Yoshiki Ninomiya

A stabilized vegetation index and several mineralogic indices defined for ASTER VNIR and SWIR data

ASTER is composed of three subsystems, each of which multispectrally observes the reflected or emitted radiation from the surface of the earth to space in VNIR (visible and near infrared), SWIR (shortwave infrared) and TIR (thermal infrared) wavelength regions, respectively. Here in this paper, problems in applying the widely used vegetation index, NDVI, to remotely sensed radiance at the sensor data without atmospheric corrections are discussed, and a stabilized vegetation index against the fluctuation factors in the radiance at the sensor data is proposed. Then, reflectance spectra of minerals in SWIR region measured in the laboratory are analyzed to define calcite index, OH-bearing altered minerals index, kaolinite index and alunite index for discriminating the minerals by ASTER-SWIR. The defined indices are applied to ASTER Level-1B radiance at the sensor data multi-temporally observing Cuprite area in Nevada, USA. Discussions are made on the results, especially on the effectiveness of the stabilized vegetation. Also, the applied results of the defined mineralogic indices are compared with the well-known geology of the area.

Lithologic mapping with multispectral ASTER TIR and SWIR data

ASTER, launched in December, 1999, composed of three subsystems, each of which multispectrally observes the reflected or emitted radiation from the surface of the earth to space in VNIR (visible and near infrared), SWIR (shortwave infrared) and TIR (thermal infrared) wavelength regions, respectively. ASTER-VNIR has three spectral bands with a spatial resolution of 15m, and the one of which in near infrared has an along track stereo observation capability to produce high quality Digital Elevation Model (DEM). ASTER-SWIR has six spectral bands with a spatial resolution of 30m, which are mainly designed for discriminating altered minerals bearing hydroxyl group. ASTER-TIR has five spectral bands with a spatial resolution of 90m, which presents us a powerful tool for identifying quartz and carbonate minerals as well as discriminating types of silicate rocks. The author have successfully developed a robust method for detecting quartzite and carbonate rocks as well as classifying type of igneous rocks with ASTER TIR data without atmospheric corrections (Level-1B data). Here in this paper, reflectance spectra of minerals in SWIR region measured in the laboratory are analyzed to define calcite index, OH-bearing silicate index, kaolinite index and alunite index for discriminating each mineral by ASTER-SWIR. The defined indices are applied to SWIR data of ASTER Level-1B radiance at the sensor data observing Cuprite area in Nevada, USA, and the discussions are made on the results by comparing the well-known geology of the area. Also, the result of calcite index is compared with the result of applying well-characterized carbonate index defined for ASTER-TIR to clarify the strong point of each index.

Rock type mapping with indices defined for multispectral thermal infrared ASTER data: case studies

ASTER sensor aboard NASAs Terra satellite has the capability of measuring multispectral thermal infrared (TIR) emission from the earths surface to space. The author proposed indices by the combination of ASTER-TIR bands for detecting quartz and carbonate minerals, and another index to estimate the abundance of bulk SiO2 content in the surface silicate rocks, applied them to the low level ASTER radiance at the sensor data without atmospheric corrections, and showed a potential ability of the indices in a rock type mapping. This paper tries to apply the proposed method into the practical case studies using ASTER-TIR data. The study sites include ophiolitic belt zones in Oman and along Yarlun Zangbo River in Tibet. The applied results are compared with the geology of the study areas. It indicates that the new remote sensing approach proposed here would improve the quality and the cost of the geological mapping in arid and semi-arid regions.

Advanced remote lithologic mapping in ophiolite zone with ASTER multispectral thermal infrared data

ASTER is the first and the only satellite-borne imaging sensor with a capability of multispectral observation in the thermal infrared (TIR; 8 to 12 microns) spectral region at spectral, radiometric and spatial resolutions adequate for regional geological study. Most of the methods for lithologic or mineralogic mapping with multispectral TIR remote sensing data proposed so far premises to apply emissivity data as input, but methods applying Level-1B radiance at the sensor data without atmospheric corrections have an advantage in data productivity. Another advantage of the methods for Level-1B is the extendibility for Level-3A data, enables easy fusion with GIS. The author proposed Quartz Index (QI), Carbonate Index (CI) and bulk SiO2 content Index (SI) for ASTER-TIR data with theoretical and practical analyses for the applicability of Level- 1B data, improved the indices, and showed that the lithologic mapping with the indices for Level-1B data is stable against the variation of temperature and atmospheric conditions. In this paper, the method is applied to several Level-3A data scenes observing a part of Yarlung Zangbo ophiolite belt in Tibet, and the results are compared with the existing geological information to show the effectiveness of the method for achieving lower cost and higher accuracy in geological mapping, especially in mapping ultramafic rock bodies.

Satellite-derived mineral mapping and monitoring of weathering, deposition and erosion

The Earth’s surface comprises minerals diagnostic of weathering, deposition and erosion. The first continental-scale mineral maps generated from an imaging satellite with spectral bands designed to measure clays, quartz and other minerals were released in 2012 for Australia. Here we show how these satellite mineral maps improve our understanding of weathering, erosional and depositional processes in the context of changing weather, climate and tectonics. The clay composition map shows how kaolinite has developed over tectonically stable continental crust in response to deep weathering during northwardly migrating tropical conditions from 45 to 10 Ma. The same clay composition map, in combination with one sensitive to water content, enables the discrimination of illite from montmorillonite clays that typically develop in large depositional environments over thin (sinking) continental crust such as the Lake Eyre Basin. Cutting across these clay patterns are sandy deserts that developed <10 Ma and are well mapped using another satellite product sensitive to the particle size of silicate minerals. This product can also be used to measure temporal gains/losses of surface clay caused by periodic wind erosion (dust) and rainfall inundation (flood) events. The accuracy and information content of these satellite mineral maps are validated using published data.

Geomorphological changes associated with underground coal mining in the Fushun area, northeast China revealed by multitemporal satellite remote sensing data

Fushun is a famous coal-mining city in northeastern China with more than 100 years of history. Long-term underground coal mining has caused serious surface subsidence in the eastern part of the city. In this study, multitemporal and multisource satellite remote sensing data were used to detect subsidence and geomorphological changes associated with underground coal mining over a 10-year period (1996–2006). A digital elevation model (DEM) was generated through Synthetic Aperture Radar (SAR) interferometry processing using data from a pair of European Remote Sensing Satellite (ERS) SAR images acquired in 1996. In addition, a Shuttle Radar Topography Mission (SRTM) DEM obtained from data in 2000 and an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEM from 2006 were used for this study. The multitemporal DEMs indicated that the maximum vertical displacement due to subsidence was around 13 m from 1996 to 2006. Multitemporal ASTER images showed that the flooded water area associated with subsidence had increased by 1.73 km2 over the same time period. Field investigations and ground level measurements confirmed that the results obtained from the multitemporal remote sensing data agreed well with ground truth data. This study demonstrates that DEMs derived from multisource satellite remote sensing data can provide a powerful tool to map geomorphological changes associated with underground mining activities.

Spectral indices for lithologic mapping with ASTER thermal infrared data applying to a part of Beishan Mountains, Gansu, China

The ASTER sensor aboard the Terra platform has a capability of spectral measurement not only in visible and near infrared (VNIR) and shortwave infrared (SWIR) regions but also in thermal infrared (TIR) region with a spatial resolution adequate for geological applications. This paper proposes several spectral indices for rock type mapping using ASTER TIR data and applies them to a part of the Beishan Mountains in China. The result indicates that the indices are very useful in lithologic mapping.

Wide area lithologic mapping with ASTER thermal infrared data: Case studies for the regions in/around the Pamir Mountains and the Tarim basin

After the authors have proposed the mineralogical indices, e.g., Quartz Index (QI), Carbonate Index (CI), Mafic Index (MI) for ASTER thermal infrared (TIR) data, many articles have been applied the indices for the geological case studies and proved to be robust in extracting geological information at the local scale. The authors also have developed a system for producing the regional map with the indices, which needs mosaicking of many scenes considering the relatively narrow spatial coverage of each ASTER scene. The system executes the procedures very efficiently to find ASTER data covering a wide target area in the vast and expanding ASTER data archive. Then the searched ASTER data are conditioned, prioritized, and the indices are calculated before finally mosaicking the imagery. Here in this paper, we will present two case studies of the regional lithologic and mineralogic mapping of the indices covering very wide regions in and around the Pamir Mountains and the Tarim basin. The characteristic features of the indices related to geology are analysed, interpreted and discussed.

Analysis of mineral composition by infrared spectral imaging using quantum dot focal plane array sensor

In this report, mineral composition of rock samples including conglomerate, sandstone, and dolomite was analyzed by IR spectral imaging using QDIP focal plane arrays (FPAs) with a peak-responsivity wavelength of 6.5 μm (FPA 1) and 5.5 μm (FPA 2). The qualitative and quantitative analyses are presented, and the key factor that determines the quantitative precision is discussed. In the qualitative analysis, the luminance of the different components in the rock samples was compared in the image. In the FPA 1 images, the shell fossil in the conglomerate sample and the limestone in the sandstone sample were darker than the other parts of the rocks due to their low emittance at 6.5 μm. In contrast, the difference in the luminance is hardly observed in the FPA 2 images under the same conditions. In the quantitative analysis, the emittance of dolomite was measured. Ten points in the IR image were randomly selected and the average emittance was calculated. The obtained emittances were 0.544±0.012 (FPA 1) and 0.941±0.019 (FPA 2), which means the coefficient of variation of the emittance measurement is ±2.1%~2.2%. By calculating the propagation of error, the precision of thermocouples for monitoring the temperature of the rocks in the calibration contributes most significantly (73%) to the total error.

Regional lithological mapping in the Tibetan plateau and surrounding area using aster data

The development of methods for mapping lithology and structure has been the main goals of geological remote sensing research. With the successful development of mineralogic indices, e.g., Quartz Index (QI), Carbonate Index (CI), Mafic Index (MI) based on the ASTER multispectral thermal infrared (TIR) data, which have demonstrated the usefulness and effectiveness of ASTER TIR data on lithologic mapping, we have produced the regional mosaic mapping of the indices covering wide area in the semi-arid to arid regions across the globe. Here in this paper, we show the method of making the regional lithological mapping with the indices defined for ASTER data, present example results of mapping covering a part of the Tibetan Plateau and surrounding area, and then make some geological discussions on the results.