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Pushing the sensitivity limits of RTS-based continuous deformation monitoring of an alpine valley / Mariusz Frukacz in Applied geomatics, vol 9 n° 2 (June 2017)
[article]
Titre : Pushing the sensitivity limits of RTS-based continuous deformation monitoring of an alpine valley Type de document : Article/Communication Auteurs : Mariusz Frukacz, Auteur ; Robert Presl, Auteur ; Andreas Wieser, Auteur ; Daniele Favot, Auteur Année de publication : 2017 Article en page(s) : pp 81 - 92 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] déformation de la croute terrestre
[Termes IGN] glacier
[Termes IGN] orientation du capteur
[Termes IGN] réfraction atmosphérique
[Termes IGN] Suisse
[Termes IGN] surveillance géologique
[Termes IGN] tachéomètre électronique robotiséRésumé : (auteur) Monitoring applications may require operating robotic total stations (RTS) at the limit of their sensitivity with respect to target displacements. Thorough understanding and mitigation of systematic effects are required in order to reach or push this limit. We investigate some of these effects, in particular effects external to the total station, using data and experience gained from a continuously operating monitoring system installed at the terminus of the Great Aletsch Glacier in Switzerland. The system consists of two robotic total stations, about 60 prisms, four global navigation satellite system (GNSS) receivers, thermocouples, inclinometers, and meteo-sensors. The purpose of the monitoring is to study reversible deformations of the adjacent slopes, likely driven by snowmelt and mountain water level changes. The deformations reach the millimeter- to centimeter-level and shall be studied on time scales ranging from annual to sub-annual, and ideally even down to daily or sub-daily resolution. Our investigation focuses on four aspects: protective housing, pillar stability, refraction, and stability of orientation, all of which were found to affect the measurements on the milligon-level with lines-of-sight of up to 2 km. The results highlight signatures of apparent point displacements, and the discussion comprises approaches to bounding or mitigating these effects which may also be expected in similar monitoring situations at other locations. Numéro de notice : A2017-359 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s12518-017-0182-2 Date de publication en ligne : 21/01/2017 En ligne : http://doi.org/10.1007/s12518-017-0182-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85768
in Applied geomatics > vol 9 n° 2 (June 2017) . - pp 81 - 92[article]Evaluation of multisource data for glacier terrain mapping : a neural net approach / Aparna Shukla in Geocarto international, vol 32 n° 5 (May 2017)
[article]
Titre : Evaluation of multisource data for glacier terrain mapping : a neural net approach Type de document : Article/Communication Auteurs : Aparna Shukla, Auteur ; Bisma Yousuf, Auteur Année de publication : 2017 Article en page(s) : pp 569 - 587 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] bande infrarouge
[Termes IGN] carte topographique
[Termes IGN] classification par maximum de vraisemblance
[Termes IGN] classification par réseau neuronal
[Termes IGN] couche thématique
[Termes IGN] données auxiliaires
[Termes IGN] données multisources
[Termes IGN] glacier
[Termes IGN] image Landsat-TM
[Termes IGN] image multibandeRésumé : (Auteur) Spectrally similar nature of land covers in a glacierized terrain hampers their automated mapping from multispectral satellite data, which may be overcome by using multisource data. In the present study, an artificial neural network (ANN)-based information extraction approach was applied for mapping the Kolahoi glacier and adjoining areas, using Landsat TM (Thematic Mapper) data and several ancillary layers such as image transformations and topographic attributes. Results reveal that ANN (highest overall accuracy (OA): 83.74%) outperforms maximum likelihood classifier (highest OA: 66.90%) and the incorporation of ancillary data into the classification process significantly enhances the mapping accuracy (>9%), particularly the addition of Near Infrared Red/Short Wave Infrared (NIR/SWIR) data to the spectral data. A nine-band combination dataset (spectral data, slope, Red/NIR and decorrelation stretch) was found to be the best multisource dataset. Results of the Z-tests (at 95% confidence level) also corroborate and statistically validate the above findings. Numéro de notice : A2017-274 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/10106049.2016.1161078 Date de publication en ligne : 28/03/2016 En ligne : http://dx.doi.org/10.1080/10106049.2016.1161078 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85303
in Geocarto international > vol 32 n° 5 (May 2017) . - pp 569 - 587[article]
Titre : Monitoring rock glaciers by combining photogrammetric and GNSS-based methods Type de document : Thèse/HDR Auteurs : Fabian Neyer, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2017 Autre Editeur : Zurich : Eidgenossische Technische Hochschule ETH - Ecole Polytechnique Fédérale de Zurich EPFZ Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 99 Importance : 174 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-45-1 Note générale : bibliographie
thesis submitted to attain the degree of doctor of sciences of ETH ZurichLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques
[Termes IGN] Alpes centrales
[Termes IGN] champ de vitesse
[Termes IGN] collocation par moindres carrés
[Termes IGN] déformation de la croute terrestre
[Termes IGN] données localisées 3D
[Termes IGN] glacier
[Termes IGN] image terrestre
[Termes IGN] matrice de covariance
[Termes IGN] pergélisol
[Termes IGN] reconstruction 3D
[Termes IGN] rocher
[Termes IGN] série temporelle
[Termes IGN] SuisseIndex. décimale : 30.60 Géodésie spatiale Résumé : (auteur) Rock glaciers are creeping landforms of perennially frozen ground and belong to the permafrost creeping phenomena. They are mainly composed of rock debris that accumulate in areas of high natural erosion. Ice particles between the rocks cause the moving accumulation in steep terrain to dynamically flow downslope. In the Alpine region, these morphological landforms mainly occur at north-facing mountain slopes in high altitudes above the forest boundary and are known for their sensitivity to climate change.
For several decades, rock glaciers have been monitored for scientific aims, while advances in surveying technologies increased the interest in such studies since the 1990s. Modern technologies in remote sensing (e.g., airborne imagery or satellite-based measurement techniques) are often combined with measurements from field campaigns, i.e., measurements taken directly on a rock glacier (e.g., GNSS, laser-scanning, ground temperature measurements, etc). The high-level goal is to enhance the process understanding, especially with respect to the changing climate: various studies indicate an extended risk of slope failures in steep frozen bedrock due to the global temperature increase. Early recognition of increased activities help to inform local authorities in the endangered areas about the potential hazard before such an event.
The present work is part of the X-Sense project (Nano-Tera.ch), with an interdisciplinary team of scientists that build and operate new low-cost devices for data acquisition, develop new data processing pipelines and algorithms for evaluation, and also gain new insight of natural processes in these regions. Autonomous measurement systems, developed within other work packages in the X-Sense project, observe different permafrost creep areas with high resolution in space and time. Combined with multi-year observations, the derived surface motions are used to obtain an improved process understanding.
This work focuses on the photogrammetric image processing in order to retrieve precise surface displacement estimates. More precisely, image sequences, acquired with two permanently installed commercial digital single-reflex cameras, are used to measure topographic changes in the observed permafrost area. By the combination with high resolution GNSS positioning results, the goal is to obtain precise time series of moving rock boulders at different positions within the field of view. Challenges arising from the combination of different data sets, the development of an automatic processing pipeline, and an improvement of the processing strategy in general, are the main tasks of this thesis.
The study site is the bordering area above the Grabengufer rock glacier (Mattervalley VS, Switzerland), known as the Grabengufer rock slide. Local topographic conditions allowed only a partially good installation geometry for the photogrammetric reconstruction. With respect to a 3D reconstruction without the use of GNSS coordinates, an accuracy increase of about one order of magnitude could be achieved in case these high-precision solutions were integrated. More specifically, respective standard deviations for the East, North, and Height components of 6, 5, and 2 cm were achieved. The stated accuracy, maintained throughout the measurement period of nearly four years (summer months), was obtained in an area of approximately 80m×80 m, with a mean distance of 80 m from the two cameras.
Position time series of moving rock boulders were filtered using the principles of collocation. Analyzing the correlation characteristics of the stochastic signal, an optimal correlation length was computed and used to extract relevant signals from the noise contaminated time series. Velocity was directly estimated as a derived quantity in the collocation process. Furthermore, the techniques of the adaptive collocation approach is presented. This iterative method uses the principles of a dynamically adjusting anisotropic covariance metric. In an example of 2-dimensional velocity fields it is shown that regional compression and extension areas can be extracted.
Results indicate that the observed permafrost area has experienced a mean annual acceleration of about 0.1m/Year between the years 2013 and 2015. During the late summer months of 2015, a prominent temporal acceleration was observed. The mean displacement rate was found to be 0.67m/year, whereas the 3-dimensional displacement is dominated by a translation following the gliding surface. An area in the front of the observed field of view was found to have higher displacement rates, especially during the late summer months, thus it detaches from the otherwise relatively homogeneous flow field.
The methods and principles presented in this work show the potential of monitoring permafrost surface displacements using permanently installed optical cameras in combination with positioning results from permanently mounted GNSS stations. These principles can easily be transfered to other monitoring applications and thus contribute to a better understanding of such processes.Note de contenu : 1 Introduction
2 Study Site
3 Image-Based Displacement Estimation
4 Object Point Reconstruction
5 Collocation for Time Series Analysis
6 Results
7 Conclusions
8 OutlookNuméro de notice : 17458 Affiliation des auteurs : non IGN Autre URL associée : https://doi.org/10.3929/ethz-a-010865360 Thématique : IMAGERIE Nature : Thèse étrangère Note de thèse : thèse : Sciences : ETHZ : 2016 DOI : 10.3929/ethz-a-010865360 En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-99.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89683 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 17458-01 33.60 Livre Centre de documentation Photogrammétrie - Lasergrammétrie Disponible Remote sensing of alpine glaciers in visible and infrared wavelengths: a survey of advances and prospects / Anshuman Bhardwaj in Geocarto international, vol 31 n° 5 - 6 (May - June 2016)
[article]
Titre : Remote sensing of alpine glaciers in visible and infrared wavelengths: a survey of advances and prospects Type de document : Article/Communication Auteurs : Anshuman Bhardwaj, Auteur ; P.K. Joshi, Auteur ; Lydia Sam, Auteur ; Snehmani, Auteur Année de publication : 2016 Article en page(s) : pp 557 - 574 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] bande infrarouge
[Termes IGN] bande visible
[Termes IGN] glacier
[Termes IGN] image optique
[Termes IGN] image thermique
[Termes IGN] mouvement de terrainRésumé : (Auteur) Remote sensing is an efficient tool for temporal monitoring of inaccessible alpine glacial terrain. This study discusses the methods of remote sensing in visible and infrared (IR) wavelengths, which are helpful in providing important information about alpine glaciers. The scope of this study covers recent advances and prospects in optical and thermal remote sensing of glacier facies, glacier velocity, mass balance, glacial hazards and automated mapping techniques. The technology is ever evolving with the advent of new remote sensors capturing data in visible/IR wavelengths and better digital computing technology. An extensive list of significant studies further helps the reader to explore a particular topic of interest. We survey recent advances in this field and additionally highlight the emerging prospects. Numéro de notice : A2016-170 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/10106049.2015.1059903 Date de publication en ligne : 29/06/2015 En ligne : http://www.tandfonline.com/doi/full/10.1080/10106049.2015.1059903 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80510
in Geocarto international > vol 31 n° 5 - 6 (May - June 2016) . - pp 557 - 574[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 059-2016031 RAB Revue Centre de documentation En réserve L003 Disponible A new high-precision and low-power GNSS receiver for long-term installations in remote areas / David H. Jones in Geoscientific instrumentation methods and data systems, vol 5 n° 1 (January - June 2016)
[article]
Titre : A new high-precision and low-power GNSS receiver for long-term installations in remote areas Type de document : Article/Communication Auteurs : David H. Jones, Auteur ; Carl Robinson, Auteur ; G. Hilmar Gudmundsson, Auteur Année de publication : 2016 Article en page(s) : pp 65 - 73 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s)
[Termes IGN] glacier
[Termes IGN] méthode robuste
[Termes IGN] récepteur GNSSRésumé : (auteur) We have developed a new high-precision GNSS receiver specifically designed for long-term unattended deployments in remote areas. The receiver reports its status, and can be reprogrammed remotely, through an integrated satellite data link. It uses less power than commercially available alternatives while being equally, if not more, accurate. Data are saved locally on dual SD card slots for increased reliability. Deployments of a number of those receivers in several different locations on the Antarctic ice sheet have shown them to be robust and able to operate flawlessly at low temperatures down to −40 °C. Numéro de notice : A2016--052 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.5194/gi-5-65-2016 En ligne : http://dx.doi.org/10.5194/gi-5-65-2016 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80482
in Geoscientific instrumentation methods and data systems > vol 5 n° 1 (January - June 2016) . - pp 65 - 73[article]Documents numériques
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