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针对光学相机通信中存在的图像传感器有效像素受限以及多帧通信之间存在的通信不连续问题,提出利用高分辨率图像传感器在单帧图像中完整接收数据包的非视线信道通信方案.非视线信道的方案解决光源造成的blooming效应问题,并增加了图像传感器上的通信有效像素.同时,通过高精度的同步算法和多列信号累积,克服非视线信道带来的大衰减问题.高分辨率图像传感器可感知更高速的信号变化,从而有助于同步精度和通信速率的提高.实验结果表明:该方案可实现1.5 m距离上的2.15 kpbs通信速率,单帧内数据包长度为16 bit,满足室内定位导航、光子标记等应用需求. 相似文献
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该文首先介绍了大面积降水的多普勒天气雷达径向速度PPI图像识别技术, 包括:①冷暖平流与大尺度辐合辐散运动叠加的图像特征; ②由零线的朝向和正负速度面积、径向速度值的大小判断风向风速辐合辐散的图像特征, 然后介绍了利用EVAD技术由雷达基数据定量计算大气平均散度和平均垂直速度的方法, 最后应用图像识别技术和EVAD方法对石家庄2004年冬季的一次大面积降雪过程进行了详细分析, 发现:此次大面积降雪过程有明显的辐合辐散图像特征, 径向速度值小, 辐合辐散弱, 始终存在暖平流。另外, 降雪强度和散度、垂直速度关系密切:辐合层厚度加大, 辐散抬高, 则降雪加强; 辐合、辐散层高度降低, 则降雪减弱。同时, 由EVAD技术定量计算的散度和相同时刻由径向速度图像产品定性分析的辐合、辐散基本一致。 相似文献
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当前基于卷积神经网络(CNN)的超分辨率(SR)重建算法,虽然取得了很大的成功,但是重建图像高频纹理的效果仍然不能令人满意,其高分辨率(HR)图像局部边缘存在明显的震荡.本文提出一种结合形态学成分分析(MCA)分解的边缘指导双通道CNNSR算法:待处理的低分辨率(LR)图像通过MCA分解为纹理部分和平滑结构部分;纹理部分和原LR图像共同组成双通道,输入到改进的网络结构中重建HR纹理部分;结合HR纹理输出与LR平滑结构部分重建HR图像.训练过程采用最小化纹理损失与原图像损失之和最优化网络模型参数.后处理包括:执行网络输出与LR输入图像的直方图匹配使色调保持一致,提升感官效果;应用迭代的反向映射使HR重建与LR输入保持退化算子一致性提高PSNR值.实验结果显示:该方法能够很好地恢复HR图像的纹理细节,对纹理细节丰富的图像恢复效果更好. 相似文献
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Shengli Huang Devendra Dahal Ramesh Singh Heping Liu Claudia Young Shuguang Liu 《Theoretical and Applied Climatology》2013,113(3-4):549-560
Extrapolating energy fluxes between the ground surface and the atmospheric boundary layer from point-based measurements to spatially explicit landscape estimation is critical to understand and quantify the energy balance components and exchanges in the hydrosphere, atmosphere, and biosphere. This information is difficult to quantify and are often lacking. Using a Landsat image (acquired on 5 August 2004), the flux measurements from three eddy covariance flux towers (a 1987 burn, a 1999 burn, and an unburned control site) and a customized satellite-based surface energy balance model of Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC), we estimated net radiation, sensible heat flux (H), latent heat flux (LE), and soil heat flux (G) for the boreal Yukon River Basin of Interior Alaska. The model requires user selection of two extreme conditions present within the image area to calibrate and anchor the sensible flux output. One is the “hot” condition which refers to a bare soil condition with specified residual evaporation rates. Another one is the “cold” condition which refers to a fully transpiring vegetation such as full-cover agricultural crops. We selected one bare field as the “hot” condition while we explored three different scenarios for the “cold” pixel because of the absence of larger expanses of agricultural fields within the image area. For this application over boreal forest, selecting agricultural fields whose evapotranspiration was assumed to be 1.05 times the alfalfa-based reference evapotranspiration as the “cold” pixel could result in large errors. Selecting an unburned flux tower site as the “cold” pixel could achieve acceptable results, but uncertainties remain about the energy balance closure of the flux towers. We found that METRIC performs reasonably well in partitioning energy fluxes in a boreal landscape. 相似文献
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为了提升机器人工程专业学生综合实践能力,本文设计了一款集机、电、控、图像处理于一体的教学机器人实验平台,将机器人机械结构设计、运动学分析、运动控制、图像处理等技术有机融合,不仅提供了机器人关节装配及实物图演示实验,易于学生理论联系实际深入掌握机器人机械结构及工作原理,而且基于开放的控制实验平台,能够完成机器人的运动学分析、驱动控制、轨迹规划、图像处理及基于视觉引导的物体识别与抓取等实验.该实验平台具有很强的综合性和可操作性,激发了学生的学习兴趣,使学生工程实践与创新能力得到有效提升. 相似文献
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该文分析了卫星云图和自然图像在小波系数分布上的特征差异,提出了基于小波变换的气象卫星云图压缩方案。方案选择对卫星云图压缩效果较好的、具有双正交性的Odegard 9/7滤波器组对卫星云图进行五级小波分解和重构;根据卫星云图小波分解系数相似性强、低频分量能量更为集中、分量系数层次衰减性明显的特点,使用改进后的零树编码算法对小波系数进行编码运算;最后,采用高效的自适应算术编码对输出数据流进行了进一步的压缩。该方法对卫星云图的压缩效果要优于经典的嵌入式零树小波编码,在失真允许情况下,对红外云图的最大压缩比可达40:1,水汽云图达60:1,可见光云图达35:1。 相似文献
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A modified Becker’s split-window approach for retrieving land surface temperature from AVHRR and VIRR
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In order to provide a long time-series,high spatial resolution,and high accuracy dataset of land surface temperature(LST) for climatic change research,a modified Becker and Li’s split-window approach is proposed in this paper to retrieve LST from the measurements of Advanced Very High Resolution Radiometer(AVHRR) onboard National Oceanic and Atmospheric Administration(NOAA)-7 to-18 and the Visible and InfraRed Radiometer(VIRR) onboard FY-3A.For this purpose,the Moderate Resolution Transmittance Model(MODTRAN) 4.1 was first employed to compute the spectral radiance at the top of atmosphere(TOA) under a variety of surface and atmosphere conditions.Then,a temperature dataset consists of boundary temperature T s(which is one of the input parameters to MODTRAN),and channels 4 and 5 brightness temperatures(T 4 and T 5) were constructed.Note that channels 4 and 5 brightness temperatures were simulated from the MODTRAN output spectral radiance by convolving them with the spectral response functions(SRFs) of channels 4 and 5 of AVHRRs and VIRR.The coefficients of modified Becker and Li’s split-window approach for various AVHRRs and VIRR were subsequently regressed based on this temperature dataset using the least square method.As an example of validation,one AVHRR satellite image over Beijing acquired at 0312 UTC 27 April 2008 by AVHRR onboard NOAA-17 was selected to retrieve the LST image using the modified Becker and Li’s approach.The comparison between this LST image and that from the MODIS level-2 LST product provided by the University of Tokyo in Japan indicates that the correlation coefficient is 0.88,the bias is 0.6 K,and the root mean square deviation(RMSD) is 2.1 K.Furthermore,about 70% and 37% pixels in the LST difference image,which is the result of retrieved LST image from AVHRR minus the corresponding MODIS LST image,have the values within ± 2 and ± 1 K,respectively. 相似文献
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A Modified Becker''s Split-Window Approach for Retrieving Land Surface Temperature from AVHRR and VIRR 总被引:1,自引:0,他引:1
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QUAN Weijun CHEN Hongbin HAN Xiuzhen LIU Yonghong YE Caihua 《Acta Meteorologica Sinica》2012,26(2):229-240
In order to provide a long time-series, high spatial resolution, and high accuracy dataset of land surface
temperature (LST) for climatic change research, a modified Becker and Li's split-window approach is pro-
posed in this paper to retrieve LST from the measurements of Advanced Very High Resolution Radiometer
(AVHRR) onboard National Oceanic and Atmospheric Administration (NOAA)-7 to -18 and the Visible and
InfraRed Radiometer (VIRR) onboard FY-3A. For this purpose, the Moderate Resolution Transmittance
Model (MODTRAN) 4.1 was first employed to compute the spectral radiance at the top of atmosphere
(TOA) under a variety of surface and atmosphere conditions. Then, a temperature dataset consists of
boundary temperature Ts (which is one of the input parameters to MODTRAN), and channels 4 and 5
brightness temperatures (T4 and T5) were constructed. Note that channels 4 and 5 brightness tempera-
tures were simulated from the MODTRAN output spectral radiance by convolving them with the spectral
response functions (SRFs) of channels 4 and 5 of AVHRRs and VIRR. The coefficients of modified Becker
and Li's split-window approach for various AVHRRs and VIRR were subsequently regressed based on this
temperature dataset using the least square method. As an example of validation, one AVHRR satellite image
over Beijing acquired at 0312 UTC 27 April 2008 by AVHRR onboard NOAA-17 was selected to retrieve
the LST image using the modified Becker and Li's approach. The comparison between this LST image and
that from the MODIS level-2 LST product provided by the University of Tokyo in Japan indicates that
the correlation coefficient is 0.88, the bias is 0.6 K, and the root mean square deviation (RMSD) is 2.1 K.
Furthermore, about 70% and 37% pixels in the LST difference image, which is the result of retrieved LST
image from AVHRR minus the corresponding MODIS LST image, have the values within ±2 and ±1 K,
respectively. 相似文献
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Summary The sky view factor (SVF) is used in forest, road and urban climatology to characterise radiative properties. We now propose
a method suitable for forest canopies using the raster based and commercially available software IDRISI. It uses quadratic
pixels in rows and columns in a scanned equiangular fish-eye image. A threshold value is chosen to divide the image into sky
and non-sky areas. The resulting image is then multiplied with a sky view weight image, where the weights of the pixels depend
on the angular distance from zenith. The sum of pixel products gives the SVF. Quality analysis of the method is also performed.
The choice of threshold value gives some uncertainties due to leaves reflecting sunlight. This error will be reduced by observing
details (branches etc.) in the image and by choosing an overcast day for capturing the image. The precision range for SVF
calculations will be better than 0.1.
Received November 22, 1999 Revised July 17, 2000 相似文献
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图像分割是计算机视觉中基础且重要的一个问题.熵阈值图像分割作为一种有效的分割方法,被广泛应用于模式识别和图像处理中.传统的图像分割方法并不能获得足够有效的图像特征.为解决这个问题且进一步探究熵阈值在图像分割中的应用,引入一种GLLE(Gray Level and Local Entropy)二维直方图改进熵阈值图像分割模型,并提出了基于模糊熵的方法计算所建立的二维直方图模型.通过标准实验数据集上的对比实验表明,基于模糊熵的GLLE熵阈值分割方法可以得到更加准确的阈值,提高了分割精度.同时在处理不同类型图像的表现上优于往常的算法,具有更强的鲁棒性. 相似文献
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利用2007年8月8~9日陕西中部一次超强雷暴天气的闪电定位资料、 天气图、 多普勒雷达和卫星云图资料, 从动力学、 物理学等方面分析了此次强雷电天气产生的主要原因。结果表明: 远距离台风外围的低层偏东气流到达陕西中部, 增强了低层的水汽和能量, 对大暴雨和强雷电天气的产生起到了非常重要的作用; 中-α尺度对流云团发展期是产生高密度大强度雷电的主要时段, 雷电主要发生在TBB≤-60℃的云区; 产生强雷电的雷达回波强度达到50~60 dBz, 垂直液态水含量VIL为60~70 kg/m2, 云顶高度达到或超过15~17 km; 雷电的产生主要与对流云低层辐合区水汽通量的大小有关: 低层辐合区水汽通量比较小时, 有利于雷电的产生。 相似文献
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Tropical Cyclone Cloud Image Segmentation by the B-Spline Histogram with Multi-Scale Transforms
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An efficient tropical cyclone(TC) cloud image segmentation method is proposed by combining the curvelet transform,the cubic B-Spline curve,and the continuous wavelet transform.In order to enhance the global and local contrast of the original TC cloud image,a second-generation discrete curvelet transform is implemented for the original TC cloud image.Based on our prior work,the low frequency components are enhanced by using an incomplete Beta transform and the genetic algorithm in the curvelet domain. The... 相似文献
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2009年江苏一次强对流天气过程的遥感监测 总被引:4,自引:2,他引:2
以卫星水汽图为主,结合可见光云图、雷达资料和常规天气观测资料,分析2009年6月5日发生在江苏徐州沛县的一次冰雹、龙卷天气,结果表明:卫星水汽图中动力异常区与对流系统的交界处和可见光云图上两个对流云团出流边界处触发的新的雷暴云团区域容易产生龙卷等强对流天气;水汽图上的水汽输送带与可见光云图的对流云系相一致,并且水汽图像特征与导致垂直运动和气流变形场的大尺度天气过程有关系,代表着对流层中上部的动力特征;强对流天气发生在低亮温对流云团中。高时空分辨率的卫星和雷达遥感资料很好地反映了短时强对流天气系统的发展与演变,有效地补充了常规天气资料分析的不足,为短时天气预报提供一种思路。 相似文献
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Revisiting the size of nonspherical particles recorded by optical array probes with a new method based on the convex hull
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Rong Zhang Xu Zhou Hongyu Li Hanchao Li Lei Wei Yang Gao Qiang Xia Xiangyu Wang 《大气和海洋科学快报》2022,15(3):100136
In recent years, the Cloud Imaging Probe (CIP) and Precipitation Imaging Probe (PIP) produced by Droplet Measurement Technologies (DMT) have been introduced by a number of meteorological research and operation centers in China. The supporting software provided by DMT, i.e., PADS (Particle Analysis and Display System), cannot output detailed information on each individual particle, which definitely limits the in-depth utilization of cloud and precipitation particle image data in China. In this paper, particle-by-particle information was extracted by decompressing the CIP and PIP original particle image data, based on which a new definition of the dimension for nonspherical particles is proposed by using the area of the convex hull enclosing a particle to obtain the equivalent diameter of a circle with equal area. Based on the data detected during one flight in Inner Mongolia, the particle size distribution obtained using the new particle size definition and that used by the other four existing definitions are compared. The results show that the particle number concentration calculated using different particle size definitions can vary by up to an order of magnitude. The result obtained based on the new particle size definition is closest to that calculated with the area-equivalent diameter definition.摘要 国内许多气象部门已引进美国DMT公司的云粒子图像探头 (CIP) 和降水粒子图像探头 (PIP) . 由于其配套软件不能输出逐个粒子的详细信息, 在很大程度上限制了对云降水粒子图像探测数据的深入挖掘. 通过解析CIP和PIP原始数据, 提出了一种基于包围粒子凸多边形的面积求取粒子尺度的新定义. 利用在内蒙古的一次航测数据, 对比分析了基于新定义及已有的四种粒子尺度定义求取的粒子尺度谱分布. 相似文献
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低能见度是对道路通行影响最为严重的气象要素之一。随着数字摄像技术和图像识别技术的发展以及气象和交通部门间信息共享工作的开展,利用高速公路沿线摄像头视频数据快速识别能见度成为提高能见度时空监测精度的重要手段。本文提出了一种基于亮度对比度和暗原色先验原理的白天道路图像能见度检测方法。首先根据霍夫变换直线检测方法提取道路兴趣域,然后根据亮度对比度方法检测人眼可分辨最远像素点,将其作为目标点,最后基于暗原色先验原理求取目标点的透射率,并根据能见度与消光系数的关系公式求取图像能见度值。利用安徽省京台高速吴玗北段和宁绩高速宁国互通段视频图像资料和邻近交通气象站能见度监测资料,采用绝对误差和能见度等级误差对能见度检测效果进行检验。结果表明,本方法对能见度的变化较为敏感,能见度等级的检测效果较好,准确度可达95%,对开展公路交通视频图像能见度识别工作具有较好借鉴应用意义。 相似文献