Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection

Fuzhou, China

Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection

Fuzhou, China

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Huang S.,Fuzhou University | Huang S.,Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection | Xu H.,Fuzhou University | Xu H.,Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection | And 2 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2014

As time goes by, the aged satellite sensors have made the original Calibration Parameter File (CPF) of the sensors become invalid. Typically the CPF of the Landsat-5 Thematic Mapper (TM) was modified several times since its launch in 1984, and so did the CPF of Landsat-7 Enhanced Thematic Mapper Plus (ETM+). Otherwise the accuracy of the image radiometric correction is not ensured. In this study, two scenes of Landsat TM and ETM+ images have been corrected using their CPFs issued in 2003 and 2009, respectively. These radiometrically-corrected images were then compared to see whether there was any difference between the correction results. The band-by-band comparison reveals that, except the green band of ETM+, the mean value of TM and ETM+ bands calculated with the 2009 CPF is less than that calculated with the 2003 CPF. This also has influenced on the Normalized Difference Vegetation Index (NDVI) and build-up index (IBI) computation. The difference in the mean value between the NDVIs calculated using the 2003 and 2009 CPFs amounts to 0.48%, while this figure between the IBIs can reach to 5.94%.


Xiong C.-X.,Fuzhou University | Xiong C.-X.,Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection | Lu X.-B.,CAS Institute of Mechanics | Huang W.-D.,China Academy of Building Research | Wang C.-H.,CAS Chengdu Institute of Mountain Hazards and Environment
Journal of Mountain Science | Year: 2014

Effects of heat softening on the initiation of slide surface (shear banding) in clayey slopes during fast deformation were discussed. Controlling equations considering heat, pore pressure and mechanical movement were presented. By perturbation method, the instability condition of localized zone (i.e. criterion for initiation of shear banding) for thermal related soils, such as clayey slope, was obtained. It is shown that slide surface initiates once the thermal-softening effects overcome the strain-hardening effects whether it is adiabatic or not. Without strain hardening effects, strain rate hardening obviously plays a role in initiation of shear band. During initiating process, heat is trapped inside the shear band, which leads rapidly to a pore pressure increase and fast loss of strength. The localized shear strain is concentrated in a narrow zone with a width of several centimeters at most and increases fast. This zone forms the sliding surface. Temperature can increase more than 2°C, pore pressure can increase 160% in about 0.1s inside this zone. These changes cause the fast decrease in friction-coefficient by about 36% over the initial value. That is how shear band initiated and developed in clayey slopes. © 2014, Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg.


Xu H.,Fuzhou University | Xu H.,Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection | Huang S.,Fuzhou University | Huang S.,Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection | And 2 more authors.
Advances in Space Research | Year: 2013

Worldwide urbanization has accelerated expansion of urban built-up lands and resulted in substantial negative impacts on the global environments. Precisely measuring the urban sprawl is becoming an increasing need. Among the satellite-based earth observation systems, the Landsat and ASTER data are most suitable for mesoscale measurements of urban changes. Nevertheless, to date the difference in the capability of mapping built-up land between the two sensors is not clear. Therefore, this study compared the performances of the Landsat-7 ETM+ and ASTER sensors for built-up land mapping in the coastal areas of southeastern China. The comparison was implemented on three date-coincident image pairs and achieved by using three approaches, including per-band-based, index-based, and classification-based comparisons. The index used is the Index-based Built-up Index (IBI), while the classification algorithm employed is the Support Vector Machine (SVM). Results show that in the study areas, ETM+ and ASTER have an overall similar performance in built-up land mapping but also differ in several aspects. The IBI values determined from ASTER were consistently higher than from ETM+ by up to 45.54% according to percentage difference. The ASTER also estimates more built-up land area than ETM+ by 5.9-6.3% estimated with the IBI-based approach or 3.9-6.1% with the SVM classification. The differences in the spectral response functions and spatial resolution between relative spectral bands of the two sensors are attributed to these different performances. © 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.


Xu H.,Fujian Provincial Key Laboratory of Remote Sensing of Soil Erosion and Disaster Protection | Xu H.,Fuzhou University
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

Severe soil loss has caused ecological degradation for the global ecosystem, thus it is a major problem facing the world today. Timely and fast monitoring ecological changes in soil loss regions has become an increasing concern. This paper develops a remote sensing assessment method of soil erosion-induced changes in regional ecological quality based ecological index (RSEI). The proposed index combines four indicators from existing remote-sensing indices/components to represent greenness, dryness, wetness and heat, which are the important ecological indicators frequently used in assessing regional ecological status. The four remote-sensing indices/components are the normalized difference vegetation index (NDVI), soil index (SI), wetness component of the tasseled cap transformation (Wet), and land surface temperature (LST). The principal component analysis (PCA) was utilized to compress the four indicators into one index - RSEI, in order to assess overall ecological status. The new index, RSEI, was thus constructed using the first component as it was proved to have effectively combined the most information of the four indicators. The application of the RSEI in Hetian basin area in Changting county of Fujian province, one of the most serious reddish soil erosion areas in southern China, showed that the RSEI can quantitatively assess the ecological effects of soil loss treatment in the area and easily detect spatial and temporal changes of the ecological quality through a time period from 1988 to 2010. The application utilized three Landsat TM images of 1988, 2004 and 2010. The four indicators (NDVI, SI, Wet and LST) of each year were retrieved from the images and then combined through the PCA transform to form the RSEIs for the study years. The RSEI-based analysis indicated that after a more than 20 years fight for soil loss in the area by the local people and government, the ecological quality of the area has been significantly improved. This is suggested by an increase in the mean RSEI value from 0.5 in 1988 to 0.59 in 2010, accompanied by a decrease in low level RSEI area from 66.1% to 47.7%, and an increase of high level RSEI area from 33.9% to 52.3% in this duration. Quantitative analysis reveals that the greenness indicator represented by NDVI contributes most to the RSEI change among the four indicators used for generating the index. This suggests that the biological restore of soil erosion areas by planting tree and grass is an effective way to soil-erosion treatment for Hetian basin.

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