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| 1 | Classification of hyperspectral remote sensing images using frequency spectrum similarity显示文摘An algorithm of hyperspectral remote sensing images classification is proposed based on the frequency spectrum of spectral signature.The spectral signature of each pixel in the hyperspectral image is taken as a discrete signal,and the frequency spectrum is obtained using discrete Fourier transform.The discrepancy of frequency spectrum between ground objects' spectral signatures is visible,thus the difference between frequency spectra of reference and target spectral signature is used to measure the spectral similarity.Canberra distance is introduced to increase the contribution from higher frequency components.Then,the number of harmonics involved in the proposed algorithm is determined after analyzing the frequency spectrum energy cumulative distribution function of ground object.In order to evaluate the performance of the proposed algorithm,two hyperspectral remote sensing images are adopted as experimental data.The proposed algorithm is compared with spectral angle mapper (SAM),spectral information divergence (SID) and Euclidean distance (ED) using the product accuracy,user accuracy,overall accuracy,average accuracy and Kappa coefficient.The results show that the proposed algorithm can be applied to hyperspectral image classification effectively. | WANG Ke GU XingFa YU Tao MENG QingYan ZHAO LiMin FENG Li | 2013 | Science China(Technological Sciences)2013，56，4： | 10 |
| 2 | Forest NPP estimation based on MODIS data under cloudless condition显示文摘Based on light-use efficiency model, an MODIS-derived daily net primary production (NPP) model was developed. In this model, a new model for the fraction of photosynthetically active radiation absorbed by vegetation (FPAR) is developed based on leaf area index (LAI) and albedo parameters, and a pho- tosynthetically active radiation (PAR) is calculated from the combination of Bird's model with aerosol optical thickness and water vapor derived from cloud free MODIS images. These two models are inte- grated into our predicted NPP model, whose most parameters are retrieved from MODIS data. In order to validate our NPP model, the observed NPP in the Qianyanzhou station and the Changbai Mountains station are used to compare with our predicted NPP, showing that they are in good agreement. The NASA NPP products also have been downloaded and compared with the measurements, which shows that the NASA NPP products underestimated NPP in the Qianyanzhou station but overestimated in the Changbai Mountains station in 2004. | CHEN LiangFu GAO YanHua LI Li LIU QinHuo GU XingFa | 2008 | Science China Earth Sciences2008，51，3： | 7 |
| 3 | Uncertainty analysis of cross-calibration for HJ-1 CCD camera显示文摘Radiometric calibration of sensor is the basis of quantitative remote sensing,and uncertainty analysis is critical to ensure the accuracy of cross-calibration.Therefore,firstly,cross-calibration formulas were improved by redefining calibration coefficient and spectral band matching factor.In these formulas,cci was redefined as the calibration coefficient of normalized apparent reflectance,and spectral band matching factor as the ratio of normalized apparent reflectance.Secondly,based on the contrast of ideal and actual conditions in cross-calibration,8 sources of cross-calibration uncertainty were proposed:calibration uncertainty of standard sensor;pixel matching uncertainty;spectral band matching factor uncertainty caused by site altitude setting error,atmospheric parameters setting error,surface spectrum source,surface bidirectional reflectance characteristic,and error of atmospheric radiative transfer model;and uncertainty caused by other factors which were not considered.Finally,the contribution of each uncertainty was further analyzed and discussed for the HJ-1 CCD camera.The results provide many valuable references for evaluating the feasibility of alternative cross-calibration measurements. | WANG Zuo XIAO PengFeng GU XingFa FENG XueZhi LI XiaoYing GAO HaiLiang LI Hui LIN JinTang ZHANG XueLiang | 2013 | Chinese Science Bulletin2013，58，7： | 3 |
| 4 | Improvement of Glacial Lakes Detection under Shadow Environment Using ASTER Data in Himalayas, Nepal显示文摘The detection of glacial lake change in the Himalayas, Nepal is extremely significant since the glacial lake change is one of the crucial indicators of global climate change in this area, where is the most sensitive area of the global climate changes. In the Himalayas, some of glacial lakes are covered by the dark mountains′ shadow because of their location. Therefore, these lakes can not be detected by conventional method such as Normalized Difference Water Index (NDWI), because the reflectance feature of shadowed glacial lake is different comparing to the ones which are located in the open flat area. The shadow causes two major problems: 1) glacial lakes which are covered by shadow completely result in underestimation of the number of glacial lakes; 2) glacial lakes which are partly identified are considered to undervalue the area of glacial lakes. The aim of this study is to develop a new model, named Detection of Shadowed Glacial Lakes (DSGL) model, to identify glacial lakes under the shadow environment by using Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) data in the Himalayas, Nepal. The DSGL model is based on integration of two different modifications of NDWI, namely NDWIs model and NDWI she model. NDWIs is defined as integration of the NDWI and slope analysis and used for detecting non-shadowed lake in the mountain area. The NDWIshe is proposed as a new methodology to overcome the weakness of NDWIs on identifying shadowed lakes in highly elevated mountainous area such as the Himalayas. The first step of the NDWIshe is to enhance the data from ASTER 1B using the histogram equalization (HE) method, and its outcome product is named ASTER he . We used the ASTER he for calculating the NDWI he and the NDWIshe . Integrated with terrain analysis using Digital Elevation Model (DEM) data, the NDWI she can be used to identify the shadowed glacial lakes in the Himalayas. NDWIs value of 0.41 is used to identify the glacier lake (NDWIs≥0.41), and 0.3 of NDWIshe is used to identify the shadowed glacier lake (NDWIshe≤0.3). The DSGL model was proved to be able to classify the glacial lakes more accurately, while the NDWI model had tendency to underestimate the presence of actual glacial lakes. Correct classification rate regarding the products from NDWI model and DSGL model were 57% and 99%, respectively. The results of this paper demonstrated that the DSGL model is promising to detect glacial lakes in the shadowed environment at high mountains. | CHEN Wenbo FUKUI Hiromichi DOKO Tomoko GU Xingfa | 2013 | Chinese Geographical Science2013，23，2： | 2 |
| 5 | A twin-channel difference model for cross-calibration of thermal infrared band显示文摘Based on the conduction and transformation of the thermal infrared radiative transfer equation of water target,a twinchannel difference model(DM) was proposed to improve the calibration precision by conquering the limitation that the atmospheric condition when image is acquiring cannot be truly obtained in the traditional radiometric simulation calibration method.The analysis of surface,atmosphere and top-of-atmosphere(TOA) radiative energy decomposition demonstrated that the apparent TOA radiance of the uncalibrated channel is the differential combination of two reference channels.The DM avoids impacts from atmospheric temperature and density.The only impact is from water vapor(WV) content.Based on the fitting error analysis of 742 mid-latitude atmospheric profiles(column WV content:0-5×10 3 atm cm) selected from TIGR database,the DM is insensitive to WV content.The maximum error is less than 0.2 K when the view zenith angels(VZAs) of reference channels and uncalibrated channel are less than 30.The error becomes 0.3 K when VZAs range from 30 to 40 and 0.6 K when VZAs are in 40-50.Because the uncertainty increases when VZAs are larger than 50,the best range of VZAs is 30-50.The vicarious calibration results at Lake Qinghai field indicated that the calibration precision of the DM cross-calibration by using MODIS bands 31 and 32 as reference channels to calibrate IRS band 08 is similar to that of vicarious calibration.Therefore,the DM is a reliable alternative tool for sensor on-orbit calibration and validation with high precision and frequency. | LI JiaGuo GU XingFa YU Tao LI XiaoYing GAO HaiLiang LIU Li XU Hui | 2012 | Science China(Technological Sciences)2012，55，7： | 2 |
| 6 | Modeling diurnal variation of ground thermal radiance images using energy balance model and endmember composing technique显示文摘Modeling and analyzing dynamic changes of land thermal radiance scenes play an important role in thermal remote sensing.In this paper,the diurnal variation of ground surface thermal scene is mainly discussed.Firstly,based on the land surface energy balance equation,the diurnal variation of land surface temperatures(LSTs) over bare land covers were simulated by an analytical thermal model with second harmonic terms,and the diurnal LST variation of vegetation canopy was simulated using the Cupid model.Secondly,normalized difference vegetation index(NDVI),normalized difference water index(NDWI),and ratio resident-area index(RRI) were used to evaluate the endmember abundance of four land cover types including vegetation,bare soil,impervious and water area,which were calculated from IKONOS visible and near infrared(VNIR) bands.Finally,the thermal radiance scenes at various times and view angles were modeled based on the linear-energy-mixing hypothesis.The results showed that the simulated daily LST variations for vegetated and bare surfaces are correlated with the measured values with a maximum standard deviation of 2.7°C,that land thermal radiant textures with high-resolution are restored from the linear-energy-mixing method,and that the information abundance of the scene are related to the distribution of land cover,the imaging time,and the view angle. | ZHAO LiMin GU XingFa YU Tao WAN Wei XIONG Pan XIE YanHua ZHANG Lun | 2012 | Science China(Technological Sciences)2012，55，11： | 2 |
| 7 | Water target based cross-calibration of CBERS-02 CCD camera with MODIS data显示文摘 | Junwu Tang Xingfa Gu Shengli Niu Chaofei Ma Xiangjun Min | 2005 | Science in China Series E Engineering & Materials Science2005，，2： | 1 |
| 8 | Relating soil surface moisture to reflectance 显示文摘 | Liu Weidong F Baret Gu Xingfa | 2002 | Remote sensing of the environment2002，81，23： | 1 |
| 9 | Initial research on the polarized reflectance of typical urban surface types measured by the Directional Polarimetric Camera显示文摘This paper retrieves the bidirectional polarization distribution functions (BPDFs) of the distinct urban cover in the Pearl River Delta (PRD) region employing the high spatial resolution of multi-angle polarized measurements made by the Directional Polarimetric Camera (DPC).The BPDF operational products of MICROPOL and POLDER measurements were used to validate the BPDF products of the DPC,with the results demonstrating that the BPDF product of the DPC measurements accurately expresses the surface polarized reflectance.The polarized reflectance of distinct surface types in the PRD region was studied using the DPC measurements.The results demonstrate that the polarized reflectances of different surface types differ and decrease as the normalized difference vegetation index increases.The polarized reflectance of a distinct surface type in the PRD region decreases with increasing scattering angle.The basic theory of investigating surface properties using multi-angle polarized measurements is proposed. | XIE DongHai GU XingFa CHENG TianHai YU Tao LI ZhengQiang CHEN XingFeng CHEN Hao GUO Jing | 2011 | Science China Earth Sciences2011，54，8： | 1 |
| 10 | Multi-parameters of Thermal Infrared Remote Sensing Anomalies of the Earthquake显示文摘Temporal and spatial anomalies associated with the Yushu earthquake, including the Outgoing Longwave Radiation( OLR), the Land Surface Temperature( LST) and surface temperature from the National Center for Environmental Prediction( NCEP) are studied using thermal infrared remote sensing data in this paper. All results confirmed the previous observations of thermal anomalies in the seismic region prior to this earthquake.Among the multi-parameter anomalies, the underground water temperature anomaly appeared first and lasted for the longest time; OLR anomaly,an infrared parameter which indicates the radiation characteristics of the land surface medium,was the first to be detected; LST anomalies appeared later than OLR. NCEP temperature indicates the average atmosphere temperature with a certain vertical thickness; therefore,it was the last detected anomaly. The anomalies of OLR and LST lasted for a similar time length and were all located in the south or southwest of the epicenter. | Lu Xian Meng Qingyan Gu Xingfa Zhang Xiaodong Xiong Pan Ma Weiyu Xie Tao | 2016 | Earthquake Research in China2016，30，4： | 1 |
| 11 | Relating soil surface moisture to reflectance显示文摘 | LIU WEIDONG BARET F GU XINGFA | 2002 | Remote Sensing of Environment2002，81，： | 1 |
| 12 | Relating soil surface moisture to reflectance 显示文摘 | Liu Weidong Baret F Gu Xingfa | 2002 | Remote Sensing of Environment2002，81，： | 1 |
| 13 | Relating soil surface moisture to reflectance显示文摘 | Liu Weidong F. Baret Gu Xingfa Tong Qingxi Zheng Lanfen Zhang Bing | 2002 | Remote Sensing of Environment2002，，2： | 1 |
| 14 | Method study and uncertainty analysis of calibration coefficients validation based on the Inner Mongolia test site显示文摘Calibration coefficients validation is the foundation for ascertaining the sensor performance and carrying out the quantitative application.Based on the analysis of the differences between the calibration and validation,two calibration coefficients validation methods were introduced in this paper.Taking the HJ-1A satellite CCD1 camera as an example,the uncertainties of calibration coefficients validation were analyzed.The calibration coefficients validation errors were simulated based on the measured data at an Inner Mongolia test site.The result showed that in the large view angle,the ground directional reflectance variation and the atmospheric path variation were the main error sources in calibration coefficients validation.The ground directional reflectance correction and atmospheric observation angle normalization should be carried out to improve the validation accuracy of calibration coefficients. | GAO HaiLiang GU XingFa YU Tao GONG Hui LI JiaGuo LI XiaoYing | 2013 | Science China Earth Sciences2013，56，9： | 1 |
| 15 | Relating soil surface moisture to reflectance显示文摘 | Liu Weidong Baret F Gu Xingfa | 2002 | Remote Sensing of Environment2002，81，： | 1 |
| 16 | The influence of rainfall on PR radar measurement of ocean surface wind speed and its calibration显示文摘Rain can significantly degrade the wind vector retrieval from Precipitation Radar(PR) by three mechanisms, namely, two-way rain attenuation, rain volume-backscattering, and ocean surface roughening from the rain splash effect. Here we first derive the radar equation for PR in rainy conditions. Then we use the rain attenuation model for Ku band, volume backscatter model for spherical raindrops and PR–TMI(TRMM Microwave Imager, TMI) matchup datasets from June to August in 2010 to solve the radar equation, and quantitatively analyze the influence of rainfall on PR radar measurement of ocean surface wind speed. Our results show that the significant effect of rain on radar signal is dominated by two-way rain attenuation and rain splash effect, and the effect of rain volume-backscattering is relatively the weakest, which can even be neglected in rain-weak conditions. Moreover, both the two-way rain attenuation and rain splash effect increase with the increasing of integration rain rate and incident angle. Last, we combine volume-backscattering effect and splash effect into a simple phenomenological model for rain calibration and select three typhoon cases from June to August in 2012 to verify the accuracy of this model. Before calibration, the mean difference and mean square error(MSE) between PR-observed ? 0 and wind-induced ? 0 are about 2.95 dB and 3.10 dB respectively. However, after calibration, the mean difference and MSE are reduced to 0.64 dB and 1.61 dB respectively. The model yields an accurate calibration for PR near-nadir normalized radar cross section(NRCS) in rainy conditions. | LIU Peng GU XingFa YU Tao LI Juan DONG Wen | 2014 | Science China Earth Sciences2014，57，10： | 0 |
| 17 | Satellite detection of IR precursors using bi-angular advanced along-track scanning radiometer data:a case study of Yushu earthquake显示文摘The paper has developed and proposed a synthesis analysis method based on the robust satellite data analysis technique(RST) to detect seismic anomalies within the bi-angular advanced along-track scanning radiometer(AATSR) gridded brightness temperature(BT)data based on spatial/temporal continuity analysis. The proposed methods have been applied to analyze the Yushu(Qinghai, China) earthquake occurred on 14 th April 2010,and a full AATSR data-set of 8 years data from March2003 to May 2010 with longitude from 91°E to 101°E and latitude from 28°N to 38°N has been analyzed. Combining with the tectonic explanation of spatial and temporal continuity of the abnormal phenomena, the analyzed results indicate that the infrared radiation anomalies detected by the AATSR BT data with nadir view appear and enhance gradually along with the development and occurring of the earthquake, especially along the Ganzi-Yushu fault, Nu River fault and Jiali-Chayu fault; more infrared anomalies along the earthquake fault zone(Lancangjiang fault and Ning Karma Monastery-Deqin fault) are detected using the proposed synthesis analysis method, which can also characterize the activity of seismic faults more precisely. | Pan Xiong Xuhui Shen Xingfa Gu Qingyan Meng Yaxin Bi Liming Zhao Yanhua Zhao Yan Li Jianting Dong | 2015 | Earthquake Science2015，28，1： | 0 |
| 18 | Characteristic difference analysis and transfer parameter determination for different satellites to detect NDVI values显示文摘Here we propose a new method of NDVI difference analysis and NDVI difference correction for multi-sensors to detect NDVI.This method integrate PROSPECT model,SAIL model and MODTRAN atmospheric radioactive transfer model to simulate the remote sensing signals of different satellites for both NDVI difference analysis and correction without using real satellite images.The effects of both the sensors' spectral responses and atmospheric condition are simulated,and the differences among NDVI values derived from thirty different satellites are analyzed quantitatively.Focusing on the conversions of NDVI values among different satellites,through linear regression analysis,we estimate the transfer parameters between any two different satellite NDVI values,and present the lookup tables of transfer parameters under the atmospheric conditions of three surface visibility range values (10,23 and 50 km).The proposed method is useful for NDVI applications and analyses for multi-sensors. | LI Li GU XingFa YE ZeTian YU Tao MENG QingYan WANG YuXi | 2012 | Science China Earth Sciences2012，55，5： | 0 |
| 19 | ANALYSIS OF SPECTRAL CHARACTERISTICS AMONG DIFFERENT SENSORS BY USE OF SIMULATED RS IMAGES显示文摘This research,by use of RS image_simulating method,simulated apparent reflectance images at sensor level and ground_reflectance images of SPOT_HRV,CBERS_CCD,Landsat_TM and NOAA14_AVHRR’s corresponding bands.These images were used to analyze sensor’s differences caused by spectral sensitivity and atmospheric impacts.The differences were analyzed on Normalized Difference Vegetation Index(NDVI).The results showed that the differences of sensors’ spectral characteristics cause changes of their NDVI and reflectance.When multiple sensors’ data are applied to digital analysis,the error should be taken into account.Atmospheric effect makes NDVI smaller,and atmospheric correction has the tendency of increasing NDVI values.The reflectance and their NDVIs of different sensors can be used to analyze the differences among sensor’s features.The spectral analysis method based on RS simulated images can provide a new way to design the spectral characteristics of new sensors. | YE Zetian GU Xingfa LIU Xianlin WANG Zhimin | 2000 | Geo-Spatial Information Science2000，3，2： | 0 |
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