Chinese Gaofen-5 (GF-5) satellite is the world's first full-spectrum hyperspectral satellite to achieve comprehensive observations of the atmosphere and land. The Advanced Hyperspectral Imager (AHSI) carried by GF-5 can acquire 330- chanel imagery covering 390~2500 nm. However, the application of GF-5 AHSI imagery in uranium exploration is currently less. In this paper, the AHSI imagery was used for prospecting uranium mineralization in the Weijing, Inner Mongolia, China. The matched filter (MF) and threshold segmentation were used for mapping goethite, Al-high, Al- medium and Al-poor sericite. And the principal component analysis (PCA) and gray-level co-occurrence matrix (GLCM) were used to extract the texture information of the study area. Subsequently, combined with geological information, the relationship between alteration information, texture complexity and uranium mineralization was discussed, and it was pointed out that goethite, Al-medium, Al-poor , and Al-high sericite and texture complexity in this area can be used as indicators of uranium mineralization. Finally, two prospects were delineated, which will guide the follow-up uranium exploration in this area and promote the application of GF-5 AHSI data.
In order to study the alteration extraction method and effect of GF-5 Visual and infrared spectral imager (VIMS), this image was used as the data source. On the basis of analyzing the spectral characteristics of typical altered minerals, the principal component analysis (PCA) method was used to extract iron-stained and hydroxyl alteration, and the results were compared with those from Landsat 5 TM image. The results show that: the alteration information extracted from VIMS image is consistent with the alteration extracted from TM image, and it is more accurate; the quality of VIMS image is worse than that of TM image, which affects the result of alteration extraction. Therefore, attention should be paid to the selection of VIMS image in practical application.
Drill core is very important for researchers to study lithospheric structure. However, how to save cores in good condition as well as how to satisfy the need of studying drill cores anytime and anywhere as we want are big questions. Thus, numerical images of drill cores are very necessary. Hyperspectral images have lots of advantages, for they can provide both true color images and hyperspectral messages. True color images can be used for direct observation and study. And hyperspectral messages can be used for mineral identification. In practical use, there are distortions in the scanned hyperspectral images, so correction method is in great need. A geometric and luminance correction method is raised in this paper, and results show that the correction method works well. For the sake of observation, three-dimension display is more convenient. This paper provides an implementation method of 3D display. At last, this paper provides a method for extracting mineral alteration data. Through the methods above, hyperspectral images are useful and feasible in the digital record of drill cores.
In order to study the tectonic characteristics and its relationship with uranium mineralization in Weijing area of Inner Mongolia, the remote sensing technique and visual interpretation are applied to interpret the linear structures in Weijing area with GF-2 remote sensing data, based on the atmospheric correction and another preprocessing. The distribution regularities of linear structures can be got from the field geological examination and the available geological data. The results indicates that the intersecting areas of NE-NEE trending structure F12 and NNE trending structure F11 with EW or NW trending structures are the favorable uranium metallogenic regions. The NE-NEE trending structure F12 and NNE trending structure F11 are the most important ore-controlling structures in the area.
Hyperspectral HyMap image with synchronous in-situ spectral data were used to survey the environmental condition in Shenzhen of South China. HyMap image was measured with 3.5m spatial resolution and 15nm spectral resolution from 0.44μm-2.5μm and corrected with Modtran5 model and synchronous solar illuminance and atmospheric visibility to the ground. The spectra of rocks, soils, water and vegetation were obtained by ASD spectrometer in reflectance. Both the fresh granite and eroded sandy soil was found with absorption at 2200nm±in-situ spectra, but the weathered granite and sandy soil have another absorption at 880nm~940 nm. Polluted water with high ammonia nitrogen and phosphorous and BOD5 get the strongest reflectance at 550 ~570nm, while polluted water of high CODcr and heavy metal ions content get the peak reflectance at 450~490nm. The in-situ spectra was resampled in wavelength range and spectral resolution to that of Hymap sensor for image classification with SAM algorithm, the unpaved granite among cement the paved mine pits , the newly excavated land surface and the eroded soil was mapped out with the accuracy over 95%. We also discriminate the artificial forest from the natural with the spectral endmember extracted from the image.
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