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Xu Z.-X.,Beijing Normal University | Li J.-Y.,China Institute of Land Surveying and Planning
Shuikexue Jinzhan/Advances in Water Science | Year: 2010

The paper reviews and summaries the state-of-the-art, major progresses, and future perspectives in hydrological sciences. The study reveals that the societal need is the fundamental driving force and the advance in science and technology is the source for the development of hydrological sciences. In hydrological sciences, land surface hydrological processes should be investigated, as well as the water and energy exchanges among the atmosphere, land surface and groundwater. Physical processes of water transfer and movement should be investigated, as well as the chemical processes of different chemical compositions dissolved in the water. The study, in particular, the need for including the biological processes in hydrological cycle and water movement should be strengthened towards ecohydrology. At present, both ecohydrology and impact of climate change are very active in hydrological sciences under the changing environment. The theory of hydrological sciences should be further improved and developed. The socio-economic benefits of hydrological services should be enriched and strengthened in the future. Hydrological science could thus play an active role to support socio-economic development. Copyright. Source


Zuo D.-P.,Beijing Normal University | Xu Z.-X.,Beijing Normal University | Li J.-Y.,China Institute of Land Surveying and Planning | Liu Z.-F.,Beijing Normal University | Liu Z.-F.,CAS Institute of Geographical Sciences and Natural Resources Research
Shuikexue Jinzhan/Advances in Water Science | Year: 2011

The parameters in the temperature-based Hargreaves method for the estimation of potential evapotranspiration (ETP) are calibrated by the FAO Penman-Monteith method and daily data during the period 1959-2008 at 20 meteorological stations in the Weihe River basin. To study the impact of climate change on potential evapotranspiration, the projected daily maximum and minimum air temperature (Tmax/Tmin) of HadCM3 GCM under A2 and B2 scenarios are first downscaled onto local meteorological stations using the statistical downscaling model (SDSM). Using the calibrated Hargreaves method, the future ETP, Tmax and Tmin time series under A2 and B2 scenarios can then be calculated. The spatiotemporal characteristics of these series are analyzed. Results show that the calibrated Hargreaves method reproduces well the observed potential evapotranspiration at each of the 20 meteorological stations; upward trends in daily Tmax and Tmin and annual ETP could be significant compared to that of the baseline period 1961-1990 under both scenarios; the increase in meteorological variables would be greater under A2 than B2; over different regions of the Wei River basin, the annual ETP could be gradually increasing for the three future periods, the 2010-2039, the 2040-2069 and the 2070-2099; and the greatest increase of ETP could be expected in the south bank of the basin, while the lowest increase might be found in the north bank. Source


Wu R.,Hohai University | He X.,Hohai University | Wang J.,China Institute of Land Surveying and Planning
Journal of Applied Remote Sensing | Year: 2015

The new launched ZiYuan-3 (ZY-3) satellite with multispectral (MS) bands and a panchromatic (PAN) band has presented a new opportunity to assess image fusion methods for coastal wetland mapping. This study focuses on image fusion quality assessment through both quantitative spectral and spatial quality analysis and object-oriented classification comparison. Various methods for pan-sharpening ZY-3 MS and PAN bands are tested, including generalized intensity-hue-saturation transform (GIHS), à trous wavelet transform (AWT), nonsubsampled contourlet transform (NSCT), and a combination of NSCT with GIHS (NSCT-GIHS). Spectral fidelity and spatial preservation of fused bands are compared with the original MS bands as reference, and spatial information injections of fused bands are compared with the resampled PAN band as reference. The fusion results demonstrate that, on average, the NSCT-GIHS method has the best performance on spectral fidelity and spatial preservation as well as spatial information injection. The near-infrared (NIR) band has the best spatial information injection in terms of entropy and cross-entropy indices, whereas the NIR band has the best spatial preservation in terms of entropy and structure similarity indices. The classification results show that NSCT-GIHS method also obtains the highest overall accuracy (96%) and Kappa coefficient (0.9425); this is in agreement with the quantitative analysis. © 2015 Society of Photo-Optical Instrumentation Engineers. Source


Wu R.,Hohai University | He X.,Hohai University | Wang J.,China Institute of Land Surveying and Planning
Gaojishu Tongxin/Chinese High Technology Letters | Year: 2015

The study was conducted to assess the fusion of the ZY-3 satellite's multi-spectral (MS) images and panchromatic (PAN) images from the angles of coastal wetland classification comparison and quantitative analysis. Four MS-PAN fusion methods of generalized intensity-hue saturation (GIHS) transformation, à trous wavelet transformation (AWT), nonsub sampled Contourlet transformation (NSCT) and NSCT-GIHS (NSCT-GIHS combination) were used to achieve the fusion of ZY-3 images, and spectral information indices as well as spatial information indices were utilized to quantitatively assess the quality of the fusion products. The assessment results showed that the fusion quality of the NSCTGIHS was superior to that of other three fusion methods from the spectral and spatial fidelity view. Meanwhile, an object-based classification approach was developed for coastal wetland mapping. The classification results demonstrated that NSCTGIHS based image obtained the highest overall accuracy and Kappa coefficient, 96% and 0.9425. It was obvious that wetland classification result was consistent with quantitative assessment. ©, 2015, Inst. of Scientific and Technical Information of China. All right reserved. Source


Wang J.,China Institute of Land Surveying and Planning | Wang J.,Hong Kong Polytechnic University | Liu A.,China Institute of Land Surveying and Planning | Li S.,Hong Kong Polytechnic University | Chen Y.,Hong Kong Polytechnic University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

China's land resources are extremely scarce. There is a pressing need for building the technical system of land survey and monitoring for detail knowledge about the current situation of land use, land value and land property right of each piece of land in the whole country for land use and management. Many works of land survey and monitoring in China have been finished for providing references directly for the macro decision-making and making the national economic and social development planning. However, there were limits in integrity, systemization, and standardization, and some of works about survey and monitoring were carried out in the early period and their results were not updated in time. The purpose of the paper is to establish the framework of systemized technical system of land survey and monitoring for guidance of future national work of land survey and monitoring. The study was through comparing and analyzing the past and ongoing projects of land survey and monitoring. Results indicated that the technical system is constituted by 5 sub-systems. The system will integrate land survey and monitoring, land evaluation, and information sharing service into a whole. The regional arrangement of land survey and monitoring was proposed. Seven implementation regions of land survey and monitoring were divided, including the northeastern region, eastern coastal region, central region, southwestern region, northwestern region, Xinjiang Urgur region, and Qinghai-Tibetan region. The survey and monitoring objectives and contents in each region are different. The zoning is for guidance of the future project arrangement about national land survey and monitoring in China based on land resources background and economic development demands. © 2010 Copyright SPIE - The International Society for Optical Engineering. Source

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