Qinjun Wang

Application of remote sensing for investigating mining geological hazards

Abstract To investigate geological mining hazards using digital techniques such as high-resolution remote sensing, a semi-automatically geological mining hazards extraction method is proposed based on the case of the Shijiaying coal mine, located in Fangshan District, Beijing, China. In the method, the vegetation is first removed using the normalized difference vegetation index (NDVI) on the GeoEye-1 data. Then, geological mining hazards interpretation features are determined after color enhancement using principal component analysis (PCA) transformation. Bitmaps mainly covered by geological mining hazards are isolated by masking operation in the environment for visualizing images software. Next, each bitmap is classified into a two-valued imagery using support vector machine algorithm. In the two-valued imagery, 1 denotes the geological mining hazards, while 0 denotes none. Afterwards, the two-valued imagery is converted into a vector graph by corresponding functions in the ArcGIS software and no geological mining hazards regions in the vector graph are deleted manually. Finally, the correlation between factors (such as mining activity, lithology, geological structure, and slope) and geological mining hazards is analyzed using a logistic regression and a hazardous-area forecasting model is built. The results of field verification show that the accuracy of the geological mining hazards extraction method is 98.1% and the results of the hazardous-area forecasting indicate that the logistic regression is an effective model in assessing geological hazard risks and that mining activity is the main contributing factor to the hazards, while geological structure, slope, lithology, roughness of the surface, and aspect are the secondary.

Rock types detection and classification through the use of orthogonal subspace projection approach

In most cases especially rock types detection, the pixels in remote sensing image are mixed, and so common methods based on pure pixels to detect target are not appropriate here. Orthogonal Subspace Projection has two important properties: one is to eliminate or suppress the undesired signals by projecting each pixel onto the space orthogonal to interfering signals, another is to detect the presence of desired signal by projecting the residuals onto the space of interesting signal and maximizing the signal-to-noise ratio (SNR). It can be used simultaneously on mixed pixels and the pure ones. Using Thematic Mapper (TM) data to classify different rock types shows OSP to perform well.

Landslide susceptibility mapping based on GIS modle on Shicheng Jiangxi province, china

A GIS model-information index model was presented for landslide susceptibility mapping on Shicheng, Jiangxi province, China.140 landslides were identified from SPOT6 fusion image with 1.5 meters resolution, and they were verified by field investigation. Application of the information index model showed that the landslides more likely occur in areas nearby the road, the river and the lower vegetation covery. The high elevation accuracy of 71% was reached using a receiver operating characteristic (ROC). The result indicates that the northeast and parts of the south of Shicheng County are highly susceptible to damages from landslides, which provides useful information for disaster management and decision making.

Hyperspectral Soil Dispersion Model for the Source Region of the Zhouqu Debris Flow, Gansu, China

A new hyperspectral soil dispersion model was established by using multivariable linear regression based on experimentally derived soil dispersion data and hyperspectral field spectra of soil components. The coefficient of determination for the model is 0.8084, which shows that the model effectively reproduced soil dispersion. Those bands that were relevant to soil dispersion included 370, 377, 398, 410, 570, 1918, 1933, 2392, 2401, 2444, and 2448 nm, which identified soil components and their adsorbed ions. The correlation between soil spectral bands and soil components indicates that calcite and clay minerals were the main factors that caused soil to be dispersive because they are easily dissolved in water. This result provides a scientific basis for countering soil dispersion and reducing the occurrence of debris flows. The spectral bands determined by this model may also be relevant to air- or satellite-borne hyperspectral remote sensing in the future.

Estimation of surface roughness in aird alluvial fan using SAR data

The geomorphic features of alluvial fans in arid and semi-arid areas can contain vast amounts of information for the study of paleoclimatic and paleoenvironmental changes. Taking the Shule River Alluvial Fan (SRAF) as study area, the research of surface roughness estimation, one of the important geomorphic features of the arid and semi-arid alluvial fans, was carried out by using Radarsat-2 polarimetric synthetic aperture radar (SAR) data in this paper. A modified roughness inversion model was developed to solve the roughness overvalued problem when the conventional models are used in arid surface of alluvial fans directly. In this model, the dielectric constant of the gravels exposed in the surface, instead of the moisture, becomes a more important influencing factor on backscattering coefficients. After comparing the results retrieved from the conventional and modified roughness invention models, the correlation coefficient increases from 0.68 to 0.85, and the absolute difference between the inversion and field measured value reduces obviously. As a result, the proposed model improves the accuracy effectively and is suitable for the roughness parameter inversion in the arid surface of alluvial fans.

Application of information index model in landslide susceptibility mapping on Tonggu Jiangxi PROVINCE, China

The case study presents an information index model for landslide susceptibility mapping in Tonggu County, Jiangxi Province, China. More than 100 landslides were identified from the 2.5-m fused SPOT imagery, and about 60 percent of them were verified in field investigation. It is proved that the landslides are more likely to occur in granite areas, which are strongly weathered, and the areas close to faults. The high elevation accuracy of 75.6% was reached using a receiver operating characteristic (ROC). The result indicates that the south and parts of the northeast of Tonggu County, including Paipu-Yongning and Daduan-Guqiao Towns, are highly susceptible to damages from landslides.

A method for quickly extracting seismogeological hazards in Yingxiu, Sichuan Province, China

A method for seismogeological hazards extraction using high resolution remote sensing was proposed in the research taken the epicenter of Wenchuan earthquake-Yingxiu town as the study area. In which, making imagery was built according to the Digital Elevation Model (DEM) to remove interfering factors. Then, the masked imagery was diced into several small parts to reduce the large imageries’ inconsistency and they were used as the sources to be classified. After that, the vector conversion was performed on the classified images to mapping geological hazards. Finally, other interfering factors such as bare lands, lands covered by few vegetation and buildings on the top altitude were removed manually. For it can extract geological hazards in a short time, it is of great importance for the decision–makers and rescuers to know the damaged degree in the disaster area, especially within 72 hours after the earthquake. Therefore, it will play an important role in decision making, site rescue and hazards response planning.

A study of the deep mineralization evaluation based on field measured spectra in Wushan-copper deposit area

With the development of Hyperspectra and the method of rock-mineral information extraction, several cores were analyzed based on analytical spectral devices (ASD) and rock-mineral information extraction in Wushan-cooper deposit area. Aiming at the low accuracy of mineral identification with hyperspectral data, the present study established regional spectra library on the basis of the study area geological background, section noise filtering and fast Fourier transform processing methods. Using the rapid quantificational identification model, the rock-mineral alternation information was extracted to build core profile and 3D model to discuss the deep mineralization evaluation. Combing with the regional metallogenic background, the alteration information indicated that the ore mineral was related with multiple alteration assemblages and there may be rock mass in deep space. The Cu element contents and ore mineral were closely related with the skarnization, silicification and chloritization. It also suggested that the deposit was skarn type in less than 1000 m depth, which was affected by the sandstone. Meanwhile, in more than 1000 m depth, the deposit was controlled by composite minerallzation types, which was associated with the previous geology and mineral deposits studies. In summary，this study supported a two stage mineralization model for the Wushan-copper deposit area，namely，the first stage of synsedimentary hydrothermal exhalative stage and the second stage of magmatichydrothermal ore-forming stage.

Characteristics of the gravel size and potassium in the Ejin Alluvial Fan from remote sensing images and stratigraphic section

The Ejin Alluvial Fan (EAF), located in the north-west of China, is an important recorder of both paleoclimatic and tectonic information of the north margin of the Qinghai-Tibet Plateau. Remote sensing technics, including optical and microwave sensors, have been the key spatial observation tools to extract the surface information related to the paleoenvironment. In this paper, the gravel size and chemical element potassium K distributions of the EAF were obtained from RadarSat-2 Synthetic Aperture Radar (SAR) data and LandSat TM optical data, respectively. In addition, the stratigraphic section of the EAF was established and the corresponding geological information in the vertical direction with different periods was obtained. Combining the geological survey information and surface distribution information, it can be concluded as follows. 1) The EAF covers an area of above 30,000 km2 and may be the largest arid and semi-arid alluvial fan in the world based on the remote sensing survey. 2) Some surface parameters which are related to the paleoenvironmental change can be obtained from remote sensing data, such as the gravel size and potassium K parameters. 3) The forming process of the EAF and the corresponding environments will be understood deeply, combining the paleoenvironmental related parameters derived from remote sensing data and the geologic survey data.

A suitalbe solution for extraction of alteration anomalies from the remote sensing data: A case study of the Baogutu porphyry copper deposit intrusion, Xinjiang, China using Aster data

This paper presents a new alteration mineral mapping method based on statistical analysis of spectra. First of all, this method processes a cluster of measurement data of spectral of field samples, in order to distinguish different sample area from the overall types. Second, the results of the clustering of different mineral alterations were established their respective discriminant functions. Thus, mapping major alteration type accords with the clustered reference spectra by given remote sensing images. Finally mapping further alteration types based on the discrimant function of second step, which lead to final alteration map. This method takes full account of the different combination of alteration types, as well as the regional differences of alterations, and the establishment of the discriminant function for alteration minerals is more scientific. Moreover, we access the reliability of mapping to a certain extent. The method applied to a study area of Baogutu in Xinjiang Province, which represent a good result.