最新刊期
卷 18 ， 期 2 ， 2014
- 摘要："Higher Resolution Global Land Cover Mapping"program requires global data from two base years（ 2000,2010） with30 m spatial resolution multispectral images for global land cover mapping. These data should undergo radiometric and geometric precision correction. The data mainly comprise Landsat TM / ETM + images supplemented by HJ-1A / B CCD. In total,more than20000 images require radiometric correction and more than 1000 HJ-1A / B CCD images require precise geometric correction. With such a large data set,automated processing is necessary. This paper presents a solution to key issues on the automatic geometric correction of HJ-1A / B CCD images and precision evaluation results. This paper also presents solutions to key issues on the automatic radiometric correction of Landsat TM / ETM + and HJ-1A / B CCD images and accuracy assessment results. Finally,this paper presents some suggestions for the processing of large data sets.关键词：Landsat TM /ETM +;HJ-1A /B CCD;radiometric correction;geometric precision correction
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发布时间：2021-06-10 - 摘要：Two optical satellites HJ-1A and HJ-1B play an important role in natural disaster monitoring and risk assessment,e nvironment monitoring,and other fields. However,the system geometric correction products of HJ-1 CCD have low geometric precision and need to be corrected. HJ-1 CCD images have a larger aspect angle,a wider swath width and a larger image size. F urthermore,local geometric distortions are too complex in one scene. Thus,the geometric correction is difficult. In this paper,a hierarchical approach to automatic registration between HJ-1 CCD images and Landsat TM images based on the combination of Forstner operator and template matching is proposed firstly. The approach can obtain a large number of Control Points（ CPs） with high precision and even distribution. These CPs are used to generate Delaunay TIN. Then,local distortions of HJ-1 images can be rectified with the Delaunay triangulated irregular network（ Delaunay TIN）. A geometric precise correction system is then implemented,thereby completing the automatic processing for global HJ-1 images. Experiments with six HJ-1 images demonstrate that the approach is efficient,accurate,and fully automatic.关键词：HJ-1 CCD image;geometric precise correction;hierarchical registration;Delaunay TIN;RANSAC
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发布时间：2021-06-10 - 摘要："Higher Resolution Global Land Cover Mapping"program requires the radiometric normalization of two sets of base-year（ 2000,2010） global coverage 30 m resolution remote sensing data. All data must be converted from Digital Number（ DN） v alues to surface reflectance. Landsat TM / ETM + and HJ-1A / B CCD data are used in this study. A number of these data are not suitable for absolute atmospheric correction. To ensure the global coverage of these data,we have designed an algorithm for automatic relative radiometric normalization and accuracy verification. By using overlapping areas of the adjacent data,the data are converted directly from DN values to surface reflectance by means of relative radiometric correction. The MODIS surface reflectance product（ MOD09GA） is used as reference data,and the relative consistency of the corresponding bands is measured. Image block processing and OpenMP acceleration technologies are used to improve the efficiency of the algorithm. Practical application shows that our algorithm can meet the projected radiometric normalization accuracy,speed,and automation requirements.关键词：relative radiometric normalization;pseudo-invariant features;multivariate alteration detection;Landsat TM /ETM +;HJ-1A/B CCD;MODIS MOD09GA
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发布时间：2021-06-10 - 摘要：Topographic correction reduces terrain effects and improves radiation quality,such enhancements are beneficial to the improvement of computer classification accuracy in mountains. This paper designed a topographic correction method specifically for the global land cover classification of Landsat TM / ETM + data. This method first smoothens the terrain slope angle and then performs a cosine correction based on the smoothed terrain. This method effectively removes radiation abnormalities in the results of Cosine correction（ COS） and other Lambertian-based methods. This method and several other common methods,such as C,SCS,and Minnaert corrections,were tested on six Landsat TM / ETM + data from different regions of the world with different land cover types. Visual and statistical analyses were conducted to assess the performance of these methods in terms of two aspects: overcorrection and homogeneity within a land cover class. Comparison results indicate that the smoothing step significantly reduces overcorrection. This simple and effective algorithm avoid complex atmospheric parameter estimations. Engineering requirements of t errain correction for global land cover classification are met.关键词：topographic correction;smoothed terrain;Landsat TM /ETM +;COS correction;Minnaert correction;gamma correction
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发布时间：2021-06-10 - 摘要：Regional and clear data sets on a specified date is difficult for Landsat 5 because of low temporal resolution（ 16 d）. In this study,we develop a spatial-temporal fusion algorithm based on semi-physical model-multiplicative modulation fusion algorithm and generate synthetic multi-temporal Landsat 5 TM / ETM + reflectance data with the help of multi-temporal MODIS r eflectance data. A regional scaled data set of surface reflectance with high spatial and temporal resolution is retrieved after image mosaicking.In this study,we generate three temporal Landsat 5 TM reflectance data that cover Jilin Province in China by utilizing Landsat 5 TM surface reflectance data,and the 500 m MOD09A1 reflectance products were collected from 2006 to 2011. Surface reflectance mosaic data that cover the study area were then derived. Primary analysis shows that the generated Landsat 5 TM r eflectance data have good agreement with the MOD09A1 reflectance data in spectral distribution features,and color distribution appears to be uniform（ no obvious color differences）.关键词：spatial-temporal fusion;semi-physical model;multiplicative modulation;Landsat TM /ETM +;MODIS;surface reflectance data sets
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发布时间：2021-06-10 - 摘要：Radiometric correction,which is often used as a preliminary step for remote sensing classification,is required in the e fficient extraction of land-cover information from remote sensing images,particularly in areas with rough terrain. The objective of this study is to examine the effect of different radiation correction methods of Landsat TM data on land-cover remote sensing classification. Three different radiometric correction methods（ ATCOR 3,FLAASH and Look-Up Table（ LUT）） were introduced,and the Maximum Likelihood Classifier（ MLC） and Support Vector Machines（ SVMs） were used for classifiers. The training samples were s elected from three corrected images based on geographical coordinates and classifier training to classify the three corrected images mutually. The results indicate the following.（ 1） The samples selected from the classification image for classifier training significantly improve classification accuracy compared with the samples selected from other images.（ 2） The classification results of the three radiometric correction images are different,whereas the results of the ATCOR3 and FLAASH methods are similar.（ 3）The effect of radiometric correction on the classification accuracy of each category is different: radiometric correction affects"Forest"significantly and other categories variably.关键词：radiation correction;Landsat TM;MLC;SVMs;land-cover classification;Accuracy assessment
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发布时间：2021-06-10 - 摘要：The leaf reflectance spectra of plants polluted with heavy metal copper exhibit abnormal behavior. This paper investigates the spectral changes in copper-polluted leaves using seven spectral signatures and the spectral angle method. Wheat and l ettuce were selected as the experimental subjects and were cultured in copper-polluted soil. Leaf spectra reflectance and scanning electron micrograph of ten copper treatment groups were measured in four regular periods. The reflectance spectra of the leaves were obtained using an ASD Field Spectrometer. Results showed that the irregular spectral changes of copper-polluted leaves d epend on crop growth stages and crop types. The spectral angle,a simple method of comparing the vector angle of the leaf spectra with the given threshold values,has been justified as an efficient method of describing the spectral differences between copper-p olluted leaves and healthy leaves. The method is very sensitive to light and the severity of copper pollution. Results also show that the leaf structural parameter（ N） of copper-polluted leaves is larger than that of healthy leaves. The linear relationship between N and the reflectance value of the red shoulder was fitted with a correlation coefficient of 0. 978. As a result,the deduced N from the leaf reflectance spectra may be used as an indicator to reflect the leaf structure distortion under copper pollution conditions. The significance of this study lies in its provision of data asbasis and theoretical support for the construction of a copper-polluted leaf reflectance spectral model.关键词：heavy metal pollution;leaf reflectance spectra;characteristic wavelength;spectral angle;PROSPECT model
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发布时间：2021-06-10 - 摘要：In this paper,we propose a new algorithm to realize rapid buffer analysis of vector data in three-dimensional digital earth using a Graphic Processor Unit（ GPU）. In this algorithm,a texture map with four channels is used as the container to transmit the vector data to a GPU with highly efficient parallel computing features. The distance between the vector point corresponding to each pixel in the target buffer texture and the original object is calculated in the GPU,and the buffer texture is obtained by r endering one frame before the boundaries of the buffer zone are finally extracted. Our proposed algorithm is also compared with two traditional CPU algorithms by processing data for selected rivers and lakes in China. The result shows that the proposed method has improved the computation efficiency by 11—20 times compared to the CPU raster algorithm and 9—16 times compared to the CPU vector algorithm. The proposed algorithm is simple to use and also can solve the self-intersection problem which is presented in conventional algorithms. With the growth of number of vertexes,the speed of buffer analysis realized with this new algorithm is significantly higher than with traditional ones.关键词：buffer analysis;GPU computing;Digital Earth;three-dimensional GIS;boundary extraction
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发布时间：2021-06-10 - 摘要：Terrestrial Laser Scanning（ TLS） has shown great potential in obtaining the structural parameters of individual trees in past decades. In this work,three-dimensional point cloud data generated from TLS were obtained for a homogeneous forest plot with20 Pinus bungeana（ Pinus bungeana Zucc） trees. Through the analysis of the vertical profile of the point cloud data of an individual tree,a voxel-based method was developed to estimate crown base height. Further,the tree crowns were delineated by calculating the convex hull of each horizontal sliced point cloud data at different heights. In addition,crown volume,crown width,tree height,and Diameter at Breast Height（ DBH） were estimated at the same time. The TLS-based estimation captured 97% variation of the manually measured clear bole height（ n = 20,Root Mean Square Error（ RMSE） = 0. 21 m,p = 0. 01）. The R2and RMSE of DBH provided the coefficient of R2was 0. 79 and 1. 07 cm（ n = 20）,respectively. Crown length,DBH,and crown width were selected to predict crown volume by the stepwise linear regression method,and statistical analysis showed that the linear regression m odel explained 96. 7% of the crown volume variance with an RMSE of 2. 64 m3（ n = 20,p = 0. 01）. The method developed in this i nvestigation accurately estimated crown base height and crown geometry and can thus facilitate the application of TLS in precision forestry.关键词：terrestrial laser scanning;voxel;convex hull;crown base height;crown outline;crown volume
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发布时间：2021-06-10 - 摘要：This paper analyzes and discusses the main problems of line detection and extraction by traditional Hough transform in detail. Thus,it proposes an algorithm of straight line extraction by Hough transform combining edge grouping. This algorithm first adopts an edge tracking based on eight-neighborhood to group the detected edge points by Canny operator. It then separately p erforms the Hough transform to each edge group obtained by grouping,and individually determines the origin of the Hough transform and the range of parameter. This algorithm uses the iterative vote scheme to determine the single peak and the corresponding points to be deleted. The experimental results prove that the proposed algorithm is simple in principle and can effectively solve problems in the traditional Hough transform,such as low precision and complex computation. The proposed algorithm has robustness,can process different content images,and is suitable for parallel processing.关键词：straight line extraction;Hough transform;edge grouping;Edge tracking
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发布时间：2021-06-10 - 摘要：Quality control and quality assessment are important tasks in developing quantitative remote sensing products. Product quality can provide detailed information for users. However,quality control and assessment of remote sensing products may be d ifficult to achieve,particularly for products with complicated algorithms that require the verification and assessment of numerous inputs,which is time-consuming. This paper describes a proposed method of quality control and quality assessment for Photosynthetically Active Radiation（ PAR） products. Within the design of the overall technology framework,the detailed input data,the quality control system for the products,and the method of quality control and quality assessment are clearly demonstrated. Multisource remote sensing data and other geographical data for PAR estimates can result in numerous uncertainties. Thus,the quality control scheme was established using algorithm uncertainty analysis,quality system design and multiple levels of the products,and each possible uncertainty / error was recorded in the overall assessment of the products. The quality assessment method is briefly d escribed using the ground measured data and quality designation of products.关键词：quantitative remote sensing products;quality control;quality assessment;Photosynthetically Active Radiation（PAR）
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发布时间：2021-06-10 - 摘要：To investigate the characteristics of rainstorm clouds to local precipitation,we analyzed 19 typical cases of rainstorm process in the Eastern Qinghai-Tibetan Plateau from four hours before precipitation to two hours after based on the cloud-top t emperature data of FY-2 infrared channels. Two patterns were found,and the first was the trend of temperature at the 7 × 7 pixels region centered at automatic meteorological stations,and the second was the analysis of convection parameters through identification and tracking convective clouds. In addition,the characteristics of radar echo of rainstorm clouds were also analyzed. In this p aper,the maximum temperature gradient on cloud top is represented as Gmax,the maximum amplitude of Gmaxwithin the half-hour is expressed in ΔGmax,and the minimum temperature on cloud top is denoted by Tmin. We found that the variation trend of cloud-top temperature and temperature gradient at infrared channels were consistent,and the cloud-top temperature showed a decrease before increase while the temperature gradient was the opposite in precipitation stage. One or two peaks of Gmaxand ΔGmaxhappened about0 to 11 hours earlier than the heavy precipitation. The multiple regression equation for forecasting precipitation grade was constructed by Tminand Gmax. It showed that the model can well simulate the tendency of hourly precipitation and can also predict heavy rain,and the error of hourly precipitation is within one grade of precipitation. The R2of regression improved from 0. 23 to 0. 54,and the precipitation peak can be better modeled after considering the contribution of Gmaxpeak. The new algorithm of clouds identification and tracking is more simple and effective than other methods. All rainstorm cloud clusters over eastern Plateau are at mid-β to mid-α scale,and their height of water vapor columns are deep but the intensity are weaker than that of the lower altitudes. The p recipitation will happen within several hours when the minimum distance between the position of clouds extremum and the meteorological station is less than 15 pixels. The rainstorm clouds have the characteristics of heavy precipitation super cell storm in r adar echo,and the extremes of Tminand Gmaxcorrespond with the extremes of vertical integrated liquid water content,echo-top height and its gradient. These results are important for identification and tracking strong convective cloud clusters and short-time precipitation forecasting in eastern Qinghai-Tibetan Plateau.关键词：infrared channels;local rainstorms cloud clusters;identification and tracking;short-time precipitation forecasting
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发布时间：2021-06-10 - 摘要：This study uses the Standard Precipitation Index（ SPI） to compare the responses of eight MODIS-based spectral indices to typical drought events,including NDVI,NDWI,VARI,EVI,NDIIB6,NDIIB7,D1640,and SR,from 2000 to 2012 in southwest China,Containing the provinces of Sichuan,Chongqing,Yunnan,and Guizhou. The results show that:（ 1） The SPI index derived from precipitation data could reflect the drought conditions around the station,and the three-month and six-month SPIs（ SPI3/6） perform better than the other time-scale SPIs;（ 2） Anomalies of all eight MODIS-based spectral indices,except for D1640,show significant correlation with SPI3 at a confidence level of 95% and can thus be used to reveal the drought conditions in southwest China to some degree,whereas anomalies of NDIIB7,VARI,EVI,and NDIIB6 have higher r values with SPI3（ r > 0.3） than others;（ 3） The anomalies of NDIIB7 have the highest r value with SPI3 and are used to analyze the spatiotemporal development and r ecovery of the long-term extreme drought event that occurred in Yungui Plateau during 2009 to 2010.关键词：drought;MODIS spectral index;SPI;Southwest China
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发布时间：2021-06-10 - 摘要：Large-scale land cover datasets comprise an important foundation of the research on land surface processes,ecosystem assessment,and environmental modeling. The evaluation of existing land cover datasets provides a guide to dataset use and new dataset production. Five kinds of global land cover datasets（ IGBP DISCover,UMD,GLC2000,MOD12 Q1,and GlobCover2005） over China and adjacent regions are evaluated in this paper. First,the categories of five land cover datasets are translated into the International Geosphere-Biosphere Programme-IGBP scheme based on the correlation coefficients of the corresponding classes,which is computed according to the class definition in each land cover dataset. Second,the spatial agreements of the five land c over datasets are analyzed using visual comparison and per-pixel comparison. Finally,the classification accuracy of the five land cover datasets is evaluated based on validation samples collected through Google Earth high-resolution satellite images. The results show large areas of disagreement among the five land cover datasets,and the overall consistency among them is low. GLC2000 has the highest overall accuracy and Kappa coefficient,whereas GlobCover 2005 has the lowest overall accuracy and Kappa coefficient.关键词：Land cover datasets;comparison analysis;Accuracy assessment;Google Earth
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发布时间：2021-06-10 - 摘要：The Soft and Hard Land Use /Cover Change Detection（ SHLUCD） was proposed to express the variation of crop phenology effectively,which will help identifying the target crop both in discretely and continuously changed regions（ discrete region is in an area that was totally changed into crop and non-crop region; the continuously changed region is in a transitional area where part of the target crop is changed into crop）. The method was applied in a sub-region of Beijing. Two HJ-1 CCD images that were utilized by Hard Land Use / Cover Change Detection（ HLUCD）,Soft Land Use / Cover Change Detection（ SLUCD）,and SHLUCD to extract winter wheat area in the study area; the images were acquired on October 6,2011（ T1） and April 16,2012（ T2） represent the period of sowing and jointing,respectively. The results showed that the crop distribution derived from the SHLUCD can get a higher accuracy than that from HLUCD and SLUCD. The crop distribution derived from the SHLUCD also performs better in scale evaluation than that derived from other methods; the former has lower RMSEs and bias and higher R2value. The RMSEs of SHLUCD,HLUCD,and SLUCD are in the ranges of 0. 14 to 0. 07,0. 15 to 0. 07,and 0. 16 to 0. 08,respectively; the biases of SHLUCD,HLUCD,and SLUCD are approximately- 0. 0008,- 0. 007,and 0. 014,respectively; the R2values of SHLUCD,HLUCD,and SLUCD are in the ranges of 0. 68 to 0. 86,0. 62 to 0. 86,and 0. 60 to 0. 86,respectively. Accuracy assessment was also applied in abruptly changed area,continuously changed area and non-crop area respectively. It shows that the accuracy assessment results of SHLUCD are similar to that from the best method in all three regions. Therefore,our method is more flexible and suitable in crop mapping. The winter wheat mapping in discrete and continuously changed regions can be identified by the status of land use / cover change and land change scope through SHLUCD,respectively. Moreover,SHLUCD provides a new way for crop distribution mapping based on change detection.关键词：winter wheat identification;change detection technique;Extended Support Vector Machine（ESVM）;phenology
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发布时间：2021-06-10
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