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Accurate georeferencing of TLS point clouds with short GNSS observation durations even under challenging measurement conditions / Florian Zimmermann in Journal of applied geodesy, vol 12 n° 4 (October 2018)  

Public [article]  inJournal of applied geodesy > vol 12 n° 4 (October 2018) . - pp. 289 - 302 Titre : Accurate georeferencing of TLS point clouds with short GNSS observation durations even under challenging measurement conditions Type de document : Article/Communication Auteurs : Florian Zimmermann, Auteur ; Christoph Holst, Auteur ; Lasse Klingbeil, Auteur ; Heiner Kuhlmann, Auteur Année de publication : 2018 Article en page(s) : pp. 289 - 302 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] altitude [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] géoréférencement [Termes IGN] paramètre de temps [Termes IGN] point d'appui [Termes IGN] positionnement par GNSS [Termes IGN] précision des mesures [Termes IGN] semis de points Résumé : (auteur) The accuracy of georeferenced TLS point clouds is directly influenced by site-dependent GNSS effects, deteriorating the accuracy of the ground control point coordinate estimation. Especially under challenging GNSS conditions, this is a crucial problem. One common approach is to minimize these effects by longer observation durations, which in turn increases the effort in time and cost. In this paper, an algorithm is proposed that provides accurate georeferencing results, even under challenging measurement conditions and short observation durations. It iteratively improves the georeferencing accuracy by determining and applying obstruction adaptive elevation masks to the GNSS observations. The algorithm is tested and assessed using the data of a field test. It is demonstrated that after only 5 minutes observation duration, the ground control point coordinates can be estimated with an accuracy of 1 to 2 cm, independent from the GNSS measurement conditions. Initial states of the elevation masks are determined from a point cloud that is georeferenced using coordinates from a single point positioning solution, enhanced by a RAIM-FDE approach. Afterwards, the coordinates are estimated in a weighted least-squares baseline solution and both, the elevation masks and the coordinate estimation, are iteratively improved. Besides the significant reduction of measurement time, the proposed algorithm allows for increasing the amount of ground control points and can be applied to other direct or indirect GNSS-based georeferencing approaches. Numéro de notice : A2018-433 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1515/jag-2018-0013 Date de publication en ligne : 29/08/2018 En ligne : https://doi.org/10.1515/jag-2018-0013 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91000 [article]

Rigorous strip adjustment of UAV-based laserscanning data including time-dependent correction of trajectory errors / Philipp Glira 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 945 - 954 Titre : Rigorous strip adjustment of UAV-based laserscanning data including time-dependent correction of trajectory errors Type de document : Article/Communication Auteurs : Philipp Glira, Auteur ; Norbert Pfeifer, Auteur ; Gottfried Mandlburger, Auteur Année de publication : 2016 Article en page(s) : pp 945 - 954 Note générale : biblographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] compensation [Termes IGN] drone [Termes IGN] erreur systématique [Termes IGN] espace-temps [Termes IGN] étalonnage de capteur (imagerie) [Termes IGN] orientation du capteur [Termes IGN] paramètre de temps [Termes IGN] semis de points Résumé : (auteur) A new generation of laser scanners mounted on Unmanned Aerial Vehicles (UAVs) have the potential to provide high-quality point clouds of comparatively small areas (a few hectares). The high maneuverability of the UAVs, a typically large field of view of the laser scanners, and a comparatively small measurement range lead to point clouds with very high point density, less occlusions, and low measurement noise. However, due to the limited payload of UAVs, lightweight navigation sensors with a moderate level of accuracy are used to estimate the platform's trajectory. As a consequence, the georeferencing quality of the point clouds is usually sub-optimal; for this, strip adjustment can be performed. The main goal of strip adjustment is to simultaneously optimize the relative and absolute orientation of the strip-wise collected point clouds. This is done by fully re-calibrating the laser scanning system and by correcting systematic measurement errors of the trajectory. In this paper, we extend our previous work on the topic of strip adjustment by the estimation of time-dependent trajectory errors. The errors are thereby modelled by natural cubic splines with constant segment length in time domain. First results confirm the suitability of this flexible correction model by reducing the relative and absolute strip discrepancies to 1.38 cm and 1.65 cm, respectively. Numéro de notice : A2016-983 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.82.12.945 En ligne : https://doi.org/10.14358/PERS.82.12.945 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83699 [article]

Asynchronous RTK precise DGNSS positioning method for deriving a low-latency high-rate output / Zhang Liang in Journal of geodesy, vol 89 n° 7 (July 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 7 (July 2015) . - pp 641 - 653 Titre : Asynchronous RTK precise DGNSS positioning method for deriving a low-latency high-rate output Type de document : Article/Communication Auteurs : Zhang Liang, Auteur ; Lv Hanfeng, Auteur ; Wang Dingjie, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 641 - 653 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] paramètre de temps [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement différentiel [Termes IGN] positionnement par GNSS [Termes IGN] station GNSS [Termes IGN] synchronisation [Termes IGN] transmission de données Résumé : (auteur) Low-latency high-rate (>1 Hz) precise real-time kinematic (RTK) can be applied in high-speed scenarios such as aircraft automatic landing, precise agriculture and intelligent vehicle. The classic synchronous RTK (SRTK) precise differential GNSS (DGNSS) positioning technology, however, is not able to obtain a low-latency high-rate output for the rover receiver because of long data link transmission time delays (DLTTD) from the reference receiver. To overcome the long DLTTD, this paper proposes an asynchronous real-time kinematic (ARTK) method using asynchronous observations from two receivers. The asynchronous observation model (AOM) is developed based on undifferenced carrier phase observation equations of the two receivers at different epochs with short baseline. The ephemeris error and atmosphere delay are the possible main error sources on positioning accuracy in this model, and they are analyzed theoretically. In a short DLTTD and during a period of quiet ionosphere activity, the main error sources decreasing positioning accuracy are satellite orbital errors: the “inverted ephemeris error” and the integration of satellite velocity error which increase linearly along with DLTTD. The cycle slip of asynchronous double-differencing carrier phase is detected by TurboEdit method and repaired by the additional ambiguity parameter method. The AOM can deal with synchronous observation model (SOM) and achieve precise positioning solution with synchronous observations as well, since the SOM is only a specific case of AOM. The proposed method not only can reduce the cost of data collection and transmission, but can also support the mobile phone network data link transfer mode for the data of the reference receiver. This method can avoid data synchronizing process besides ambiguity initialization step, which is very convenient for real-time navigation of vehicles. The static and kinematic experiment results show that this method achieves 20 Hz or even higher rate output in real time. The ARTK positioning accuracy is better and more robust than the combination of phase difference over time (PDOT) and SRTK method at a high rate. The ARTK positioning accuracy is equivalent to SRTK solution when the DLTTD is 0.5 s, and centimeter level accuracy can be achieved even when DLTTD is 15 s. Numéro de notice : A2015-353 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0803-7 Date de publication en ligne : 15/03/2015 En ligne : http://dx.doi.org/10.1007/s00190-015-0803-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76776 [article]

The impact of common versus separate estimation of orbit parameters on GRACE gravity field solutions / U. Meyer in Journal of geodesy, vol 89 n° 7 (July 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 7 (July 2015) . - pp 685 - 696 Titre : The impact of common versus separate estimation of orbit parameters on GRACE gravity field solutions Type de document : Article/Communication Auteurs : U. Meyer, Auteur ; Adrian Jäggi, Auteur ; Gerhard Beutler, Auteur ; Heike Bock, Auteur Année de publication : 2015 Article en page(s) : pp 685 - 696 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] données GRACE [Termes IGN] élément orbital [Termes IGN] orbitographie [Termes IGN] paramètre de temps [Termes IGN] propagation du signal [Termes IGN] traitement du signal Résumé : (auteur) Gravity field parameters are usually determined from observations of the GRACE satellite mission together with arc-specific parameters in a generalized orbit determination process. When separating the estimation of gravity field parameters from the determination of the satellites’ orbits, correlations between orbit parameters and gravity field coefficients are ignored and the latter parameters are biased towards the a priori force model. We are thus confronted with a kind of hidden regularization. To decipher the underlying mechanisms, the Celestial Mechanics Approach is complemented by tools to modify the impact of the pseudo-stochastic arc-specific parameters on the normal equations level and to efficiently generate ensembles of solutions. By introducing a time variable a priori model and solving for hourly pseudo-stochastic accelerations, a significant reduction of noisy striping in the monthly solutions can be achieved. Setting up more frequent pseudo-stochastic parameters results in a further reduction of the noise, but also in a notable damping of the observed geophysical signals. To quantify the effect of the a priori model on the monthly solutions, the process of fixing the orbit parameters is replaced by an equivalent introduction of special pseudo-observations, i.e., by explicit regularization. The contribution of the thereby introduced a priori information is determined by a contribution analysis. The presented mechanism is valid universally. It may be used to separate any subset of parameters by pseudo-observations of a special design and to quantify the damage imposed on the solution. Numéro de notice : A2015-354 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0807-3 Date de publication en ligne : 29/03/2015 En ligne : https://doi.org/10.1007/s00190-015-0807-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76777 [article]

Estimated SLR station position and network frame sensitivity to time-varying gravity / Nikita P. Zelensky in Journal of geodesy, vol 88 n° 6 (June 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 6 (June 2014) . - pp 517 - 537 Titre : Estimated SLR station position and network frame sensitivity to time-varying gravity Type de document : Article/Communication Auteurs : Nikita P. Zelensky, Auteur ; Franck G. Lemoine, Auteur ; Douglas S. Chinn, Auteur ; Stavros A. Melachroinos, Auteur ; et al., Auteur Année de publication : 2014 Article en page(s) : pp 517 - 537 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] données Lageos [Termes IGN] gravité normale [Termes IGN] orbitographie [Termes IGN] paramètre de temps [Termes IGN] station TLS (télémétrie) Résumé : (Auteur) This paper evaluates the sensitivity of ITRF2008-based satellite laser ranging (SLR) station positions estimated weekly using LAGEOS-1/2 data from 1993 to 2012 to non-tidal time-varying gravity (TVG). Two primary methods for modeling TVG from degree-2 are employed. The operational approach applies an annual GRACE-derived field, and IERS recommended linear rates for five coefficients. The experimental approach uses low-order/degree 44 coefficients estimated weekly from SLR and DORIS processing of up to 11 satellites (tvg4x4). This study shows that the LAGEOS-1/2 orbits and the weekly station solutions are sensitive to more detailed modeling of TVG than prescribed in the current IERS standards. Over 1993–2012 tvg4x4 improves SLR residuals by 18 % and shows 10 % RMS improvement in station stability. Tests suggest that the improved stability of the tvg4x4 POD solution frame may help clarify geophysical signals present in the estimated station position time series. The signals include linear and seasonal station motion, and motion of the TRF origin, particularly in Z. The effect on both POD and the station solutions becomes increasingly evident starting in 2006. Over 2008–2012, the tvg4x4 series improves SLR residuals by 29 %. Use of the GRGS RL02 5050 series shows similar improvement in POD. Using tvg4x4, secular changes in the TRF origin Z component double over the last decade and although not conclusive, it is consistent with increased geocenter rate expected due to continental ice melt. The test results indicate that accurate modeling of TVG is necessary for improvement of station position estimation using SLR data Numéro de notice : A2014-286 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0701-4 Date de publication en ligne : 06/03/2014 En ligne : https://doi.org/10.1007/s00190-014-0701-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33189 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2014061	SL	Revue	Centre de documentation	Revues en salle	Disponible

Real-time clock jump compensation for precise point positioning / Fei Guo in GPS solutions, vol 18 n° 1 (january 2014)  

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Intégration de plans anciens dans un SIG : analyse spatio-temporelle du paysage clunisois / Z. Petty (01/09/2011)

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An ensemble approach to space-time interpolation / E. Wentz in International journal of geographical information science IJGIS, vol 24 n° 9 (september 2010)  

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New, improved GPS: the legacy accuracy improvement initiative / T. Creel in GPS world, vol 17 n° 3 (March 2006)

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