Centre de documentation
scientifique

Impact of different sampling rates on precise point positioning performance using online processing service / Serdar Erol in Geo-spatial Information Science, vol 24 n° 2 (June 2021)  

Public [article]  inGeo-spatial Information Science > vol 24 n° 2 (June 2021) . - pp 302 - 312 Titre : Impact of different sampling rates on precise point positioning performance using online processing service Type de document : Article/Communication Auteurs : Serdar Erol, Auteur ; Reha Metin Alkan, Auteur ; I. Murat Ozulu, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : pp 302 - 312 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] données GNSS [Termes IGN] format RINEX [Termes IGN] instrumentation Trimble [Termes IGN] intervalle de confiance [Termes IGN] phase GNSS [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] précision du positionnement [Termes IGN] rapport signal sur bruit [Termes IGN] réalité de terrain [Termes IGN] retard troposphérique zénithal [Termes IGN] taux d'échantillonnage [Termes IGN] trajet multiple [Termes IGN] Turquie Résumé : (auteur) In this study, the effect of different sampling rates (i.e. observation recording interval) on the Precise Point Positioning (PPP) solutions in terms of accuracy was investigated. For this purpose, a field test was carried out in Çorum province, Turkey, on 11 September 2019. Within this context, a Geodetic Point (GP) was established and precisely coordinated. A static GNSS measurement was occupied on the GP for about 4-hour time at 0.10 second (s)/10 Hz measurement intervals with the Trimble R10 geodetic grade GNSS receiver. The original observation file was converted to RINEX format and then decimated into the different data sampling rates as 0.2 s, 0.5 s, 1 s, 5 s, 10 s, 30 s, 60 s, and 120 s. All these RINEX observation files were submitted to the Canadian Spatial Reference System-Precise Point Positioning (CSRS-PPP) online processing service the day after the data collection date by choosing both static and kinematic processing options. In this way, PPP-derived static coordinates, and the kinematic coordinates of each measurement epoch were calculated. The PPP-derived coordinates obtained from each decimated sampling intervals were compared to known coordinates of the GP for northing, easting, 2D position, and height components. According to the static and kinematic processing results, high data sampling rates did not change the PPP solutions in terms of accuracy when compared to the results obtained using lower sampling rates. The results of this study imply that it was not necessary to collect GNSS data with high-rate intervals for many surveying projects requiring cm-level accuracy. Numéro de notice : A2021-558 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/10095020.2020.1842811 Date de publication en ligne : 25/11/2020 En ligne : https://doi.org/10.1080/10095020.2020.1842811 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98111 [article]

Uncertainty assessment in geodetic network adjustment by combining GUM and Monte-Carlo-simulations / Wolfgang Niemeier in Journal of applied geodesy, vol 11 n° 2 (June 2017)  

Public [article]  inJournal of applied geodesy > vol 11 n° 2 (June 2017) . - pp 67 - 76 Titre : Uncertainty assessment in geodetic network adjustment by combining GUM and Monte-Carlo-simulations Type de document : Article/Communication Auteurs : Wolfgang Niemeier, Auteur ; Dieter Tengen, Auteur Année de publication : 2017 Article en page(s) : pp 67 - 76 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] compensation de coordonnées [Termes IGN] données GNSS [Termes IGN] incertitude géométrique [Termes IGN] intervalle de confiance [Termes IGN] matrice de covariance [Termes IGN] méthode de Monte-Carlo [Termes IGN] Metsähovi [Termes IGN] point de liaison (géodésie) [Termes IGN] réseau géodésique Résumé : (Auteur) In this article, first ideas are presented to extend the classical concept of geodetic network adjustment by introducing a new method for uncertainty assessment as two-step analysis. In the first step the raw data and possible influencing factors are analyzed using uncertainty modeling according to GUM (Guidelines to the Expression of Uncertainty in Measurements). This approach is well established in metrology, but rarely adapted within Geodesy. The second step consists of Monte-Carlo-Simulations (MC-simulations) for the complete processing chain from raw input data and pre-processing to adjustment computations and quality assessment. To perform these simulations, possible realizations of raw data and the influencing factors are generated, using probability distributions for all variables and the established concept of pseudo-random number generators. Final result is a point cloud which represents the uncertainty of the estimated coordinates; a confidence region can be assigned to these point clouds, as well. This concept may replace the common concept of variance propagation and the quality assessment of adjustment parameters by using their covariance matrix. It allows a new way for uncertainty assessment in accordance with the GUM concept for uncertainty modelling and propagation. As practical example the local tie network in “Metsähovi Fundamental Station”, Finland is used, where classical geodetic observations are combined with GNSS data. Numéro de notice : A2017-283 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2016-0017 En ligne : https://doi.org/10.1515/jag-2016-0017 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85316 [article]

Modeling Mediterranean forest structure using airborne laser scanning data / Francesca Bottalico in International journal of applied Earth observation and geoinformation, vol 57 (May 2017)  

Public [article]  inInternational journal of applied Earth observation and geoinformation > vol 57 (May 2017) . - pp 145 - 153 Titre : Modeling Mediterranean forest structure using airborne laser scanning data Type de document : Article/Communication Auteurs : Francesca Bottalico, Auteur ; Gherardo Chirici, Auteur ; Raffaello Giannini, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 145 - 153 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] analyse comparative [Termes IGN] complexité [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] forêt méditerranéenne [Termes IGN] intervalle de confiance [Termes IGN] Italie [Termes IGN] structure d'un peuplement forestier Résumé : (auteur) The conservation of biological diversity is recognized as a fundamental component of sustainable development, and forests contribute greatly to its preservation. Structural complexity increases the potential biological diversity of a forest by creating multiple niches that can host a wide variety of species. To facilitate greater understanding of the contributions of forest structure to forest biological diversity, we modeled relationships between 14 forest structure variables and airborne laser scanning (ALS) data for two Italian study areas representing two common Mediterranean forests, conifer plantations and coppice oaks subjected to irregular intervals of unplanned and non-standard silvicultural interventions. The objectives were twofold: (i) to compare model prediction accuracies when using two types of ALS metrics, echo-based metrics and canopy height model (CHM)-based metrics, and (ii) to construct inferences in the form of confidence intervals for large area structural complexity parameters. Our results showed that the effects of the two study areas on accuracies were greater than the effects of the two types of ALS metrics. In particular, accuracies were less for the more complex study area in terms of species composition and forest structure. However, accuracies achieved using the echo-based metrics were only slightly greater than when using the CHM-based metrics, thus demonstrating that both options yield reliable and comparable results. Accuracies were greatest for dominant height (Hd) (R2 = 0.91; RMSE% = 8.2%) and mean height weighted by basal area (R2 = 0.83; RMSE% = 10.5%) when using the echo-based metrics, 99th percentile of the echo height distribution and interquantile distance. For the forested area, the generalized regression (GREG) estimate of mean Hd was similar to the simple random sampling (SRS) estimate, 15.5 m for GREG and 16.2 m SRS. Further, the GREG estimator with standard error of 0.10 m was considerable more precise than the SRS estimator with standard error of 0.69 m. Numéro de notice : A2017-369 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.jag.2016.12.013 En ligne : https://doi.org/10.1016/j.jag.2016.12.013 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85787 [article]