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RESEARCH ON THE LOCAL CORRECTION MODEL OF ATMOSPHERIC DRY DELAY IN GPS REMOTE SENSING WATER VAPOR 被引量:3
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作者 谷晓平 王长耀 +1 位作者 王汶 蒋国华 《Journal of Tropical Meteorology》 SCIE 2005年第1期78-85,共8页
The precision of atmospheric dry delay model is closely correlated with the accuracy of GPS water vapor in the process of GPS (Global Position System) remote sensing. Radiosonde data (from 1996 to 2001) at Qingyuan ar... The precision of atmospheric dry delay model is closely correlated with the accuracy of GPS water vapor in the process of GPS (Global Position System) remote sensing. Radiosonde data (from 1996 to 2001) at Qingyuan are used to calculate the exact values of the atmospheric dry delay. Base on these calculations and the surface meteorological parameters, the local year and month correction models of dry delay at the zenith angle of 0° are established by statistical methods. The analysis result shows that the local model works better and is slight more sensitive to altitude angle than universal models and that it is not necessary to build models for each month due to the slight difference between year model and month model. Furthermore, when the altitude angle is less than 75°, the difference between curve path and straight path increases rapidly with altitude angle’s decrease. 展开更多
关键词 GPS remote sensing water vapor atmospheric dry delay local correlation model
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Spatial scaling of net primary productivity model based on remote sensing 被引量:5
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作者 WANG Liwen WEI Yaxing NIU Zheng 《遥感学报》 EI CSCD 北大核心 2010年第6期1074-1081,共8页
Spatial scaling for net primary productivity (NPP) refers to the transferring process of establishing quantitative correlation between simulated NPP derived from data at different spatial resolutions. How to transfe... Spatial scaling for net primary productivity (NPP) refers to the transferring process of establishing quantitative correlation between simulated NPP derived from data at different spatial resolutions. How to transfer NPP at one scale by the algorithm with smaller error to at another is the urgent problem. Nonlinearity and effects from land cover type are two main problems in NPP scaling. In this paper, the contextural approach based on mixed pixels and support vector machine (SVM) algorithm are used to make the scaling model from the fine resolution (TM) to the coarse resolution (MODIS). Spatial scaling from NPP retrieved from fine resolution data to NPP derived from coarse resolution images is performed, and the correction of scale effect to NPP retrieved from coarse resolution data of MODIS is accomplished. The result shows that the correlation between Rj_coereted of the correction factor for scale effect and 1-Fmiddle dessity grassland estimated by SVM regression model is higher (R2=0.81). Before the correction for scale effect, the correlation between NPPMODIS and NPPTM is lower (R2=0.69; RMSE=3.47), while the correlation between NPPTM and corrected NPPMODIS_corrected is higher (R2=0.84; RMSE= 1.87). Therefore, NPP corrected for scale effect has been greatly improved in both correlation and error. 展开更多
关键词 net PRIMARY productivity light use efficiency model REMOTE sensing scaling support VECTOR machine
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Spatial and temporal variations of vegetation in Qinghai Province based on satellite data 被引量:9
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作者 WANG Liwen WEI Yaxing NIU Zheng 《Journal of Geographical Sciences》 SCIE CSCD 2008年第1期73-84,共12页
This paper used five years (2001-2006) time series of MODIS NDVI images with a 1-km spatial resolution to produce a land cover map of Qinghai Province in China. A classification approach for different land cover typ... This paper used five years (2001-2006) time series of MODIS NDVI images with a 1-km spatial resolution to produce a land cover map of Qinghai Province in China. A classification approach for different land cover types with special emphasis on vegetation, especially on sparse vegetation, was developed which synthesized Decision Tree Classification, Supervised Classification and Unsupervised Classification. The spatial distribution and dynamic change of vegetation cover in Qinghai from 2001 to 2006 were analyzed based on the land cover classification map and five grade elevation belts derived from Qinghai DEM. The result shows that vegetation cover in Qinghai in recent five years has been some improved and the area of vegetation was increased from 370,047 km^2 in 2001 to 374,576 km^2 in 2006. Meanwhile, vegetation cover ratio was increased by 0.63%. Vegetation cover ratio in high mountain belt is the largest (67.92%) among the five grade elevation belts in Qinghai Province. The second largest vegetation cover ratio is in middle mountain belt (61.80%). Next, in the order of the decreasing vegetation cover ratio, the remaining grades are extreme high mountain belt (38.98%), low mountain belt (25.55%) and flat region belt (15.46%). The area of middle density grassland in high mountain belt is the biggest (94,003 km^2), and vegetation cover ratio of dense grassland in middle mountain belt is the highest (32.62%), and the increased area of dense grassland in high mountain belt is the greatest (1280 km^2). In recent five years the conversion from sparse grass to middle density grass in high mountain belt has been the largest vegetation cover variation and the converted area is 15931 km^2. 展开更多
关键词 QINGHAI VEGETATION MODIS NDVI DEM spatial distribution
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Comparison of Different LiDAR and Hypespectral Data Fusion Strategies Using SVM and ABNet
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作者 Pengyu Hao Zheng Niu 《遥感科学(中英文版)》 2013年第3期41-46,共6页
关键词 融合策略 SVM 激光雷达 灵敏度测试 高光谱数据 分层分类 分类算法 LIDAR
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Retrieval of urban slow deformation using the multi-baseline DInSAR technique 被引量:2
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作者 WU mao ZHANG Hong +2 位作者 WANG Chao TANG YiXian WU HongAn 《Chinese Science Bulletin》 SCIE EI CAS 2008年第23期3705-3714,共10页
The investigation of slow displacement in urban areas using the multi-baseline DInSAR technique has been a hot research topic in the field of DInSAR. The basic flow of this technique includes several steps such as the... The investigation of slow displacement in urban areas using the multi-baseline DInSAR technique has been a hot research topic in the field of DInSAR. The basic flow of this technique includes several steps such as the combination of interferometric image pairs, generation of differential interferograms, selection of high coherent points, generation of the Delaunay triangular network, calculation and integration of increments in network, unwrapping and calibration of the residual phase, and the estimation of both atmospheric and nonlinear displacement phase. Among these steps, the calculation of increments is the key to retrieve linear displacement, while unwrapping and calibration of the residual phase are the keys to retrieve nonlinear displacement. In order to improve the performance of these two steps, this paper proposes a modified model coherence function for increments estimation, and a triangular "circle" algorithm to deal with phase unwrapping and calibration. Based on the above algorithms, the subsidence of Suzhou City is investigated using 24 ERS scenes from February 1993 to December 2000. The results show that the linear subsidence velocity of the most urban area is about -20 to -30 mm/a during the time, with a yearly decrease in velocity. The displacement seems to be stable after 2000. Leveling data validate our results and demonstrate the reliability of the algorithm. 展开更多
关键词 基线 DINSAR 地表面变形 遥感技术
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Mapping Lunar Olivine Using Clementine Spectral Indices and Chemical Composition Parameters 被引量:2
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作者 YUE Zongyu XIE Hongjie +1 位作者 DI Kaichang OUYANG Ziyuan 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2012年第1期65-72,共8页
Olivine exposures at the central peak of Copernicus crater of the Earth's Moon have been confirmed by telescope observations and Clementine spectra data. Using these exposures as training sites, this study used a met... Olivine exposures at the central peak of Copernicus crater of the Earth's Moon have been confirmed by telescope observations and Clementine spectra data. Using these exposures as training sites, this study used a method of combining two spectral indices (950 nm/750 nm and 2000 nm/1500 nm), one maturity index (Is/FeO), and four chemical content indices (FeO, Mg, Al, Ca), through a decision tree classifier, to map olivine-rich units on the west lunar surface based on mosaicked Clementine image (500 m pixel size). Most classified olivine exposures are found inside craters or on their rays, suggesting that olivine exposures are directly associated with the impact processes. The results have been validated in several selected sites, though further validations with data from the newest missions are strongly needed. 展开更多
关键词 CLEMENTINE OLIVINE Copernicus crater
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Significant discrepancies of land surface daily net radiation among ten remotely sensed and reanalysis products 被引量:1
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作者 Xiuwan Yin Bo Jiang +11 位作者 Shunlin Liang Shaopeng Li Xiang Zhao Qian Wang Jianglei Xu Jiakun Han Hui Liang Xiaotong Zhang Qiang Liu Yunjun Yao Kun Jia Xianhong Xie 《International Journal of Digital Earth》 SCIE EI 2023年第1期3725-3752,共28页
Land surface all-wave net radiation(R_(n))is crucial in determining Earth’s climate by contributing to the surface radiation budget.This study evaluated seven satellite and three reanalysis long-term land surface R_(... Land surface all-wave net radiation(R_(n))is crucial in determining Earth’s climate by contributing to the surface radiation budget.This study evaluated seven satellite and three reanalysis long-term land surface R_(n)products under different spatial scales,spatial and temporal variations,and different conditions.The results showed that during 2000-2018,Global Land Surface Satellite Product(GLASS)-Moderate Resolution Imaging Spectroradiometer(MODIS)performed the best(RMSE=25.54 Wm^(-2),bias=-1.26 Wm^(-2)),followed by ERA5(the fifth-generation of European Centre for Medium-Range Weather Forecast Reanalysis)(RMSE=32.17 Wm^(-2),bias=-4.88 Wm^(-2))and GLASS-AVHRR(Advanced Very-High-Resolution Radiometer)(RMSE=33.10 Wm^(-2),bias=4.03 Wm^(-2)).During 1983-2018,GLASS-AVHRR and ERA5 ranked top and performed similarly,with RMSE values of 31.70 and 33.08 Wm^(-2)and biases of-4.56 and 3.48 Wm^(-2),respectively.The averaged multi-annual mean R_(n)over the global land surface of satellite products was higher than that of reanalysis products by about 10~30 Wm^(-2).These products differed remarkably in long-term trends variations,particularly pre-2000,but no significant trends were observed.Discrepancies were more frequent in satellite data,while reanalysis products showed smoother variations.Large discrepancies were found in regions with high latitudes,reflectance,and elevation which could be attributed to input radiative components,meteorological variables(e.g.,cloud properties,aerosol optical thickness),and applicability of the algorithms used.While further research is needed for detailed insights. 展开更多
关键词 All-wave net radiation remote sensing REANALYSIS evaluation spatio-temporal variation product
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Evaluation of nine machine learning methods for estimating daily land surface radiation budget from MODIS satellite data
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作者 Shaopeng Li Bo Jiang +10 位作者 Shunlin Liang Jianghai Peng Hui Liang Jiakun Han Xiuwan Yin Yunjun Yao Xiaotong Zhang Jie Cheng Xiang Zhao Qiang Liu Kun Jia 《International Journal of Digital Earth》 SCIE EI 2022年第1期1784-1816,共33页
The all-wave net radiation(Rn)at the land surface represents surface radiation budget and plays an important role in the Earth's energy and water cycles.Many studies have been conducted to estimate from satellite ... The all-wave net radiation(Rn)at the land surface represents surface radiation budget and plays an important role in the Earth's energy and water cycles.Many studies have been conducted to estimate from satellite top-of-atmosphere(TOA)data using various methods,particularly the application of machine learning(ML)and deep learning(DL).However,few studies have been conducted to provide a comprehensive evaluation about various ML and DL methods in retrieving.Based on extensive in situ measurements distributed at mid-low latitudes,the corresponding Moderate Resolution Imaging Spectroradiometer(MODIS)TOA observations,and the daily from the fifth generation of European Centre for Medium-Range Weather Forecasts Reanalysis 5(ERA5)used as a priori knowledge,this study assessed nine models for daily estimation,including six classic ML methods(random forest-RF,adaptive boosting-Adaboost,extreme gradient boosting-XGBoost,multilayer perceptron-MLP,radial basis function neural network-RBF,and support vector machine-SVM)and three DL methods(multilayer perceptron neural network with stacked autoencoders-SAE,deep belief network-DBN and residual neural network-ResNet).The validation results showed that the three DL methods were generally better than the six ML methods except XGBoost,although they all performed poorly in certain conditions such as winter days,rugged terrain,and high elevation.ResNet had the most robust performance across different land cover types,elevations,seasons,and latitude zones,but it has disadvantages in practice because of its highly configurable implementation environment and low computational efficiency.The estimated daily values from all nine models were more accurate than the corresponding Global LAnd Surface Satellite(GLASS)product. 展开更多
关键词 Net radiation energy balance mid-low latitude model comparison machine learning deep learning MODIS ERA5
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A long-term Global LAnd Surface Satellite(GLASS)data-set for environmental studies 被引量:34
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作者 Shunlin Liang Xiang Zhao +13 位作者 Suhong Liu Wenping Yuan Xiao Cheng Zhiqiang Xiao Xiaotong Zhang Qiang Liu Jie Cheng Hairong Tang Yonghua Qu Yancheng Bo Ying Qu Huazhong Ren Kai Yu John Townshend 《International Journal of Digital Earth》 SCIE EI 2013年第S01期5-33,共29页
Recently,five Global LAnd Surface Satellite(GLASS)products have been released:leaf area index(LAI),shortwave broadband albedo,longwave broadband emissivity,incident short radiation,and photosynthetically active radiat... Recently,five Global LAnd Surface Satellite(GLASS)products have been released:leaf area index(LAI),shortwave broadband albedo,longwave broadband emissivity,incident short radiation,and photosynthetically active radiation(PAR).The first three products cover the years 19822012(LAI)and 19812010(albedo and emissivity)at 15 km and 8-day resolutions,and the last two radiation products span the period 20082010 at 5 km and 3-h resolutions.These products have been evaluated and validated,and the preliminary results indicate that they are of higher quality and accuracy than the existing products.In particular,the first three products have much longer time series,and are therefore highly suitable for various environmental studies.This paper outlines the algorithms,product characteristics,preliminary validation results,potential applications and some examples of initial analysis of these products. 展开更多
关键词 earth observation global environmental change remote sensing
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Estimating daily surface downward shortwave radiation over rugged terrain without bright surface at 30 m on clear-sky days using CERES data
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作者 Hui Liang Bo Jiang +3 位作者 Jianghai Peng Shaopeng Li Jiakun Han Xiuwan Yin 《International Journal of Digital Earth》 2023年第2期4317-4345,共29页
In this study,the authors propose a model,called the Daily Downward Shortwave Radiation Random Forest Model over Rugged Terrain(DSRMT),to accurately calculate the downward shortwave radiation over a terrain without br... In this study,the authors propose a model,called the Daily Downward Shortwave Radiation Random Forest Model over Rugged Terrain(DSRMT),to accurately calculate the downward shortwave radiation over a terrain without bright surface on clear days at a daily scale(DSRdaily−rugged).It was built by using the random forest method based on the comprehensive samples from CERES4_SYN1deg_Ed4A within 17 typical mountainous regions.DSRMT could directly estimate DSRdaily-rugged from the instantaneous direct and diffuse solar radiation on a flat surface during 10:30–14:30hrs on each day by comparing with the terrain factors from a digital elevation model,broadband albedo from the Global Land Surface Satellite,and ancillary information.The in-situ validation results showed that it generally delivered superior performance in estimating DSRdailyrugged at any time during 10:30–14:30hrs,especially at noon,yielding a validated root mean-squared error(RMSE)of 24.90–29.22 Wm−2 and mean absolute error(MAE)of 19.16–22.94 Wm−2,and the average weighted DSRdaily-rugged were usually more accurate with the RMSE and MAE of 21.63 and 17.14 Wm−2.Overall,DSRMT was found to deliver satisfactory performance because of its high accuracy,robustness,ease of implementation,and efficiency,so it has the strong potential to be widely used in practice. 展开更多
关键词 Daily downward shortwave radiation rugged terrain estimation modeling DSRMT CERES4 remote sensing
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Recent progress on evaluating and analysing surface radiation and energy budget datasets
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作者 Bo Jiang Xiaotong Zhang +1 位作者 Dongdong Wang Shunlin Liang 《International Journal of Digital Earth》 2023年第2期4929-4933,共5页
Although the surface energy budget is essential to determine Earth’s climate,site measurements of various radiative components are still too scarce to properly characterize their spatial and temporal variations.This ... Although the surface energy budget is essential to determine Earth’s climate,site measurements of various radiative components are still too scarce to properly characterize their spatial and temporal variations.This has led to the development of a growing number of surface radiation products,mainly including remotely sensed data,model reanalysis data,and simulations using General Circulation Models(GCMs).This collection of papers introduces new techniques,including the use of machine learning methods for radiation estimation,and evaluates and compares various radiation products,as well as their spatio-temporal variations.These studies show large discrepancies among various products across nearly all radiative parameters in either accuracy or spatio-temporal variations.However,remotely sensed radiation products perform relatively better than others.Despite this,there is an urgent need for further efforts to address these discrepancies and improve the accuracy of these estimates.Even though the major radiative parameters including downward shortwave radiation,net longwave radiation,and albedo,from most products show insignificant long-term variation trends on a global scale,only specific regions,such as the Yunnan-Kweichow Plateau(YKP)and regions with permafrost(i.e.Qinghai-Tibet Plateau and Arctic)and glaciers(i.e.Altai Mountains)exhibit remarkable trends. 展开更多
关键词 Surface radiation energy budget ESTIMATION EVALUATION spatio-temporal variation
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