彩红外航空像片应用于森林灾害调查的方法与结果分析     

唐小平 《遥感学报》1991,(1)

本文应用联邦德国的一个实例,介绍了大比例尺(1:5000)彩红外航空像片应用于森林灾害调查的程序和方法。总结了彩红外航空像片判读树种和林木受损害等级的标志;并分析了不同树种、年龄和海拔高度等因素对林木受损害程度的影响;最后提出了调查精度。结果表明:利用彩红外航空像片调查林木因大气污染、病虫害、自然灾害等因子影响而受损的程度的方法,可以为合理经营规划森林资源快速提供较精确的信息。  相似文献   

Analysis of magnetic data over part of the Younger Granite Province of Nigeria     

Charles O. Ofoegbu  Karin Hein 《Pure and Applied Geophysics》1991,136(2-3):173-189

The results of a magnetic study of part of the Younger Granite Province of Nigeria are presented here. Spectral analysis of the magnetic anomalies over the area has been carried out in an effort to estimate the depth to magnetic sources. Average magnetic source depth of 286 m has been obtained for the area and this is thought to be related to the depth to the top of the main anomalous structures in the area. Observed magnetic anomaly profiels taken across the area have been interpreted in terms of arbitrarily shaped bodies—whose existence was confirmed by 3-D Hilbert transformation-using nonlinear optimization techniques. The modelled bodies occur at depths of 200–760 m and have magnetizations of 0.29–0.47 A/m. The results from the analysis of the magnetic field are discussed in relation to the results from previous gravity studies over the area and the mode of emplacement of the Younger Granites.  相似文献   

Spanish national strong motion network. Recording of the Huelva earthquake of 20 December, 1989     

E. Carreño  J. Rueda  C. López Casado  J. Galán  J. A. Peláez 《Pure and Applied Geophysics》1991,136(4):395-404

In recent years a network of 30 accelerographs has been installed through the zones of highest seismic activity of Spain. For the first time, digital strong motion records have been obtained in Spain, with a maximum horizontal acceleration value of 0.06 g. A comprehensive study is made of the strong motion recordings of an earthquake which occurred in southwest Spain, on December 20, 1989. The isoseismal map is drawn and the data confirm the main attenuation directions in the area observed in other shocks.  相似文献   

Least-squares collocation, geophysical inverse theory and geostatistics: a bird's eye view   总被引：1，自引：0，他引：1  

Ute Christina Herzfeld 《Geophysical Journal International》1992,111(2):237-249

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WIND WAVES SIMULATION IN THE NORTH AREA OF THE SOUTH CHINA SEA   总被引：1，自引：1，他引：1  

王文质  陈俊昌  黎满球  李毓湘  李志伟 《中国海洋湖沼学报》1992,10(2):107-118

A third generation wave model was developed to simulate wind waves in the South China Sea near Hong Kong. The model solves the energy conservation equation of the two dimensional wave spectrum by directly computing the nonlinear energy interaction among waves of different frequencies, thus avoiding the imposition of restrictions on the shape of the predicted spectra. The use of an upwind difference scheme in the advective terms produces an artificial diffusion which partly compensates the dispersive effect due to the phase velocity differences among various wave components. The use of a semi-implicit scheme for the source terms together with a special treatment of the high frequency tail of the spectrum allows a large time integration step. Verification of the model was done for wave hindcasting studies under conditions of two typhoons and two cold fronts in the north part of the South China Sea near Hong Kong . The model results agree well with the field measurements except that the presence of a dista  相似文献   

三河—平谷地区地脉动H/V谱比法探测:场地响应、浅层沉积结构及其反映的断层活动          下载免费PDF全文

彭菲  王伟君  寇华东 《地球物理学报》1954,63(10):3775-3790

1679年三河—平谷8级地震,造成了包括北京在内的华北广大地区严重的人员和经济损失,但是该地区和地震灾害密切相关的沉积结构和地震场地响应特征研究,相对比较缺乏.本文利用1~4 km台间距的高密度单台地脉动观测、几个小孔径台阵观测和钻孔测井数据,研究了三河—平谷地区的浅层沉积的场地响应和沉积层三维起伏特征,以及构造运动对沉积厚度的影响.结果表明,研究区沉积层的场地共振频率和沉积厚度有明显的分区特征：东北部场地共振频率主要在1.0~7.0 Hz之间,具有相对较薄的沉积厚度,沉积界面起伏也相对平稳;西南部场地共振频率大部分区域小于1.0 Hz,可低至0.3 Hz,相应的沉积厚度起伏显著,其中在大厂凹陷厚度可达300~600 m.沉积起伏和隐伏断裂带的分布有较好的对应关系,反映了夏垫断裂、南苑—通县断裂第四纪以来较为活跃的正断活动.北东走向的夏垫等隐伏断裂在东北部山前的正断活动相对不发育,以及东北部和西南部沉积厚度的显著差异,都可能受到北西走向的二十里长山断裂带活动的影响.按照Vs30场地分类,研究区内沉积较厚的凹陷地区主要为E类软土,其他区域为D类中硬土.研究结果与区域地质调查、钻孔数据和浅层地震勘探剖面结果基本相符,说明地脉动探测方法能够高效、低成本的获取区域沉积厚度和场地作用,为地震小区划和抗震设防提供有意义的参考.  相似文献   

基于波段组合的高光谱数据湿地分类研究     

乔雯钰  龙亦凡  付杰 《北京测绘》2020,(5):651-656

对高光谱数据进行波段组合,可以减少信息量的冗余,提高数据的处理速度。对黄河口入海口湿地进行分类,对合理利用、开发保护该地区湿地资源具有重要意义。本文首先分析了“珠海一号”高光谱数据各个波段的信息量及波段之间的相关系数,然后利用最佳波段指数(OIF)方法选出波段组合B7-B8-B32,进一步在OIF基础上设置信息量与相关系数阈值,选出波段组合B7-B18-B32,实验结果证明分类精度提高了5.4%。最后,根据地物的光谱特征分析,选择光谱差异较大的波段进行组合B6-B13-B18,分类后精度比OIF筛选出的波段组合精度高12.6694%。经实验验证,结合地物光谱特征的波段组合可以大大提高分类精度。  相似文献   

考虑目标光谱差异的机载离散激光雷达叶面积指数反演   总被引：1，自引：0，他引：1  

田罗  屈永华  Korhonen Lauri  Korpela Ilkk  Heiskanen Janne 《遥感学报》2020,24(12):1450-1463

利用间隙率模型反演LAI（Leaf Area Index），需要同时获取冠层间隙率和消光系数，后者与冠层叶倾角分布有关。基于点云数量构建激光雷达穿透指数LPI （LiDAR Penetration Index），用以代替冠层间隙率GF （Gap Fraction），并利用间隙率模型反演冠层LAI是利用LiDAR PCD（LiDAR Point Cloud Data）数据反演冠层LAI主要思路。冠层和背景的光谱差异是影响PCD数据中冠层和背景点云数量的重要因素，因此从LPI到GF的校正需要获取背景和冠层的后向散射系数比（μ=ρg/ρv）。本文基于PCD数据中点云强度进行μ值获取，用以实现LPI到GF的校正；在假设区域内叶倾角满足椭球形叶倾角分布的基础上，利用样地尺度下的多角度GF，采用有约束的非线性最优化方法获取椭球形叶倾角分布参数χ，实现冠层消光系数的获取；最后利用间隙率模型实现基于PCD数据的LAI反演。本文探讨了基于PCD数据进行冠层LAI反演时，样地尺度Rxy_Tile、样方尺度Rxy_Plot以及进行背景和冠层分割的高度阈值Ht对模型的影响。结果显示，由于区域内地衣植被广泛覆盖，基于点云强度的μ 值接近1，符合区域特点；经过μ值校正后的GF对冠层间隙率具有较好的反映能力（R2=0.78,RMSE=0.09）；对于优势种明显的区域，基于样地尺度内多角度GF的χ值反演受样地内冠间大间隙的影响，选择合适的样地尺度能够减小LAI反演过程中的系统性误差；结合地面参考数据，确定的最优Rxy_Tile、Rxy_Plot和Ht分别为950 m、10 m和2.6 m，在此基础上反演的LAI与地面测量数据具有高度的一致性（R2=0.84,RMSE=0.51）；与Rxy_Plot相比，基于间隙率模型的LAI反演对Ht的选择更为敏感。  相似文献   

Turbulent Dissipation Rate In The Boundary Layer Via Uhf Wind Profiler Doppler Spectral Width Measurements   总被引：2，自引：0，他引：2  

B. Campistron  S. Bernard  B. Bénech  F. Ardhuin-Girard  J. Dessens  E. Dupont  B. Carissimo 《Boundary-Layer Meteorology》2002,103(3):361-389

The study is focused on the retrieval and validation of the turbulent kinetic energy dissipation rate from spectral width measurements made by a UHF wind profiler in the convective atmospheric boundary layer. The possibility to deduce , which is one of the most important parameters for boundary-layer study and monitoring, from Doppler radar spectral width measurements has a firm theoretical basis established by numerous earlier works. However, the major drawback of this approach lies in various meteorological and instrumental sources of non-turbulent spectral width broadening which have to be recognised and accounted for. In the first part of the study, the theoretical background of the retrieval is detailed and all possible causes of spectral broadening are listed and evaluated. In the second part, the method is applied to four days of UHF diurnal boundary-layer observations, collected during the TRAC-98 experiment, for which in situ aircraft measurements were available. Comparison between radar-retrieved and in situ aircraft measurements yields a fairly good agreement with a linear correlation coefficient of about 0.9 and a residual bias less than 2 × 10^-4 m² s^-3. The analysis of derived from vertical and off-zenith observation leads to the recommendation, that in the boundary layer, where the wind is usually moderate, data collected by off-zenith beams should be used. Indeed, the measurement of the vertical spectral width, less affected by the large-scale broadening factor, can still be altered by the ground clutter removal.  相似文献   

基于地物光谱特征的成像光谱遥感矿物识别方法   总被引：16，自引：0，他引：16  

张宗贵  王润生  郭小方  甘甫平  杨苏明 《地学前缘》2003,10(2):437-443

成像光谱技术是遥感技术发展的前沿技术之一 ,它是在可见光、近红外及短波红外上 ,集图像、光谱于一体的具有高光谱分辨率的纳米遥感技术。文中从岩矿光谱特性的研究入手 ,通过光谱特征识别准则 ,利用机载的可见光、近红外及短波红外成像光谱 (HyMap)数据 ,开展成像光谱遥感矿物识别的试验研究。试验识别的矿物有绿泥石、绿帘石、橄榄石、绢云母、滑石、石膏及黑云母等。试验结果表明 ,通过矿物光谱特征分析与其识别原则进行成像光谱遥感矿物识别获得了很好的效果。因此 ,基于地物光谱特征进行成像光谱矿物直接识别确实可行 ,有利于矿产资源评价中成矿物源和矿化蚀变信息分析。  相似文献