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Mapping the wavelength position of mineral features in hyperspectral thermal infrared data / Christoph Hecker in International journal of applied Earth observation and geoinformation, vol 79 (July 2019)  

Public [article]  inInternational journal of applied Earth observation and geoinformation > vol 79 (July 2019) . - pp 133-140 Titre : Mapping the wavelength position of mineral features in hyperspectral thermal infrared data Type de document : Article/Communication Auteurs : Christoph Hecker, Auteur ; Frank J.A. Van Ruitenbeek, Auteur ; Wim H. Bakker, Auteur ; Babatunde J. Fagbohun, Auteur ; et al., Auteur Année de publication : 2019 Article en page(s) : pp 133-140 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] carte géologique [Termes IGN] feldspath [Termes IGN] filtrage du bruit [Termes IGN] image aérienne [Termes IGN] image hyperspectrale [Termes IGN] image thermique [Termes IGN] longueur d'onde [Termes IGN] Nevada (Etats-Unis) [Termes IGN] prospection minérale [Termes IGN] quartz Résumé : (auteur) The Wavelength Mapper is an algorithm that searches for the deepest absorption feature in each pixel of a hyperspectral image. On a per pixel basis, it extracts the wavelength position, which serves as a proxy of the mineralogy and the feature depth as a proxy for the relative abundance. This algorithm has been used with near and shortwave infrared data, but has not yet been tested on hyperspectral thermal infrared images. It is unclear what results are expected when the Wavelength Mapper algorithm is applied to hyperspectral thermal infrared data since reststrahlen features characteristically overlap in emissivity spectra. In this paper, the Wavelength Mapper is tested on a multi-flightline airborne hyperspectral TIR dataset acquired over the Yerington Batholith, Nevada. Observations were made in the 8.05–11.65 μm wavelength range to include thermal spectral features of major rock-forming minerals, and a new color ramp is created to separate quartz-rich rocks from plagioclase-rich rocks. Our results indicate that the Wavelength Mapper creates coherent spatial patterns across flightlines. The results displayed represent different types of igneous and sedimentary rocks, as well as the products of hydrothermal alteration via different colors, mainly based on the relative abundance of quartz, feldspar and garnet, as well as mica and epidote. Comparison with published maps indicate that the Wavelength Mapper represents for each pixel a parameter value that can be linked to the spectrally dominate rock-forming mineral of that area, as mapped with traditional fieldwork methods. In conclusion, the Wavelength Mapper can be applied to airborne hyperspectral TIR data to achieve a simple, repeatable, per-pixel overview map of the dominating rock-forming mineral occurrences. Numéro de notice : A2019-467 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.jag.2019.02.013 Date de publication en ligne : 20/03/2019 En ligne : https://doi.org/10.1016/j.jag.2019.02.013 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93603 [article]

Hyperspectral edge filtering for measuring homogeneity of surface cover types / Wim H. Bakker in ISPRS Journal of photogrammetry and remote sensing, vol 56 n° 4 (July - August 2002)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 56 n° 4 (July - August 2002) . - pp 246 - 256 Titre : Hyperspectral edge filtering for measuring homogeneity of surface cover types Type de document : Article/Communication Auteurs : Wim H. Bakker, Auteur ; K.S. Schmidt, Auteur Année de publication : 2002 Article en page(s) : pp 246 - 256 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes IGN] distance euclidienne [Termes IGN] eau de mer [Termes IGN] filtrage numérique d'image [Termes IGN] image HYMAP [Termes IGN] image hyperspectrale [Termes IGN] marais Résumé : (Auteur) Edge operators are widely used on grey-level images as a first step in image segmentation or image interpretation. Methods that are currently used for edge filtering are complex and only valid under certain conditions, or useful for threeband colour images only. The problem remains on how to apply edge filtering on multispectral or even hyperspectral images. This paper presents a method that can be used for multispectral and hyperspectral edge filtering. The method uses filtering techniques in combination with three distance measures, namely the Euclidean distance, the spectrum intensity difference, or the spectral angle. The same hyperspectral edge filters serve as homogeneity measures. By simply 'plugging in' another distance measure in the same filter, a separation between intensity and spectral content is achieved, which makes the hyperspectral edge filters the natural extension of colour edge filters. The hyperspectral edge filters use information from all spectral bands to arrive at a (dis)similarity map in one step. The edge filters were tested on HyMap hyperspectral imagery of the island of Schiermormikoog. The test area includes agriculture and a saltmarsh. Experimental results are presented. The spectral angle (dis)similarity of neighbouring pixels can be directly compared with spectral angles already obtained by using the Spectral Angle Mapper for classification. We show that these hyperspectral edge filters assist image interpretation, even in heterogeneous ecosystems such as saltmarshes. Copyright ISPRS Numéro de notice : A2002-167 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/S0924-2716(02)00060-6 En ligne : https://doi.org/10.1016/S0924-2716(02)00060-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22082 [article]

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