TY - THES A1 - Bösche, Nina Kristine T1 - Detection of rare earth elements and rare earth oxides with hyperspectral spectroscopy T1 - Die Erkennung von Seltenerdelementen und Seltenerdoxiden mittels hyperspektraler Spektroskopie BT - near-field and spaceborne investigations in preparation of the EnMAP mission BT - Nahfeld und satellitengestützte Bildanalyse in Vorbereitung der EnMAP Mission N2 - The continuously increasing demand for rare earth elements in technical components of modern technologies, brings the detection of new deposits closer into the focus of global exploration. One promising method to globally map important deposits might be remote sensing, since it has been used for a wide range of mineral mapping in the past. This doctoral thesis investigates the capacity of hyperspectral remote sensing for the detection of rare earth element deposits. The definition and the realization of a fundamental database on the spectral characteristics of rare earth oxides, rare earth metals and rare earth element bearing materials formed the basis of this thesis. To investigate these characteristics in the field, hyperspectral images of four outcrops in Fen Complex, Norway, were collected in the near-field. A new methodology (named REEMAP) was developed to delineate rare earth element enriched zones. The main steps of REEMAP are: 1) multitemporal weighted averaging of multiple images covering the sample area; 2) sharpening the rare earth related signals using a Gaussian high pass deconvolution technique that is calibrated on the standard deviation of a Gaussian-bell shaped curve that represents by the full width of half maxima of the target absorption band; 3) mathematical modeling of the target absorption band and highlighting of rare earth elements. REEMAP was further adapted to different hyperspectral sensors (EO-1 Hyperion and EnMAP) and a new test site (Lofdal, Namibia). Additionally, the hyperspectral signatures of associated minerals were investigated to serve as proxy for the host rocks. Finally, the capacity and limitations of spectroscopic rare earth element detection approaches in general and of the REEMAP approach specifically were investigated and discussed. One result of this doctoral thesis is that eight rare earth oxides show robust absorption bands and, therefore, can be used for hyperspectral detection methods. Additionally, the spectral signatures of iron oxides, iron-bearing sulfates, calcite and kaolinite can be used to detect metasomatic alteration zones and highlight the ore zone. One of the key results of this doctoral work is the developed REEMAP approach, which can be applied from near-field to space. The REEMAP approach enables rare earth element mapping especially for noisy images. Limiting factors are a low signal to noise ratio, a reduced spectral resolution, overlaying materials, atmospheric absorption residuals and non-optimal illumination conditions. Another key result of this doctoral thesis is the finding that the future hyperspectral EnMAP satellite (with its currently published specifications, June 2015) will be theoretically capable to detect absorption bands of erbium, dysprosium, holmium, neodymium and europium, thulium and samarium. This thesis presents a new methodology REEMAP that enables a spatially wide and rapid hyperspectral detection of rare earth elements in order to meet the demand for fast, extensive and efficient rare earth exploration (from near-field to space). N2 - Die weltweit steigende Nachfrage nach seltenen Erden für technische Komponenten in modernen Technologien, rückt die Erkundung neuer Lagerstätten näher in den Fokus der globalen Exploration. Die Erkundung und Beschreibung neuer Lagerstätten mittels hyperspektraler Fernerkundung findet basierend auf Mineralkartierung bereits eine breite Anwendung. Diese Doktorarbeit befasst sich mit der Machbarkeit hyperspektraler Fernerkundung zur Detektion von Seltenerdelement-Vorkommen. Um dieser Fragestellung nachzukommen, wird eine grundlegende Datenbank der spektralen Eigenschaften von Seltenerdoxiden, Seltenerdmetallen und Seltenerdelement-haltigen Materialien hergestellt. Diese Eigenschaften wurden an vier Aufschlüssen des Fen Complexes in Norwegen hyperspektral analysiert. Auf dieser Grundlage wurde eine neue Methodik (REEMAP) entwickelt, die Seltenerdelement angereicherte Zonen im Aufschluss auffindet und kartiert. Die wichtigsten Schritte dieser Methode sind wie folgt: 1) multi-temporal gewichtete Mittelung mehrerer hyperspektraler Bilder des gleichen Ausschnittes; 2) Verstärkung des charakteristischen spektralen Merkmals unter Verwendung eines Hochpassfilterverfahrens, das auf der Standardabweichung einer Gaußkurve basiert die der gesuchten Absorptionsbande entspricht; 3) die mathematische Modellierung der gesuchten Absorptionsbande und thematische Klassifikation der Bildpixel. REEMAP wurde auf verschiedene Sensoren (EO-1 Hyperion und EnMAP) und ein neues Testgebiet (Lofdal, Namibia) re-kalibriert. Weiterhin wurde untersucht, inwiefern hyperspektrale Methoden zum Detektieren von Proxymineralen verwendet werden können. Die Limitationen der Seltenerd-Detektion mittels Spektroskopie im Allgemeinen und der Detektion unter Anwendung von REEMAP wurden erforscht und diskutiert. Ein Ergebnis dieser Arbeit ist, dass acht Seltenerdoxid Spektren eindeutig detektierbare Absorptionsbanden zeigen, die für eine Seltenerddetektion verwendet werden können. Zusätzlich können die spektralen Merkmale von Eisenoxiden, eisenhaltigen Sulfaten, Kalzit und Kaolinit verwendet werden, um metasomatische Alterationszonen und die Erzgänge zu erkennen. Eines der wichtigsten Ergebnisse dieser Doktorarbeit ist die Entwicklung der REEMAP Methode. Vor allem für verrauschte hyperspektrale Bilder zeigten die Ergebnisse unter der Verwendung von REEMAP eine höhere Detektionswahrscheinlichkeit. Neben dem Signal-zu-Rausch-Verhältnis des Bildes, sind die davon abhängige spektrale Auflösung, überdeckende Materialien, atmosphärische Effekte und Aufnahmen unter suboptimalen Lichtverhältnissen als weitere wichtige Limitation der Seltenerd-Detektion zu nennen. Ein weiteres wichtiges Ergebnis dieser Doktorarbeit ist, dass der zukünftige EnMAP Satellit (mit seinem aktuell veröffentlichten Spezifikationen, Juni 2015) theoretisch in der Lage sein wird die Absorptionsbanden von Erbium, Dysprosium, Holmium, Neodym, Europium, Thulium und Samarium zu detektieren. Meine Dissertation stellt eine neue fernerkundliche Methode (REEMAP) vor, die zur weiträumigen und schnellen hyperspektralen Detektion von seltenen Erden verwendet werden kann und somit hilfreich bei der Exploration seltener Erden sein kann. KW - remote sensing KW - rare earth elements KW - hyperspectral KW - EnMAP satellite KW - Fernerkundung KW - Seltenerdelemente KW - seltene Erden KW - Hyperspektral KW - EnMAP Satellit Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-85363 ER - TY - JOUR A1 - Bösche, Nina Kristine A1 - Rogass, Christian A1 - Lubitz, Christin A1 - Brell, Maximilian A1 - Herrmann, Sabrina A1 - Mielke, Christian A1 - Tonn, Sabine A1 - Appelt, Oona A1 - Altenberger, Uwe A1 - Kaufmann, Hermann T1 - Hyperspectral REE (Rare Earth Element) Mapping of Outcrops-Applications for Neodymium Detection JF - Remote sensing N2 - In this study, an in situ application for identifying neodymium (Nd) enriched surface materials that uses multitemporal hyperspectral images is presented (HySpex sensor). Because of the narrow shape and shallow absorption depth of the neodymium absorption feature, a method was developed for enhancing and extracting the necessary information for neodymium from image spectra, even under illumination conditions that are not optimal. For this purpose, the two following approaches were developed: (1) reducing noise and analyzing changing illumination conditions by averaging multitemporal image scenes and (2) enhancing the depth of the desired absorption band by deconvolving every image spectrum with a Gaussian curve while the rest of the spectrum remains unchanged (Richardson-Lucy deconvolution). To evaluate these findings, nine field samples from the Fen complex in Norway were analyzed using handheld X-ray fluorescence devices and by conducting detailed laboratory-based geochemical rare earth element determinations. The result is a qualitative outcrop map that highlights zones that are enriched in neodymium. To reduce the influences of non-optimal illumination, particularly at the studied site, a minimum of seven single acquisitions is required. Sharpening the neodymium absorption band allows for robust mapping, even at the outer zones of enrichment. From the geochemical investigations, we found that iron oxides decrease the applicability of the method. However, iron-related absorption bands can be used as secondary indicators for sulfidic ore zones that are mainly enriched with rare earth elements. In summary, we found that hyperspectral spectroscopy is a noninvasive, fast and cost-saving method for determining neodymium at outcrop surfaces. Y1 - 2015 U6 - https://doi.org/10.3390/rs70505160 SN - 2072-4292 VL - 7 IS - 5 SP - 5160 EP - 5186 PB - MDPI CY - Basel ER - TY - GEN A1 - Bösche, Nina Kristine A1 - Rogass, Christian A1 - Lubitz, Christin A1 - Brell, Maximilian A1 - Herrmann, Sabrina A1 - Mielke, Christian A1 - Tonn, Sabine A1 - Appelt, Oona A1 - Altenberger, Uwe A1 - Kaufmann, Hermann T1 - Hyperspectral REE (Rare Earth Element) mapping of outcrops BT - applications for neodymium detection N2 - In this study, an in situ application for identifying neodymium (Nd) enriched surface materials that uses multitemporal hyperspectral images is presented (HySpex sensor). Because of the narrow shape and shallow absorption depth of the neodymium absorption feature, a method was developed for enhancing and extracting the necessary information for neodymium from image spectra, even under illumination conditions that are not optimal. For this purpose, the two following approaches were developed: (1) reducing noise and analyzing changing illumination conditions by averaging multitemporal image scenes and (2) enhancing the depth of the desired absorption band by deconvolving every image spectrum with a Gaussian curve while the rest of the spectrum remains unchanged (Richardson-Lucy deconvolution). To evaluate these findings, nine field samples from the Fen complex in Norway were analyzed using handheld X-ray fluorescence devices and by conducting detailed laboratory-based geochemical rare earth element determinations. The result is a qualitative outcrop map that highlights zones that are enriched in neodymium. To reduce the influences of non-optimal illumination, particularly at the studied site, a minimum of seven single acquisitions is required. Sharpening the neodymium absorption band allows for robust mapping, even at the outer zones of enrichment. From the geochemical investigations, we found that iron oxides decrease the applicability of the method. However, iron-related absorption bands can be used as secondary indicators for sulfidic ore zones that are mainly enriched with rare earth elements. In summary, we found that hyperspectral spectroscopy is a noninvasive, fast and cost-saving method for determining neodymium at outcrop surfaces T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 350 KW - rare earth elements KW - imaging spectroscopy KW - neodymium KW - hyperspectral KW - HySpex KW - remote sensing KW - Fen complex Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400171 ER - TY - JOUR A1 - Mielke, Christian A1 - Bösche, Nina Kristine A1 - Rogass, Christian A1 - Kaufmann, Hermann A1 - Gauert, Christoph T1 - New geometric hull continuum removal algorithm for automatic absorption band detection from spectroscopic data JF - Remote sensing letters : an official journal of the Remote Sensing and Photogrammetry Society N2 - Modern imaging spectrometers produce an ever-growing amount of data, which increases the need for automated analysis techniques. The algorithms employed, such as the United States Geological Survey (USGS) Tetracorder and the Mineral Identification and Characterization Algorithm (MICA), use a standardized spectral library and expert knowledge for the detection of surface cover types. Correct absorption feature definition and isolation are key to successful material identification using these algorithms. Here, a new continuum removal and feature isolation technique is presented, named the 'Geometric Hull Technique'. It is compared to the well-established, knowledge-based Tetracorder feature database together with the adapted state of the art techniques scale-space filtering, alpha shapes and convex hull. The results show that the geometric hull technique yields the smallest deviations from the feature definitions of the MICA Group 2 library with a median difference of only 8nm for the position of the features and a median difference of only 15% for the feature shapes. The modified scale-space filtering hull technique performs second best with a median feature position difference of 16nm and a median difference of 25% for the feature shapes. The scale-space alpha hull technique shows a 23nm median position difference and a median deviation of 77% for the feature shapes. The geometric hull technique proposed here performs best amongst the four feature isolation techniques and may be an important building block for next generation automatic mapping algorithms. Y1 - 2015 U6 - https://doi.org/10.1080/2150704X.2015.1007246 SN - 2150-704X SN - 2150-7058 VL - 6 IS - 2 SP - 97 EP - 105 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Mielke, Christian A1 - Bösche, Nina Kristine A1 - Rogass, Christian A1 - Kaufmann, Hermann A1 - Gauert, Christoph A1 - de Wit, Maarten T1 - Spaceborne mine waste mineralogy monitoring in South Africa, applications for modern push-broom missions: Hyperion/OLI and EnMAP/Sentinel-2 JF - Remote sensing N2 - Remote sensing analysis is a crucial tool for monitoring the extent of mine waste surfaces and their mineralogy in countries with a long mining history, such as South Africa, where gold and platinum have been produced for over 90 years. These mine waste sites have the potential to contain problematic trace element species (e. g., U, Pb, Cr). In our research, we aim to combine the mapping and monitoring capacities of multispectral and hyperspectral spaceborne sensors. This is done to assess the potential of existing multispectral and hyperspectral spaceborne sensors (OLI and Hyperion) and future missions, such as Sentinel-2 and EnMAP (Environmental Mapping and Analysis Program), for mapping the spatial extent of these mine waste surfaces. For this task we propose a new index, termed the iron feature depth (IFD), derived from Landsat-8 OLI data to map the 900-nm absorption feature as a potential proxy for monitoring the spatial extent of mine waste. OLI was chosen, because it represents the most suitable sensor to map the IFD over large areas in a multi-temporal manner due to its spectral band layout; its (183 km x 170 km) scene size and its revisiting time of 16 days. The IFD is in good agreement with primary and secondary iron-bearing minerals mapped by the Material Identification and Characterization Algorithm (MICA) from EO-1 Hyperion data and illustrates that a combination of hyperspectral data (EnMAP) for mineral identification with multispectral data (Sentinel-2) for repetitive area-wide mapping and monitoring of the IFD as mine waste proxy is a promising application for future spaceborne sensors. A maximum, absolute model error is used to assess the ability of existing and future multispectral sensors to characterize mine waste via its 900-nm iron absorption feature. The following sensor-signal similarity ranking can be established for spectra from gold mining material: EnMAP 100% similarity to the reference, ALI 97.5%, Sentinel-2 97%, OLI and ASTER 95% and ETM+ 91% similarity. KW - mine waste KW - spatial extent KW - gold KW - platinum KW - South Africa KW - EnMAP KW - OLI KW - Hyperion KW - Sentinel-2 KW - iron feature depth (IFD) Y1 - 2014 U6 - https://doi.org/10.3390/rs6086790 SN - 2072-4292 VL - 6 IS - 8 SP - 6790 EP - 6816 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mielke, Christian A1 - Muedi, T. A1 - Papenfuss, Anne A1 - Bösche, Nina Kristine A1 - Rogass, C. A1 - Gauert, C. D. K. A1 - Altenberger, Uwe A1 - de Wit, M. J. T1 - Multi- and hyperspectral spaceborne remote sensing of the Aggeneys base metal sulphide mineral deposit sites in the Lower Orange River region, South Africa JF - South African Journal of Geology N2 - New tools and algorithms for geological femote Sensing are developed and verified at test sites throughout the world in preparation of the German hyperspectral satellite Mission (EnMAP), which is an Environmental Mapping and Analysis Program. The aggeneys Cu-Pb-Zn deposit, situated in the arid north western part of South Africa, represents a unique field laboratory for testing these new tools. Here spaceborne hyperspectral data covering the Swartberg, and hyperspectral spaceborne data can be demonkrated, such as the Iron Feature Depth index (IFD), which has recently been proposed for mine waste mapping in the North West Province of South Africa and for gossan detection at Haib River in South Namibia. The work presented here explores the potential of the IFD for gossan mapping and characterization at Gamsberg and Big Syncline, from EO-1 ALI and Landsat-8 OLI data together with mineral maps from expert systems such as the United States Geological Survey (USGS) Material Identification and Characterization Algorithm (MICA), and first results from EnMAPs EnGeoMAP algorithm. Field spectroscopic measurements and field sampling were carried out to validate and calibrate the results from the expert systems and the IFD. This ground truthing is a necessary complementary step to link the results from the expert systems and the IFD to in-situ field spectroscopy. Future mineral exploration initiatives may benefit from the techniques described here, because they can significantly narrow the expensive, exploration activities such as hyperspectral airborne data, field activities and drilling, by identifying the most promising mineral anomalies in an area from the spaceborne data. Y1 - 2016 U6 - https://doi.org/10.2113/gssajg.119.1.63 SN - 1012-0750 SN - 1996-8590 VL - 119 SP - 63 EP - 76 PB - Geological Society of South Africa CY - Marshalltown ER - TY - JOUR A1 - Mielke, Christian A1 - Rogass, Christian A1 - Bösche, Nina Kristine A1 - Segl, Karl A1 - Altenberger, Uwe T1 - EnGeoMAP 2.0-Automated Hyperspectral Mineral Identification for the German EnMAP Space Mission JF - Remote sensing N2 - Algorithms for a rapid analysis of hyperspectral data are becoming more and more important with planned next generation spaceborne hyperspectral missions such as the Environmental Mapping and Analysis Program (EnMAP) and the Japanese Hyperspectral Imager Suite (HISUI), together with an ever growing pool of hyperspectral airborne data. The here presented EnGeoMAP 2.0 algorithm is an automated system for material characterization from imaging spectroscopy data, which builds on the theoretical framework of the Tetracorder and MICA (Material Identification and Characterization Algorithm) of the United States Geological Survey and of EnGeoMAP 1.0 from 2013. EnGeoMAP 2.0 includes automated absorption feature extraction, spatio-spectral gradient calculation and mineral anomaly detection. The usage of EnGeoMAP 2.0 is demonstrated at the mineral deposit sites of Rodalquilar (SE-Spain) and Haib River (S-Namibia) using HyMAP and simulated EnMAP data. Results from Hyperion data are presented as supplementary information. KW - EnMAP KW - Hyperion KW - EnGeoMAP 2 KW - 0 KW - mineral mapping KW - imaging spectroscopy Y1 - 2016 U6 - https://doi.org/10.3390/rs8020127 SN - 2072-4292 VL - 8 SP - 392 EP - 414 PB - MDPI CY - Basel ER -