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基于时间序列统计特性的森林变化监测 总被引：1，自引：0，他引：1
森林动态变化分析对揭示生态系统环境变化及植被恢复和布局重建等具有重要意义,时间序列的遥感数据为森林监测提供了基础数据。本文根据森林植被的统计学特性,在暗目标法的基础上,利用归一化植被指数NDVI实现森林样本自动选择;并融合NDVI构建了新的综合森林特征指数(Integrated Forest Z-Score,IFZ);以时间序列的IFZ分析森林动态信息,实现森林变化动态监测。以三峡大坝及周边区域森林为研究区,利用2001年至2012年每年生长季节(5月—10月)的Landsat TM影像检验本文算法。基于2002年、2006年和2010年三期7月—9月的Quick Bird影像的精度分析结果发现:研究区森林变化检测的总体精度可达96.53%,Kappa系数为0.9512。在添加NDVI指数后构建的IFZ提高了总体监测精度。其中,毁林类别的检测精度提高显著,漏检率和误检率分别为2.74%和3.64%;干扰后重建的森林类别的检测精度有一定提高,其漏检率和误检率分别为10.79%和10.51%。研究结果表明,改进暗目标法能提高森林样本的选样效率,添加NDVI的IFZ能提高森林动态变化的识别度。此外,本算法不仅能定性识别森林变化,而且能定量提供森林干扰发生时间和干扰强度。 相似文献
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Solar Physics - A curved filament in a decaying active region (AR&;nbsp;8329) was observed on 9 September 1998 with a combination of several instruments. The main data base is a 4-hour long time... 相似文献
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随着传感器技术的发展,高光谱数据光谱的波段宽度逐渐变窄,如何从海量的光谱数据中找到最优的光谱波段反演叶绿素含量,成为研究的难点问题。本文在测量华中农业大学狮子山6种主要树种的光谱数据和叶绿素含量的基础上,利用叶绿素指数(CI)和回归方法反演叶绿素含量,并分析了波段宽度对反演叶绿素含量结果的影响,结果发现波段宽度会影响到叶绿素反演的精度,当波段宽度为30nm时,叶绿素含量与"红边"区域(700nm-730nm)和近红外区域(770nm-800nm)叶绿素指标(CI)间的线性关系较好,决定系数可达到77.62%,均方根误差为10.6ug/cm2。 相似文献
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Sequential observations at Huairou Solar Observation Station, China, and Kitt Peak, U.S.A., show that polar magnetic elements can live from several to more than 58 hours. This enables measurement of the solar rotation rate near the polar region by tracing magnetic element motions. With observations carried out on 8–15 July 1997, we identify and trace more than 1300 elements at north heliographic latitudes between 55°–85° using two methods, and fit the mean sidereal rotation rate as =14.0±0.54–(2.24±1.22)sin2–(1.78±0.79)sin4 deg per day. 相似文献
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Comparison of the Different Classifiers in Vegetation Species Discrimination Using Hyperspectral Reflectance Data 总被引：1，自引：0，他引：1
Yuanyong Dian Shenghui Fang Yuan Le Yongrong Xu Chonghuai Yao 《Journal of the Indian Society of Remote Sensing》2014,42(1):61-72
Feature selection methods play an important role in Hyperspectral Remote Sensing applications, especially in classification. This paper proposed a new Feature selection strategy for Hyperspectral dataset. This strategy was designed to help refine vegetation classification of 4 categories with 13 species vegetation which are the most common species in central China. An ASD field spectrometer (Analytical Spectral Device) was used to collect spectrum information of plant leaves from each species through 400 nm to 900 nm with 1 nm spectral resolution. Firstly, correlation between the physical/chemical characteristics of the leaves and the separability of each vegetation species was tested. Then, two feature selection methods, spectral angle and spectral distance, and the feature parameters extracted from spectral curves (FPESC) were used to build the feature space which would be the input space for the classifiers. At last, two linear classifiers, mahalanobis distance (MDC), and fisher linear discriminate analysis (FLDA), and a quadratic classifier, maximum likelihood (MLC), were used for vegetation species refine classification. The results showed that (1) there were no significant differences among 13 species on the leaf dry weight (physical parameter) and leaf chlorophyll content (chemical parameter); (2) FPESC of 13 species have distinctive differences and could be ideal features to discriminate these species; (3) The linear classifiers, MDC and FLDA, have better classification results in the experiments compared to the quadratic classifier MLC, where MDC has the highest classification accuracy which is above 96.2 %. 相似文献
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基于Python的ArcGIS地理数据批处理 总被引：1，自引：0，他引：1
ArcGIS地理处理工具一般只针对单个数据集执行,而运用Python脚本语言可以实现地理数据的批处理。本文以原始DEM影像插值生成特定空间分辨率的DEM影像为例,给出数据批处理的具体实现过程。 相似文献
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Shuo Wang Yuanyong Deng Rajmal Jain Vasyl Yurchyshyn Haimin Wang Yuanyuan Liu Zhiliang Yang 《Journal of Astrophysics and Astronomy》2008,29(1-2):57-61
In this paper, we study the evolution of vector magnetic field of AR 10656 by using the observations of Huairou Solar Observing Station (HSOS, China) and Big Bear Solar Observatory (BBSO, USA). The magnetic flux emergence and cancellation, and thus, magnetic nonpotential changes, are associated with the major flares in this active region. Compared with some other super-active regions, the evolution of magnetic morphologies and non-potentialities are relatively gradual, and thus the energy transportation and release are relatively slow. This gradual process may result in the recurrent flares of AR 10656. 相似文献
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Based on photospheric vector magnetograms obtained at Huairou Solar Observing Station, we have studied the evolution of magnetic
nonpotentiality in NOAA AR 9077 from 11 to 15 July 2000. We focus our analysis on the daily change of nonpotential characteristics
in the photospheric magnetic field preceding the `Bastille Day' flare. We have identified the following evolving patterns:
(1) The shear-angle distribution underwent dramatic change in the filament channel. At a key site of the filament environment,
the magnetic shear changed sign from positive to negative. (2) The old current systems disrupted, and new but weaker systems
formed before this major event. Similar changes are identified for the longitudinal current helicity. (3) The source field
weakened before the flare, and the density of free magnetic energy decreased at the photospheric level. These obvious changes
lasted at least nine hours before the `Bastille Day' flare, and they took place where a large amount of magnetic flux disappeared
in magnetic flux cancellation. The site of dramatic changes is also found to coincide with the base of helical magnetic ropes
which were seen in a 3-D force-free reconstruction. We suggest that the observed evolution of the magnetic nonpotentiality
represents a continuous transportation of magnetic energy and complexity from the lower atmosphere to the corona. This transportation
seems to be responsible for the energy build-up for the major flare. Moreover, the slow magnetic reconnection in the lower
atmosphere, observed as magnetic flux cancellation, appears to play a key role in this energy build-up process.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1014258426134 相似文献