共查询到14条相似文献，搜索用时 735 毫秒
1.
TRMM PR雷达与阜阳雷达降水资料的对比研究 总被引：8，自引：0，他引：8
选取了1998年与1999年HUBEX观测资料，将TRMM卫星上的星载降雨雷达PR与阜阳的713数字化天气雷达资料在以下3个方面做了比较：(1)强度场的分布；(2)平均反射率廓线；(3)灵敏度。分析、比较结果可知阜阳雷达在探测灵敏度和水平方向的分辨率要高于PR，但由于波束宽度、衰减和资料转化过程计算误差的原因，其远距离处的观测值与真实值有一定偏差。PR波长短，对衰减敏感，尤其是在垂直方向上经过强衰减后，订正值仍偏小。但由于探测方式的不同PR在水平方向上不存在衰减的问题，且其资料分布均匀，因此提出一种用PR资料来订正地基雷达资料的方法用以提高地基雷达探测的精确度。 相似文献
2.
3.
TRMM PR雷达与阜阳雷达降水资料的对比研究 总被引：1，自引：0，他引：1
选取了1998年与1999年HUBEX观测资料，将TRMM卫星上的星载降雨雷达PR与阜阳的713数字化天气雷达资料在以下3个方面做了比较：(1)强度场的分布；(2)平均反射率廓线；(3)灵敏度。分析、比较结果可知阜阳雷达在探测灵敏度和水平方向的分辨率要高于PR，但由于波束宽度、衰减和资料转化过程计算误差的原因，其远距离处的观测值与真实值有一定偏差。PR波长短，对衰减敏感，尤其是在垂直方向上经过强衰减后，订正值仍偏小。但由于探测方式的不同PR在水平方向上不存在衰减的问题，且其资料分布均匀，因此提出一种用PR 相似文献
4.
本文基于多幅TerraSAR卫星聚束模式SAR影像，研究了武汉特高压试验基地内特高压输电铁塔的雷达散射机制和干涉特性。利用高精度LiDAR扫描铁塔并进行三维建模，基于SAR几何成像关系分析了铁塔不同部位的散射几何关系。对比分析了基于散射强度和投影几何关系量测的铁塔横担间的高差，以及干涉图中相位变化反演的高差。结果表明相位推算的高差受噪声的干扰较大。本文对覆冰铁塔构件的雷达影像进行了理论分析和数据统计。结果表明，10 cm覆冰厚度破坏了铁塔构件二面角散射条件，造成雷达散射信号强度衰减了约8 dB，这表明输电铁塔雷达散射强度的变化可用于量化评估铁塔的覆冰状态。 相似文献
5.
小叶锦鸡儿是内蒙古灌丛化草原中最具代表性的景观植物，准确估算小叶锦鸡儿灌丛的地上生物量对研究灌丛化草原生态系统、监测草原灌丛化程度具有重要意义。地基激光雷达TLS(Terrestrial Laser Scanning)可通过获取高密度点云数据准确估算灌木体积，被广泛应用于反演灌木生物量，但在灌丛化草原中尚未得到有效应用。本研究首先在中国科学院灌丛化草地植被恢复试验区获取了5个样方(10 m×10 m)共42株灌丛的TLS点云数据及实测生物量信息；然后分别使用整体凸包法、切片凸包法、切片分割法、体积表面差分法、体素法5种方法计算灌丛体积并与实测生物量进行回归分析；最后，通过留一交叉验证对5种方法建立的生物量估算模型精度进行对比分析。结果表明：TLS可在不破坏植被的情况下实现快速、准确地小叶锦鸡儿灌丛生物量反演，是传统野外调查方法的可靠替代技术。研究中采用的5种方法均能较好地估算灌丛生物量，其中：（1）相比于整体凸包法（R 2=0.87, p<0.001, RMSE=30.50 g），切片凸包法（R 2=0.89, p<0.001, RMSE=28.01 g）与切片分割法（R 2=0.88, p<0.001, RMSE=29.03 g）可有效减弱离群点造成的体积高估，生物量估算精度有所提升；（2）格网大小为3 cm、高度统计变量选取标准差时，体积表面差分法计算的体积与实测生物量拟合度最好(R 2=0.89, p<0.001, RMSE=28.89 g)，表明高度标准差是估算小叶锦鸡儿灌丛生物量的强预测因子；（3）体素法解释了生物量估计值90%的变化(R 2=0.90, p<0.001, RMSE=26.28 g)，是适合小叶锦鸡儿灌丛生物量反演的最优模型。 相似文献
6.
2016-09-15随天宫二号空间实验室发射升空的三维成像微波高度计（简称天宫二号成像高度计）是国际上第一个采用小入射角、短干涉基线实现宽刈幅海面高度测量的高度计。由于天宫二号没有为成像高度计配备用于大气校正的微波辐射计，因此需要采用模型方法对大气时延进行精确估计。传统高度计采用星下点观测，通常只考虑大气折射率的改变引起传播速度变化的时延。天宫二号成像高度计采用偏离星下点1°—8°的小角度观测，因此在进行大气传输时延校正时不仅要考虑雷达信号传播速度的改变，还应考虑由于传播方向改变带来的路径弯曲效应。本文针对天宫二号成像高度计的观测几何特性，提出基于数值天气模型校正大气斜距时延的算法：采用欧洲中期天气预报中心的天气数据和大气分层模型，通过气象参数计算大气折射率；根据高度计参数和各层大气折射率，依赖折射定律和信号传播的几何关系在路径上逐层积分，计算大气斜距时延的估值。通过对天宫二号成像高度计的陆地角反射器定标实测数据进行处理，经大气斜距时延校正后，角反射器的剩余距离误差的标准差约为6.2 cm，达到厘米量级的斜距测量精度，验证了在不同入射角情况下，所提出的大气斜距时延校正算法的有效性和可靠性。 相似文献
7.
An operational radar rainfall estimation system based on the adaptive radial basis function (RBF) neural network is developed. During the process of training and cross validation, the rainfall estimation was computed only at the gauge locations. Once the training is done, the radar rainfall estimation based on neural networks is applied to the full coverage area of the radar. Such large-scale application of the rainfall estimate poses several questions in the context of operational applications. This letter addresses two of those questions, namely: 1) the feasibility of adaptively updating RBF neural network models on a daily basis and 2) the ability of neural network radar rainfall estimation at high spatial resolution within reasonable and practical time frame for operational applications. Using the datasets collected by WSR-88D radar located in Melbourne, FL, it is demonstrated that radar-based rainfall estimation using an adaptive RBF neural network is feasible. The results show that 73% of overnight updating for the RBF neural network can be completed within 2 h, and the estimation over an area of 100 km/spl times/100 km can be generated within the time frame (a few tens of seconds-150 s), which is much smaller than the average radar volume scan time. 相似文献
8.
Anagnostou M.N. Anagnostou E.N. Vivekanandan J. Ogden F.L. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(4):601-605
This letter evaluates the consistency of rainfall drop size distribution (DSD) parameters that were estimated from attenuation-corrected X-band dual-polarization (XPOL) radar measurements with estimates from a colocated S-band dual-polarization radar (S-Pol). The DSD retrieval technique uses reflectivity and differential reflectivity, and a constrained relationship to estimate the three parameters of a ldquonormalizedrdquo gamma distribution model. The more definitive S-Pol DSD parameter estimates are used as a reference to assess the performance of the corresponding XPOL estimates for different rain-path attenuation values. Results show that XPOL attenuation-corrected profiles can provide rainfall DSD estimations that are consistent to an S-band dual-polarization radar, even in cases of moderate to high rain-path attenuation. 相似文献
9.
“凤凰”台风期间海面风、浪的高频地波雷达OSMAR071遥感 总被引：1，自引：0，他引：1
介绍了OSMAR071高频地波雷达系统“凤凰”台风期间海面风、浪遥测结果。文中给出高频地波雷达OSMAR071 风、浪反演算法：利用SBM模型结合多波束采样法反演风向;利用改进的Barrick模型进行有效波高的反演;利用SMB关系式进行风速反演。将雷达定点观测结果与浮标数据进行对比,表现出很好的一致性,其中有效波高相关系数为0.72,均方根误差为0.48 m,风向相关系数为0.97,均方根误差为27.7°,风速的相关系数为0.6,均方根误差为 3.5 m/s。文中还对影响探测精度的因素进行了分析。 相似文献
10.
合成孔径高度计的海面回波仿真 总被引：1，自引：0，他引：1
本文首先采用经验海浪谱仿真了三维海面,进而在此基础上根据镜面反射理论计算了海面小面元散射系数。然后根据雷达方程和合成孔径高度计的合成孔径处理计算了海面回波信号的矩阵,以便给出最终的功率回波。在目前国内外缺少相应试验数据的条件下,验证了合成孔径高度计工作方式的有效性,经验证其回波模型基本正确。同时,为了与传统高度计比较,给出了传统高度计在相同参数下的回波仿真结果。文章还通过展示合成孔径高度计在同种波高、不同涌浪和风浪方向情况下的回波,说明波浪方向也会影响合成孔径高度计回波。 相似文献
11.
This is the second letter of the series on improving operational measurement of precipitation using radar in mountainous terrain. Four major rainfall events (11 days) that affected the Western Alps between autumn 1994 and autumn 2000 are analyzed. In the first letter, the focus was on the advantages/disadvantages of the adjustment techniques, the importance of the training, and quality check of the radar-gauge couples used for the training itself. In this letter, our objective is to verify the improvement that can be eventually be obtained by applying in real time the adjustment techniques previously described. The first day of each event was used in the training, and the remaining seven days provided the dataset for the verification (up to 70 gauges in a /spl sim/12000-km/sup 2/ area within 157 km from the radar). A simple bulk adjustment is able to reduce the root-mean-square differences between the daily radar and gauge amounts. A further improvement can be obtained by using, instead of a single bulk-adjusted coefficient, the four correction coefficients derived through a weighted multiple regression (WMR). Thanks to the four WMR-derived coefficients, it is possible to correct several errors in one step (not only "bias," but also beam-broadening, shielding, and orographic enhancement). As a consequence, it represents an inexpensive alternative to more sophisticated methods (e.g., vertical reflectivity profile correction), and at least during intense "long-lasting" (one day or more) events, it could be used operationally to improve-in real time-precipitation estimates over mountainous terrain. 相似文献
12.
建立双基地SAR的单基地等效模型,分析了系统时间同步误差的机理;提出了双基地SAR回波中的直达波数据进行时间同步误差校正的算法;在双基地SAR单站等效模型的基础上,利用时变阶梯变换算法进行成像处理。经过理论分析,实测数据处理验证,这一算法是有效的,能够校正双基地SAR时间同步误差,较好地进行实测数据的成像处理。 相似文献
13.
The Spaceborne Laser Ranging System is a proposed short pulse laser on board an orbiting spacecraft.1,2,3,4 It measures the distance between the spacecraft and many laser retroreflectors (targets) deployed on the Earth’s surface.
The precision of these range measurements is assumed to be about ±2 cm (M. W. Fitzmaurice, private communication). These measurements are then used together with the orbital dynamics of the spacecraft, to derive
the relative position of the laser ground targets. Assuming a six day observing period with 50% cloud cover, uncertainties
in the baseline for target separations of 50 km to 1200 km were estimated to be on the order of 1 to 3 cm and the corresponding
values in the vertical direction, ranged from 1 cm to 12 cm. By redetermining the measurements of the relative target positions,
the estimated precision in the baseline for a target separation of 50 km is less than 0.3 cm and for a separation of 1200
km is less than 1 cm. In the vertical direction, the estimated precision ranged from 0.4 cm to 4.0 cm respectively. As a result
of the repeated estimation of the relative laser target positions, most of the non-temporal effects of error sources as exemplified
by the errors in geopotential are reduced.
The Spaceborne Laser Ranging System’s capability of determining baselines to a high degree of precision provides a measure
of strain and strain rate as shown byCohen, 1979. These quantities are essential for crustal dynamic studies which include determination and monitoring of strain near
seismic zones, land subsidence, and edifice building preceding volcanic eruptions. It is evident that such a system can also
be used for geodetic surveys where such precisions are more than adquate. 相似文献
14.
针对海面舰船等具有一定空间稀疏性的合成孔径雷达成像场景,提出了一种稀疏场景目标的距离像峰值聚类分割成像方法。首先采用小波降噪算法对SAR原始回波数据进行预处理,通过距离压缩和距离徙动校正获得不同观测位置的距离像,利用基于二阶差分算子的快速峰值检测算法检测距离像峰值点,对峰值检测结果距离维聚类后方位向成像,实现了距离向能量区间稀疏目标的分割成像;对峰值检测结果距离-方位二维聚类后方位向成像,实现了距离向能量区间与方位向合成孔径时间无耦合稀疏目标的分割成像。仿真结果表明,对海面舰船等具有空间稀疏性的成像场景,所提方法能够实现目标的有效分割成像,不仅在完整保留目标回波信息的同时大幅度地降低了方位向压缩的运算量,而且分割成像结果更有利于目标的快速识别。 相似文献