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In flight MTF monitoring and compensation for CCD camera on CBERS-02

Science China(Technological Sciences) 2005年第S2期48卷 29-43页

作者： GU Xingfa1,2,3, LI Xiaoying1,2,4, MIN Xiangjun5, YU Tao1,2, SUN Jijuan5, ZENG Yong1,2,4, XU Hua1,2 & GUO Ding2,6 1. State Key Laboratory of remote sensing Science, Jointly Sponsored by the Institute of remote sensing Applications of Chinese Academy of Sciences and Beijing Normal University, Beijing 100101, China 2. The center for National Spaceborne Demonstration, Beijing 100101, China 3. Institut National de la Recherche Agronomique, Climat Sol Environnement, 84914 Avignon, France 4. Graduate University of Chinese Academy of Sciences, Beijing 100039, China 5. China center for Resource Satellite data and Application, Beijing 100830, China 6. University of Electronic Science and Technology of China, Chengdu 610054, China State Key Laboratory of remote sensing Science Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University Beijing China The center for National Spaceborne Demonstration Beijing China Institut National de la Recherche Agronomique Climat Sol Environnement Avignon France Graduate University of Chinese Academy of Sciences Beijing China China center for Resource Satellite data and Application Beijing China University of Electronic Science and Technology of China Chengdu China

In this article, the approach of simulating ideal tarp scene was proposed to determine the MTF for CCD camera on CBERS-02. The MTF acquired from this technique was compared to those from some common methods. MTFs achieved from different approaches were employed to compensate the CCD images based on three restoration algorithms: the iterative method, the Wiener filter and the modified inverse filter (MIF). The two-dimensional MTF was established with the value at frequency 0.5 for 45° directional MTF as the value at its four corners. This article addressed the variations of the restored CCD images with different techniques of constructing two-dimensional MTF, restoring algorithms and determining the in-flight MTFs. Results showed images restored with the MTF determined from the technique of simulating ideal tarp scene represent the real scene best. And the restoration technique based on the MIF would produce better restored images than the other two techniques. This research also demonstrated that the two-dimensional MTF used for restoration should be interpolated under the control of the MTF for 45° axis, rather than by multiplying the cross-orbit MTF with along-orbit MTF.

关键词： CBERS-02 CCD MTF the technique of simulating ideal tarp scene.

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Crucial problems in the design of a terahertz tripler

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Journal of Semiconductors 2015年第8期36卷 131-135页

作者：孟进张德海蒋长宏赵鑫黄健闫大帅 Key Laboratory of Microwave remote sensing Center for Space Science and Applied Research Chinese Academy of Sciences University of Chinese Academy of Sciences

A frequency-multiplied source at the terahertz band using discrete planar Schottky diodes, which is a critical element in heterodyne instruments, has been studied by some domestic research institutions in recent years. Besides the design method, there are still many crucial problems that must be taken into consideration in the design. This article mainly discuss three aspects based on the measured data of a 225 GHz tripler that we designed. Firstly, the accuracy of the diode model concerns the reliability of the simulation results. According to the Spice parameters and the measured results, the physical size and the DC parameter of the Schottky diode can be corrected until there is a good consistency between the simulated and measured results. Secondly, the heat accumulation happens to the Schottky junction when the high input power is added. A steady-state thermal simulation is done and the results show that the hottest temperature is about 140℃ with 250 mW input power, which is safe to the diode. Lastly, some non-ideal factors are brought during the assembly process such as the uncertainty in the conductive adhesive shape and location deviation of the circuit. Furthermore, the effect on the performance of the frequency multiplier is calculated in this work.

关键词： terahertz tripler diode model heat dissipation assembly error

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A Strategy for Merging Objective Estimates of Global Daily Precipitation from Gauge Observations, Satellite Estimates, and Numerical Predictions

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Advances in Atmospheric Sciences 2016年第7期33卷 889-904页

作者： Suping NIE Tongwen WU Yong LUO Xueliang DENG Xueli SHI Zaizhi WANG Xiangwen LIU Jianbin HUANG National Climate center China Meteorological Administration center for Earth System Science Tsinghua University Key Laboratory of Atmospheric Science and Satellite remote sensing Anhui Institute of Meteorology

This paper describes a strategy for merging daily precipitation information from gauge observations, satellite estimates （SEs）, and numerical predictions at the global scale. The strategy is designed to remove systemic bias and random error from each individual daily precipitation source to produce a better gridded global daily precipitation product through three steps. First, a cumulative distribution function matching procedure is performed to remove systemic bias over gauge-located land areas. Then, the overall biases in SEs and model predictions （MPs） over ocean areas are corrected using a rescaled strategy based on monthly precipitation. Third, an optimal interpolation （OI）-based merging scheme （referred as the HL-OI scheme） is used to combine unbiased gahge observations, SEs, and MPs to reduce random error from each source and to produce a gauge--satellite-model merged daily precipitation analysis, called BMEP-d （Beijing Climate center Merged Estimation of Precipitation with daily resolution）, with complete global coverage. The BMEP-d data from a four-year period （2011- 14） demonstrate the ability of the merging strategy to provide global daily precipitation of substantially improved quality. Benefiting from the advantages of the HL-OI scheme for quantitative error estimates, the better source data can obtain more weights during the merging processes. The BMEP-d data exhibit higher consistency with satellite and gauge source data at middle and low latitudes, and with model source data at high latitudes. Overall, independent validations against GPCP-1DD （GPCP one-degree daily） show that the consistencies between B MEP-d and GPCP-1DD are higher than those of each source dataset in terms of spatial pattern, temporal variability, probability distribution, and statistical precipitation events.

关键词： global daily precipitation multi-source merging strategy bias correction quantitative error estimation

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Population spatialization with pixel-level attribute grading by considering scale mismatch issue in regression modeling

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Geo-Spatial Information Science 2022年第3期25卷 365-382页

作者： Yuao Mei Zhipeng Gui Jinghang Wu Dehua Peng Rui Li Huayi Wu Zhengyang Wei School of remote sensing and Information Engineering Wuhan UniversityWuhanChina State Key Laboratory of Information Engineering in Surveying Mapping and Remote SensingWuhan UniversityWuhanChina Collaborative Innovation center of Geospatial Technology Wuhan UniversityWuhanChina Institute for Computational and Mathematical Engineering Stanford UniversityStanfordCAUSA

Population spatialization is widely used for spatially downscaling census population data to *** core idea of modern population spatialization is to establish the association between ancillary data and population at the administrative-unit-level(AUlevel)and transfer it to generate the gridded ***,the statistical characteristic of attributes at the pixel-level differs from that at the AU-level,thus leading to prediction bias via the cross-scale modeling(*** mismatch problem).In addition,integrating multi-source data simply as covariates may underutilize spatial semantics,and lead to incorrect population disaggregation;while neglecting the spatial autocorrelation of population generates excessively heterogeneous population distribution that contradicts to real-world *** address the scale mismatch in downscaling,this paper proposes a Cross-Scale Feature Construction(CSFC)*** specifically,by grading pixel-level attributes,we construct the feature vector of pixel grade proportions to narrow the scale differences in feature representation between AU-level and ***,fine-grained building patch and mobile positioning data are utilized to adjust the population weighting layer generated from POI-density-based regression *** filtering is furtherly adopted to model the spatial autocorrelation effect of population and reduce the heterogeneity in population caused by pixel-level attribute *** the comparison with traditional feature construction method and the ablation experiments,the results demonstrate significant accuracy improvements in population spatialization and verify the effectiveness of weight correction ***,accuracy comparisons with WorldPop and GPW datasets quantitatively illustrate the advantages of the proposed method in fine-scale population spatialization.

关键词： Random forest(RF) point of interests(POIs) mobile positioning data natural breaks spatial filtering population mapping dasymetric downscaling

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Desertification in the Mu Us Sandy Land in China:Response to climate change and human activity from 2000 to 2020

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Geography and Sustainability 2022年第2期3卷 177-189页

作者： Xin Wang Jinling Song Zhiqiang Xiao Jing Wang Fangze Hu State Key Laboratory of remote sensing Science Jointly Sponsored by Beijing Normal University and Institute of Remote Sensing and Digital Earth of Chinese Academy of SciencesBeijing 100875China Beijing Engineering Research center for Global Land remote sensing Products Institute of Remote Sensing Science and EngineeringFaculty of Geographical ScienceBeijing Normal UniversityBeijing 100875China

China is a country largely affected by *** main purpose of this article is to analyze interannual and seasonal changes in fractional vegetation cover(FVC)in the Mu Us Sandy Land(MUSL).It uses fused remote sensing data to quantitatively analyze the response of FVC to climate change and human *** results showed that desertification in the MUSL had improved over the past 20 *** V desertification decreased from more than 60%in 2000 to about 15%in *** some years,degradation appeared to be affected by climate factors and human activity,especially in the northwestern portion of the study *** FVC in summer was slightly higher than that in autumn and far higher than recorded in spring and ***,the northwestern and central parts of the study area were unstable,with high coefficients of *** gradually increased from northwest to southeast,and areas with the fastest increase in FVC were concentrated along the eastern and southern edges of the study *** correlations between FVC and precipitation and dryness were slightly pos-itive,but the correlation between FVC and temperature showed regional *** increase of population density is not a key factor limiting the growth of vegetation;the policy of“grazing prohibition,grazing rest,and rotational grazing”has allowed the restoration of vegetation;and afforestation is an effective way to promote the increase in FVC.

关键词： Mu Us Sandy Land(MUSL) Mann-Kendall test STARFM model

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HJ-1A HSI on-orbit radiometric calibration and validation research

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Science China(Technological Sciences) 2010年第11期53卷 3119-3128页

作者： GAO HaiLiang GU XingFa YU Tao GONG Hui LI JiaGuo LI XiaoYing State Key Laboratory of remote sensing Science Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal UniversityBeijing 100101China Graduate University of Chinese Academy of Sciences Beijing 100039China center for National Spaceborne Demonstration Beijing 100101China

The calibration experiment data at Dunhuang radiometric calibration site in October, 2008 were used to achieve the on-orbit radiometric calibration for HJ-1A hyper spectral imager (HSI). Two other field experiments data were used to validate the Dunhuang calibration results. One field experiment took place in Inner-Mongolia, China in September, 2008, and the other field experiment took place in Lake Frome, Australia in February, 2009. Finally, the ‘confidence interval of calibration error’ concept was put forward for quantitatively computing the calibration coefficient error confidence interval. The results showed that the Dunhuang calibration results in 2008 had high reliability. The confidence intervals of calibration error for all HSI channels were between 2% to 12%, which could satisfy the requirement of the HSI quantitative applications.

关键词： HJ-1A hyper spectral imager(HSI) radiometric calibration validation confidence interval

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A huge gap of the lithospheric magnetic field model in the Qinghai-Tibet Plateau-Comment on "Characteristics of the crustal magnetic anomaly and regional tectonics in the Qinghai-Tibet Plateau and the adjacent areas"

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Science China Earth Sciences 2013年第8期56卷 1623-1626页

作者： LUO Yao China Aero Geophysical Survey and remote sensing center for Land and Resources

The paper by Kang et al. discusses the characteristics of the crustal magnetic anomaly and regional tectonics of the Qinghai-Tibet Plateau and adjacent areas based on the degree 720 magnetic model of the National Geophysical data center （NGDC-720）. The lithospheric magnetic field model provides magnetic anomaly vectors at all desired locations and altitudes close to and above the Earth＇s surface.

关键词：青藏高原磁场模型区域构造岩石圈磁异常邻近地区地壳评论

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Establishment of a new tropospheric delay correction model over China area

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Science China(Physics,Mechanics & Astronomy) 2011年第12期54卷 2271-2283页

作者： SONG ShuLi ZHU WenYao CHEN QinMing LIOU YueiAn Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China center for Space and remote sensing Research National Central University Taiwan China

The tropospheric delay is one of the main error sources for radio navigation technologies and other ground-or space-based earth observation systems. In this paper, the spatial and temporal variations of the zenith tropospheric delay (ZTD), especially their dependence on altitude over China region, are analyzed using ECMWF (European Centre for Medium-Range Weather Forecast) pressure-level atmospheric data in 2004 and the ZTD series in 1999-2007 measured at 28 GPS stations from the Crustal Movement Observation Network of China (CMONC). A new tropospheric delay correction model (SHAO) is derived and a regional realization of this model for China region named SHAO-C is established. In SHAO-C model, ZTD is modeled directly by a cosine function together with an initial value and an amplitude at a reference height in each grid, and the variation of ZTD along altitude is fitted with a second-order polynomial. The coefficients of SHAO-C are generated using the meteorology data in China area and given at two degree latitude and longitude interval, featuring regional characteristics in order to facilitate a wide range of navigation and other surveying applications in and around China. Compared with the EGNOS (European Geostationary Navigation Overlay Service) model, which has been used globally and recommended by the European Union Wide Area Augmentation System, the ZTD prediction (in form of spatial and temporal projection) accuracy of the SHAO-C model is significantly improved over China region, especially at stations of higher altitudes. The reasons for the improvement are: (1) the reference altitude of SHAO-C parameters are given at the average height of each grid, and (2) more detailed description of complicated terrain variations in China is incorporated in the model. Therefore, the accumulated error at higher altitude can be reduced considerably. In contrast, the ZTD has to be calculated from the mean sea level with EGNOS and other models. Compared with the direct estim

关键词： EGNOS GPS tropospheric delay SHAO-C model ECMWF pressure-level data

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Derivation of salt content in salinized soil from hyperspectral reflectance data: A case study at Minqin Oasis, Northwest China

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Journal of Arid Land 2019年第1期11卷 111-122页

作者： QIAN Tana Atsushi TSUNEKAWA PENG Fei Tsugiyuki MASUNAGA WANG Tao LI Rui Arid Land Research center Tottori University Life and Environmental Science Shimane University Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences State Key Laboratory of remote sensing Science Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences

Soil salinization is a serious ecological and environmental problem because it adversely affects sustainable development worldwide, especially in arid and semi-arid regions. It is crucial and urgent that advanced technologies are used to efficiently and accurately assess the status of salinization processes. Case studies to determine the relations between particular types of salinization and their spectral reflectances are essential because of the distinctive characteristics of the reflectance spectra of particular salts. During April 2015 we collected surface soil samples(0–10 cm depth) at 64 field sites in the downstream area of Minqin Oasis in Northwest China, an area that is undergoing serious salinization. We developed a linear model for determination of salt content in soil from hyperspectral data as follows. First, we undertook chemical analysis of the soil samples to determine their soluble salt contents. We then measured the reflectance spectra of the soil samples, which we post-processed using a continuum-removed reflectance algorithm to enhance the absorption features and better discriminate subtle differences in spectral features. We applied a normalized difference salinity index to the continuum-removed hyperspectral data to obtain all possible waveband pairs. Correlation of the indices obtained for all of the waveband pairs with the wavebands corresponding to measured soil salinities showed that two wavebands centred at wavelengths of 1358 and 2382 nm had the highest sensitivity to salinity. We then applied the linear regression modelling to the data from half of the soil samples to develop a soil salinity index for the relationships between wavebands and laboratory measured soluble salt content. We used the hyperspectral data from the remaining samples to validate the model. The salt content in soil from Minqin Oasis were well produced by the model. Our results indicate that wavelengths at 1358 and 2382 nm are the optimal wavebands for monitoring the

关键词： salinity index soil salt content spectral reflectance waveband pairs arid regions

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remote sensing Interpretation and Extraction of Structural Information about Active Faults at Hangzhou,China,and Their Surroundings

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Journal of Earth Science 2013年第6期24卷 1056-1067页

作者：张微姚琪陈汉林杨金中 China Aero Geophysical Survey & remote sensing center for Land and Resources China Seismological Bureau Institute of Geology Department of Earth Sciences Zhejiang University

It is important to explore active faults in urban areas and their surroundings for earth- quake disaster mitigation. Satellite remote sensing techniques can play an important role in such active fault exploration. It can not only reveal the pattern of active faults and active tectonics on a macroscop- ic scale, but also monitor the occurrence, development and rules of temporal-spatial evolution of active faults. In this paper, we use the Hangzhou area as an example to introduce methods of extracting de- tailed active fault information when covered by thick unconsolidated Quaternary sediment, using im- age enhancement and image fusion etc. to improve the definition and precision of satellite images and presenting a three-dimensional （3D） image to illustrate tectono-geomorphic features along the relevant faults. We have also collected aeromagnetic anomaly data, shallow seismic exploration data and dating data, and carried out field surveys to validate the characteristics of active faults based on remote sens- ing images. The results revealed about the faults showed a high consistency with traditional geological knowledge, and demonstrate that it is feasible to explore active faults in a weakly active tectonic area by using satellite remote sensing techniques and contribute to large engineering projects and research on neotectonics.

关键词： remote sensing active faults exploration Quaternary image fusion Hangzhou Neotec-tonics.

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