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天气雷达反射率数据方位分辨率提高 被引量:3
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作者 李学华 何建新 何子述 《计算机工程与应用》 CSCD 北大核心 2011年第8期18-20,24,共4页
天气雷达反射率数据方位分辨率的提高,对中小尺度强对流天气过程的精细探测有重要的意义。以雷达气象积分方程为基础,通过对天气雷达反射率方位数据的过采样,建立雷达测量的低分辨反射率数据与真实气象目标高分辨率数据之间的矩阵方程,... 天气雷达反射率数据方位分辨率的提高,对中小尺度强对流天气过程的精细探测有重要的意义。以雷达气象积分方程为基础,通过对天气雷达反射率方位数据的过采样,建立雷达测量的低分辨反射率数据与真实气象目标高分辨率数据之间的矩阵方程,提出使用截断奇异值分解算法优化超分辨反演方程逆求解及改善解稳定性。实验结果验证,该方法对反射率数据方位分辨率的提高是行之有效的。 展开更多
关键词 天气雷达 反射率数据 超分辨 截断奇异值分解
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基于L1正则化的MODIS地表反射率数据时域重建方法
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作者 汪宇浩 沈焕锋 李志伟 《遥感技术与应用》 CSCD 北大核心 2024年第3期603-611,共9页
MODIS地表反射率数据被广泛应用于陆地表面的动态监测,但云覆盖等因素的影响使得数据中存在时空缝隙,从而影响了数据可用性。对此,提出一种基于L1正则化的时域重建方法,能有效修复MODIS地表反射率数据中的缺失,实现高精度的长时序数据... MODIS地表反射率数据被广泛应用于陆地表面的动态监测,但云覆盖等因素的影响使得数据中存在时空缝隙,从而影响了数据可用性。对此,提出一种基于L1正则化的时域重建方法,能有效修复MODIS地表反射率数据中的缺失,实现高精度的长时序数据重建。该方法首先识别时序数据中因自然因素及系统因素产生的噪声,然后基于噪声检测对信息缺失区域进行年际预填补,在此基础上引入对突变噪声更为稳健的L1正则化模型,并结合噪声标记构建时域重建变分模型,还原地表的时序变化趋势。实验结果表明:相比于SG滤波、HP滤波、L1滤波、谐波分析方法,在不同百分比10%、25%、50%、75%的像元缺失情况下,该方法都取得了最高的重建精度;在不同地表场景下,该方法也取得了更好的重建结果。因此,该方法在时序曲线重建和空间细节修复上都更具有优势,表现出较高的实用价值。 展开更多
关键词 时序数据重建 MODIS地表反射率数据 L1正则化 变分模型
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2017-2021年海南省GF-2地表反射率产品数据集
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作者 阎跃观 梁虎军 +4 位作者 张浩 张连翀 张宏伟 崔珍珍 陈善静 《中国科学数据(中英文网络版)》 CSCD 2022年第4期79-87,共9页
GF-2数据具有空间分辨率高、几何定位精度高等特点,单景影像观测幅宽可达45公里,在农业、林业等领域均具有广泛的用途。本数据集收集2017-2021年592景海南省全岛高分二号数据(GF-2 PMS)影像数据,通过可见光近红外迭代算法对数据进行大... GF-2数据具有空间分辨率高、几何定位精度高等特点,单景影像观测幅宽可达45公里,在农业、林业等领域均具有广泛的用途。本数据集收集2017-2021年592景海南省全岛高分二号数据(GF-2 PMS)影像数据,通过可见光近红外迭代算法对数据进行大气校正,完成了2017-2021年海南省GF-2地表反射率数据的生产。并通过SONET(Sun-sky radiometer Observation NETwork)三亚站点收集的气溶胶数据,生成用于验证反演算法产品的参考地表反射率数据。结果显示,GF-2的地表反射率数据与地基实测反射率的准确度、精确度、实际统计偏差统计值检验均在标准参考线之下,本数据集具有较高的精度,可以为海南省生态监测提供了技术支撑。 展开更多
关键词 地表反射率数据 高分二号 可见光近红外迭代算法 SONET数据
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地表反射率遥感数据支持的火烧迹地面积提取
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作者 牛方天 孙林 +1 位作者 于会泳 马超 《地球信息科学学报》 EI CSCD 北大核心 2023年第9期1855-1868,共14页
生物质燃烧排放大量烟雾和温室气体对于全球气候变化有显著影响,而准确及时地提取火烧迹地面积对于火灾补救、植被恢复、估算大气排放至关重要。中分辨率成像光谱仪MODIS较高的时间分辨率可以快速获取全球每日的火烧迹地产品,但对于小... 生物质燃烧排放大量烟雾和温室气体对于全球气候变化有显著影响,而准确及时地提取火烧迹地面积对于火灾补救、植被恢复、估算大气排放至关重要。中分辨率成像光谱仪MODIS较高的时间分辨率可以快速获取全球每日的火烧迹地产品,但对于小型和破碎度高的火烧迹地的遗漏率比较高。据此,本研究融合MODIS与Landsat-8 OLI(Operational Land Imager陆地成像仪)的时空优势,提出了基于地表反射率数据集支持的火烧面积提取算法。首先,使用MODIS地表反射率产品MOD09GA构建燃烧日期前后在红、绿、蓝、近红外和短波红外的先验地表反射率数据集。然后,采用自适应遥感图像时空融合算法(Spatial and Temporal Adaptive Reflectance Fusion Model,STARFM)以及线性拟合的方法对MODIS与Landsat-8地表反射率数据进行空间和光谱一致化处理。最后,运用自动阈值的方法厘定火烧区域的最佳阈值。此外,通过选取4个不同的燃烧规模样地/样区验证了该算法的火烧迹地面积提取准确率在75%以上。本研究将MODIS的高时间分辨率和Landsat-8的高空间分辨率的优势结合,既解决了单独使用MODIS对小型、破碎度高的火烧迹地提取不足的问题,也验证了基于地表反射率数据集的算法对于火烧迹地实时提取能力。 展开更多
关键词 生物质燃烧 火烧迹地 先验地表反射率数据 光谱一致化 MODIS Landsat-8 OLI
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地表反射率产品支持的GF-1PMS气溶胶光学厚度反演及大气校正 被引量:19
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作者 孙林 于会泳 +3 位作者 傅俏燕 王健 田信鹏 米雪婷 《遥感学报》 EI CSCD 北大核心 2016年第2期216-228,共13页
GF-1卫星PMS(GF-1 PMS)数据具有高空间分辨率、短重访周期的特点,可以在地表类型识别、参数提取中发挥重要作用。但由于缺少2.1μm附近的短波红外波段,使得气溶胶反演时地表反射率的精确确定非常困难,从而导致其高精度大气校正难以开展... GF-1卫星PMS(GF-1 PMS)数据具有高空间分辨率、短重访周期的特点,可以在地表类型识别、参数提取中发挥重要作用。但由于缺少2.1μm附近的短波红外波段,使得气溶胶反演时地表反射率的精确确定非常困难,从而导致其高精度大气校正难以开展,限制了该数据的应用。本文提出了一种地表反射率数据支持的气溶胶反演方法,用于GF-1PMS数据的大气校正。其基本思想是:使用现有的地表反射率数据集为GF-1PMS数据提供地表反射率,用于确定GF-1PMS图像中浓密植被像元(DDV)的分布,基于确定的浓密植被像元反演气溶胶光学厚度(AOD),并用于大气校正。这里使用的地表反射率数据集为合成的无云MODIS地表反射率产品,对GF-1PMS数据做了空间尺度的转换。为降低两类数据配准误差对地表反射率确定的影响,提出了使用区域NDVI分布百分比匹配的方法,回避了像元的直接匹配,为GF-1PMS数据提供DDV的空间分布。为验证该方法的有效性,利用北京、太湖两个AERONET站点观测的气溶胶光学厚度对气溶胶反演结果进行精度验证,结果表明,气溶胶反演算法精度较高,稳定性较强。AOD反演结果应用于北京和敦煌地区的GF-1PMS数据大气校正,获得的地表反射率与地面实测的地表反射率的误差低于0.015,且大气校正后影像对比度明显提高。 展开更多
关键词 GF-1 PMS 地表反射率数据 气溶胶光学厚度 大气校正
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Analysis of Physical Quantities and Radar Parameters about Hail Shooting and Heavy Convective Rainfall
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作者 陈金敏 刁秀广 《Agricultural Science & Technology》 CAS 2012年第11期2434-2437,2441,共5页
[Objective] The paper is to analyze physical quantities and radar parameter of hail shooting and heavy convective rainfall weather. [Method] Using radar data of Jinan station during 2002 and 2008, combined with soundi... [Objective] The paper is to analyze physical quantities and radar parameter of hail shooting and heavy convective rainfall weather. [Method] Using radar data of Jinan station during 2002 and 2008, combined with sounding data, the physical quantities and radar parameter of hail shooting and heavy convective rainfall weather are compared and analyzed. [Result] The smaller Sl is conducive to the generation of hail weather. When K〉 35 ~C, the probability for occurrence of heavy rainfall weather is significantly increased; when K〈20 ^(3, the probability for occurrence of heavy rainfall weather is significantly decreased. When CAPE value is greater than 1 500 J/KG, the probability for occurrence of hail weather is significantly decreased, while the probability for occurrence of heavy rainfall weather is significantly in- creased. The possibility for occurrence of hail monomer is small when the wind shear is less than 5 m/s; and it is large while wind shear is greater than 20 m/s. The radar forecasting indexes of hail monomer is as follows: VIL value reaches 35 kg/m2 (May), 43 kg/m2 (June and July), the monomer height is greater than 9 km, the maximum reflectivity factor is larger than 60 dBz, strong center height reaches 3.3 km (May), 4.3 km (June) and 5.5 km (July); VlL value of heavy rainfall monomer generally is below 25 kg/m2. [Conclusion] The paper provides basis form prediction of hail and heavy rainfall. 展开更多
关键词 HAIL Heavy convective rainfall VIL Weather radar parameter
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The effect of intra-trappean heterogeneities on seismic data: A case study from the Deccan Traps
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作者 Dhananjai Pandey Satish Singh +1 位作者 Martin Sinha Lucy MacGregor 《Applied Geophysics》 SCIE CSCD 2007年第3期183-193,共11页
Hydrocarbon exploration interests have renewed the need for developing new sub basalt imaging techniques. One of the most important problems encountered today is seismic imaging below basalt. In recent years, this pro... Hydrocarbon exploration interests have renewed the need for developing new sub basalt imaging techniques. One of the most important problems encountered today is seismic imaging below basalt. In recent years, this problem appears to have been overcome partly by using long offset seismic data. However near offset data are yet to be fully utilised due to the complex waveform caused by the surface as well as internal heterogeneity of the basalts. The near normal incidence data, which influence the sub-basalt imaging, are highly useful to understand the internal structure within a basalt layer. The use of converted waves for such targets has been proposed as an alternative in a rather homogeneous basalt layer. With a few synthetic modelling exercises here we highlight the practical difficulties in dealing with more realistic and heterogeneous basalt flow. Full waveform seismograms are computed to understand the effects of intra-trappean sediments on the seismic data. A case study from the Deccan Traps of India is presented in this paper. First, we discuss the effects of intercalated sediments on the overall seismic image. Later, the sonic log data from the field are used to compute the full wave-field response using the reflectivity method and compared with the field data. The feasibility of using mode converted waves (P to S and vice-versa at the top and bottom basalt interfaces) for sub-basalt imaging in Kutch region is discussed through a series of velocity-depth profiles. By comparing with the field data we demonstrate that the effects of multiple thin layering within the basalt can strongly deteriorate the image we seek to interpret and exploit. 展开更多
关键词 Sub-basalt imaging KUTCH Deccan Traps REFLECTIVITY Full-waveform modelling
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Estimation of As and Cu Contamination in Agricultural Soils Around a Mining Area by Reflectance Spectroscopy:A Case Study 被引量:32
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作者 REN Hong-Yan ZHUANG Da-Fang +3 位作者 A. N. SINGH PAN Jian-Jun QIU Dong-Sheng SHI Run-He 《Pedosphere》 SCIE CAS CSCD 2009年第6期719-726,共8页
Concentrations of Iron (Fe), As, and Cu in soil samples from the fields near the Baoshan Mine in Hunan Province, China, were analyzed and soil spectral reflectance was measured with an ASD FieldSpec FR spectroradiomet... Concentrations of Iron (Fe), As, and Cu in soil samples from the fields near the Baoshan Mine in Hunan Province, China, were analyzed and soil spectral reflectance was measured with an ASD FieldSpec FR spectroradiometer (Analytical Spectral Devices, Inc., USA) under laboratory condition. Partial least square regression (PLSR) models were constructed for predicting soil metal concentrations. The data pre-processing methods, first and second derivatives (FD and SD), baseline correction (BC), standard normal variate (SNV), multiplicative scatter correction (MSC), and continuum removal (CR), were used for the spectral reflectance data pretreatments. Then, the prediction results were evaluated by relative root mean square error (RRMSE) and coefficients of determination (R 2 ). According to the criteria of minimal RRMSE and maximal R 2 , the PLSR models with the FD pretreatment (RRMSE = 0.24, R 2 = 0.61), SNV pretreatment (RRMSE = 0.08, R 2 = 0.78), and BC-pretreatment (RRMSE = 0.20, R 2 = 0.41) were considered as the final models for predicting As, Fe, and Cu, respectively. Wavebands at around 460, 1 400, 1 900, and 2 200 nm were selected as important spectral variables to construct final models. In conclusion, concentrations of heavy metals in contaminated soils could be indirectly assessed by soil spectra according to the correlation between the spectrally featureless components and Fe; therefore, spectral reflectance would be an alternative tool for monitoring soil heavy metals contamination. 展开更多
关键词 data pre-processing heavy metal regression models soil iron spectral reflectance
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Intercomparison of Surface Radiative Fluxes in the Arctic Ocean
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作者 SHI Xiao-Xu LIU Ji-Ping 《Atmospheric and Oceanic Science Letters》 CSCD 2013年第6期434-439,共6页
Recent satellite data analysis has provided improved data sets relevant to the surface energy budget in the Arctic Ocean. In this paper, surface radiation properties in the Arctic Ocean obtained from the Surface Radia... Recent satellite data analysis has provided improved data sets relevant to the surface energy budget in the Arctic Ocean. In this paper, surface radiation properties in the Arctic Ocean obtained from the Surface Radiation Budget(SRB3.0) and the International Satellite Cloud Climatology Project(ISCCP-FD) during 1984– 2007 are analyzed and compared. Our analysis suggests that these datasets show encouraging agreement in basin-wide averaged seasonal cycle and spatial distribution of surface albedo; net surface shortwave and all-wave radiative fluxes; and shortwave, longwave, and all-wave cloud radiative forcings. However, a systematic large discrepancy is detected for the net surface longwave radiative flux between the two data sets at a magnitude of ~ 23 W m–2, which is primarily attributed to significant differences in surface temperature, particularly from April to June. Moreover, the largest difference in surface shortwave and all-wave cloud radiative forcings between the two data sets is apparent in early June at a magnitude of 30 W m–2. 展开更多
关键词 Arctic Ocean surface albedo surface radiative flux cloud forcing
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Optical closure of parameterized bio-optical relationships
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作者 贺双颜 FISCHER Jürgen +1 位作者 SCHAALE Michael 贺明霞 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2014年第2期480-489,共10页
An optical closure study on bio-optical relationships was carried out using radiative transfer model matrix operator method developed by Freie Universitat Berlin. As a case study, the optical closure of bio-optical re... An optical closure study on bio-optical relationships was carried out using radiative transfer model matrix operator method developed by Freie Universitat Berlin. As a case study, the optical closure of bio-optical relationships empirically parameterized with in situ data for the East China Sea was examined. Remote-sensing reflectance (Rrs) was computed from the inherent optical properties predicted by these biooptical relationships and compared with published in situ data. It was found that the simulated Rrs was overestimated for turbid water. To achieve optical closure, bio-optical relationships for absorption and scattering coefficients for suspended particulate matter were adjusted. Furthermore, the results show that the Fournier and Forand phase functions obtained from the adjusted relationships perform better than the Petzold phase function. Therefore, before bio-optical relationships are used for a local sea area, the optical closure should be examined. 展开更多
关键词 optical closure ocean color remote sensing bio-optical relationship
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利用GF-4 PMS数据反演城市地区气溶胶光学厚度 被引量:3
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作者 王艳莉 周斌 +3 位作者 应航 于之锋 张琳琳 宿鑫 《遥感技术与应用》 CSCD 北大核心 2019年第3期564-570,共7页
高分四号是我国发射的第一颗地球同步轨道卫星,具有较高的空间分辨率及快速重复成像能力,在城市大气环境的高动态监测方面拥有较大的应用潜力。针对城市地区地表反射率高、地表类型复杂,传统的单一算法较难实现大气气溶胶光学厚度有效... 高分四号是我国发射的第一颗地球同步轨道卫星,具有较高的空间分辨率及快速重复成像能力,在城市大气环境的高动态监测方面拥有较大的应用潜力。针对城市地区地表反射率高、地表类型复杂,传统的单一算法较难实现大气气溶胶光学厚度有效反演等问题,以北京市为研究区,使用了一种暗目标法和地表反射率数据库相结合的方法,分别对2017年5月25日和10月5日两个时相的气溶胶光学厚度进行了估算。结果表明,该方法能够有效实现城市暗目标区和亮目标区的气溶胶反演,且与MODIS标准陆地气溶胶产品及AERONET站点地面观测数值较为一致,相关系数超过了 0.9。 展开更多
关键词 GF-4PMS 暗目标算法 地表反射率数据 气溶胶光学厚度
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一种拓展的半物理时空融合算法及其初步应用 被引量:7
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作者 李大成 唐娉 +1 位作者 胡昌苗 郑柯 《遥感学报》 EI CSCD 北大核心 2014年第2期307-319,共13页
Landsat 5卫星较低的时间分辨率(16天)使得其很难获得大区域的、时相一致的清晰影像数据集。本文发展了一种基于半物理模型的时空融合算法-即乘性调制融合算法,并借助多时序的MODIS反射率数据来生成多时相的Landsat TM/ETM+反射率合成影... Landsat 5卫星较低的时间分辨率(16天)使得其很难获得大区域的、时相一致的清晰影像数据集。本文发展了一种基于半物理模型的时空融合算法-即乘性调制融合算法,并借助多时序的MODIS反射率数据来生成多时相的Landsat TM/ETM+反射率合成影像,经镶嵌后得到区域尺度的高时空分辨率地表反射率数据集(Landsat TM/ETM+)。本文利用吉林省2006年—2011年的Landsat 5 TM地表反射率数据以及500 m的MOD09A1反射率产品来生成3个时相的Landsat 5 TM反射率合成数据,从而获得研究区在上述时相下地表反射率数据的镶嵌图。初步分析表明,所生成的Landsat 5 TM反射率数据的光谱分布特征与MOD09A1反射率数据较为一致,且图像在整体上光谱特征的连续性较好。 展开更多
关键词 时空融合 半物理模型 乘性调制 LANDSAT TM ETM+ MODIS 地表反射率数据
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北京地区Landsat 8 OLI高空间分辨率气溶胶光学厚度反演 被引量:23
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作者 田信鹏 孙林 +1 位作者 刘强 李秀红 《遥感学报》 EI CSCD 北大核心 2018年第1期51-63,共13页
卫星气溶胶光学厚度(AOD)反演中,传统暗目标方法在反射率较低的水体、浓密植被覆盖区域取得了较好效果,在反射率较高且结构复杂的高反射地表上空目前多采用深蓝算法,但存在空间分辨率较低,对细节分布描述性较差等问题。为解决这一问题,... 卫星气溶胶光学厚度(AOD)反演中,传统暗目标方法在反射率较低的水体、浓密植被覆盖区域取得了较好效果,在反射率较高且结构复杂的高反射地表上空目前多采用深蓝算法,但存在空间分辨率较低,对细节分布描述性较差等问题。为解决这一问题,本文首先以5年(2008年—2012年)长时间序列MODIS地表反射率产品为基础,采用最小值合成法建立500 m分辨率逐月地表反射率产品数据集,然后利用地物波谱库中典型地物波谱数据,分析建立MODIS与Landsat 8 OLI传感器蓝光波段反射率转换模型,最后北京地区AERONET地基观测数据确定了气溶胶光学物理参数,并反演获取了北京地区上空500 m分辨率的AOD分布。为验证反演算法的精度,分别将反演结果同AERONET及MODIS/Terra气溶胶产品(MOD04)进行交叉对比,同时利用相关系数R,均方根误差RMSE,平均绝对误差MAE以及MODIS AOD产品预期误差EE共4个指标进行衡量。结果表明:算法反演获取的AOD与AERONET观测值具有较高的一致性,各指标分别为R=0.963,RMSE=0.156,MAE=0.097,EE=85.3%,稍优于MOD04产品(R=0.962,RMSE=0.158,MAE=0.101,EE=75.8%),并且有效的对比点数也高于MOD04。通过与地基观测相比,卫星遥感获取的高分辨率城市地区AOD精度可作为定量评估城市空气质量的有效依据。 展开更多
关键词 气溶胶光学厚度 光谱转化 地表反射率数据 LANDSAT 8 OLI AERONET
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Retrieval of aerosol optical depth over bright targets in the urban areas of North China during winter 被引量:11
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作者 LI ShenShen CHEN LiangFu +5 位作者 TAO JinHua HAN Dong WANG ZhongTing SU Lin FAN Meng YU Chao 《Science China Earth Sciences》 SCIE EI CAS 2012年第9期1545-1553,共9页
Two factors that affect satellite retrieval of Aerosol Optical Depth(AOD) are aerosol model assumptions and the separation of surface reflectance.NASA/MODIS Dense Dark Vegetation(DDV) algorithm has been proven valuabl... Two factors that affect satellite retrieval of Aerosol Optical Depth(AOD) are aerosol model assumptions and the separation of surface reflectance.NASA/MODIS Dense Dark Vegetation(DDV) algorithm has been proven valuable in deriving aerosol distribution and properties over land;however,it cannot be applied to bright targets.As a supplement to the DDV algorithm,an algorithm to retrieve AOD over urban areas in North China in winter is developed using MODIS data,including(1) the generation and analysis of adjacent clear-days surface reflectance using MOD09 product from 2007 to 2008,and(2) seasonal aerosol models derived from AERONET data in Beijing and Xianghe sites.Ground-based measurements using sun photometers were used to validate the retrieved AOD,and the correlation coefficient(r) is up to 0.931.Especially for high AOD values(AOD>0.4),more retrievals meet the inversion accuracy.The temporal variations of retrieval errors over urban,rural and mountain regions were examined,and the results indicated that the variation of blue-band surface reflectance is less than 0.02 in a short period except for unusual weather conditions,the retrieval bias is under 0.08,and the relative error decreases as the AOD increases. 展开更多
关键词 aerosol optical depth MODIS surface reflectance bright targets
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Method study and uncertainty analysis of calibration coefficients validation based on the Inner Mongolia test site 被引量:1
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作者 GAO HaiLiang GU XingFa +3 位作者 YU Tao GONG Hui LI JiaGuo LI XiaoYing 《Science China Earth Sciences》 SCIE EI CAS 2013年第9期1540-1547,共8页
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 validati... 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. 展开更多
关键词 Method study and uncertainty analysis of calibration coefficients validation based on the Inner Mongolia test site
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Estimating biophysical parameters of rice with remote sensing data using support vector machines 被引量:13
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作者 YANG XiaoHua HUANG JingFeng +4 位作者 WU YaoPing WANG JianWen WANG Pei WANG XiaoMing Alfredo R. HUETE 《Science China(Life Sciences)》 SCIE CAS 2011年第3期272-281,共10页
Hyperspectral reflectance (350-2500 nm) measurements were made over two experimental rice fields containing two cultivars treated with three levels of nitrogen application.Four different transformations of the reflect... Hyperspectral reflectance (350-2500 nm) measurements were made over two experimental rice fields containing two cultivars treated with three levels of nitrogen application.Four different transformations of the reflectance data were analyzed for their capability to predict rice biophysical parameters,comprising leaf area index (LAI;m-2 green leaf area m-2 soil) and green leaf chlorophyll density (GLCD;mg chlorophyll m 2 soil),using stepwise multiple regression (SMR) models and support vector machines (SVMs).Four transformations of the rice canopy data were made,comprising reflectances (R),first-order derivative reflectances (D1),second-order derivative reflectances (D2),and logarithm transformation of reflectances (LOG).The polynomial kernel (POLY) of the SVM using R was the best model to predict rice LAI,with a root mean square error (RMSE) of 1.0496 LAI units.The analysis of variance kernel of SVM using LOG was the best model to predict rice GLCD,with an RMSE of 523.0741 mg m-2.The SVM approach was not only superior to SMR models for predicting the rice biophysical parameters,but also provided a useful exploratory and predictive tool for analyzing different transformations of reflectance data. 展开更多
关键词 biophysical parameters support vector machines remote sensing
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Calibration of ASTER and ETM + Imagery Using Empirical Line Method——A Case Study of North-East of Hajjah, Yemen
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作者 ALI M. Qaid BASAVARAJAPPA H T +1 位作者 RAJENDRAN S ASHFAQ S A 《Geo-Spatial Information Science》 2009年第3期197-201,共5页
This study is aimed at using the Empirical Line Method (ELM) to eliminate atmospheric effects with respect to visible and near infrared bands of advanced spaceborne thermal emission and reflection radiometer (ASTER... This study is aimed at using the Empirical Line Method (ELM) to eliminate atmospheric effects with respect to visible and near infrared bands of advanced spaceborne thermal emission and reflection radiometer (ASTER) and enhanced thematic mapper plus (ETM+) data. Two targets (Amran limestone as light target and quartz-biotite-sericite-graphite schists as dark target), which were widely exposed and easy to identify in the imagery were selected. The accuracy of the atmospheric correction method was evaluated from three targets (vegetation cover, Amran limestone and Akbra shale) of the surface reflectance. Analytical spectral devices (ASD) FieldSpec3 was used to measure the spectra of target samples. ETM+ data were less influenced by the atmospheric effect when compared to ASTER data. Normalized differences vegetation indices (NDVI) displayed good results with reflectance data when compared with digital number (DN) data because it is highly sensitive to ground truth reflectance (GTR). Most of the differences observed before and after calibration of satellite images (ASTER and ETM+) were absorbed in the SWlR region. 展开更多
关键词 ELM ASTER ETM+ GTR FieldSpec3
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