in GNSS processing and are estimated with other parameters such as station coordinates. In this study, we investigate the effects of Phase Center Correction (PCC) models on ZWD, integrated water vapor (IWV) and horizontal gradients derived from Global Positioning System (GPS) observations. Two solutions were generated using the GAMIT software over the European Reference Frame (EUREF) Permanent GNSS Network (EPN). The first (reference) solution was derived by applying the International GNSS Service (IGS) type-mean PCC models, while for the second solution PCC models from individual calibrations were used. The solutions were generated identically, except for the PCC model differences. The tropospheric products from the two solutions were then compared, with the assumption that common signals would be differenced out. The comparison of the two solutions clearly shows a bias in all tropospheric products, which can be attributed to PCC model deficiencies. Overall, mean biases of 1.8, 0.3, 0.14 and 0.19 mm are evident in ZWD, IWV, North–South and East–West gradients, respectively. Moreover, the differences between the two solutions show seasonal variations. For all antenna types, the ZWD and IWV differences are dominated by white plus power-law noise, with the latter characterizing the low-frequency spectrum. On the other hand, the horizontal gradients exhibit a white plus first-order autoregressive noise characteristic with less than 1% white noise. The individual PCC model provides a better fit to an external independent model in terms of gradient estimates and also provides up to 3% more carrier phase integer ambiguity resolution. Numéro de notice : A2019-056 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-018-0796-9 Date de publication en ligne : 25/10/2018 En ligne : https://doi.org/10.1007/s10291-018-0796-9 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92085 [article]

Bundle adjustment of spherical images acquired with a portable panoramic image mapping system (PPIMS) / Yi-Hsing Tseng in Photogrammetric Engineering & Remote Sensing, PERS, vol 82 n° 12 (December 2016)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 82 n° 12 (December 2016) . - pp 935 - 943 Titre : Bundle adjustment of spherical images acquired with a portable panoramic image mapping system (PPIMS) Type de document : Article/Communication Auteurs : Yi-Hsing Tseng, Auteur ; Yung-Chuan Chen, Auteur ; Kuan-Ying Lin, Auteur Année de publication : 2016 Article en page(s) : pp 935 - 943 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] antenne GPS [Termes IGN] compensation par faisceaux [Termes IGN] image panoramique [Termes IGN] prise de vue terrestre [Termes IGN] spatiotriangulation [Termes IGN] système de numérisation mobile Résumé : (auteur) Thanks to the development of mobile mapping technologies, close-range photogrammetry (CRP) has advanced to be an efficient mapping method for a variety of applications. A compact CRP system equipped with multiple cameras and a GPS receiver is one of those advanced portable mapping systems. A portable panoramic image mapping system (PPIMS) was specially designed to capture panoramic images with eight cameras and to obtain the position of image station with a GPS receiver. A PPIMS can be considered as a panoramic CRP system. The coordinates of an object point can be determined by the intersection of panoramic image points. For the implementation, we propose a new concept of photogrammetry by using panoramic images. Eight images captured by PPIMS forms a spherical panorama image (SPI). Instead of using the original images, PPIMS SPIs are then used for photogrammetric triangulation and mapping. Under this circumstance, one SPI is formed for each station, and it is associated with only one set of exterior orientation (EO) parameters. Traditional collinearity equations are not applicable to SPI triangulation and mapping. Therefore, a novel bundle adjustment algorithm is proposed to solve EO of multi-station SPIs. Because PPIMS SPIs are not ideal SPIs, a correction scheme was also developed to correct the imperfect geometry of PPIMS SPI. Two test studies were performed for the data collected at a campus test field of National Cheng Kung University (NCKU) and at a historical site of Tainan. Both cases demonstrate the feasibility of SPI bundle adjustment and applying corrections for PPIMS SPIs necessary for effective for bundle adjustment. Furthermore, the experiment's results also confirm that SPIs can replace original images for PPIMS triangulation. Numéro de notice : A2016-982 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.82.12.935 En ligne : https://doi.org/10.14358/PERS.82.12.935 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83698 [article]

Inter-signal correction sensitivity analysis : aperture-dependent delays induced by antenna anisotropy in modernized GPS dual-frequency navigation / Gary Okerson in Inside GNSS, vol 11 n° 3 (May - June 2016)  

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Advanced modeling and algorithms for high-precision GNSS analysis / Kan Wang (2016)  

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Co-location of geodetic observation techniques in space / Benjamin Männel (2016)  

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Study of lever-arm effect using embedded photogrammetry and on-board GPS receiver on UAV for metrological mapping purpose and proposal of a free ground measurements calibration procedure / Mehdi Daakir (2016)  

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Analysis of orbital configurations for geocenter determination with GPS and low-Earth orbiters / Da Kuang in Journal of geodesy, vol 89 n° 5 (May 2015)  

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Galileo E1 and E5a Performance for multi-frequency, multi-constellation GBAS / Mihaela-Simona Circiu in GPS world, vol 26 n° 4 (April 2015)  

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GPS snow depth meter with geometry-free linear combinations of carrier phases / M. Ozeki in Journal of geodesy, vol 86 n° 3 (March 2012)  

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GPS-derived orbits for the GOCE satellite / Heike Bock in Journal of geodesy, vol 85 n° 11 (November /2011)  

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An inter-comparison of zenith tropospheric delays derived from DORIS and GPS data / Olivier Bock in Advances in space research, vol 46 n° 12 (15/12/2010)  

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The celestial mechanics approach : theoretical foundations / Gerhard Beutler in Journal of geodesy, vol 84 n° 10 (October 2010)  

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