共查询到20条相似文献，搜索用时 31 毫秒
1.
Emad Ghaleh Noei Mahdi Hasanlou Mohammad Ali Sharifi 《Journal of the Indian Society of Remote Sensing》2018,46(12):2093-2106
Seafloor topography certainly has an impact on ocean circulation in different ways. Due to this assumption, the sea surface currents calculated by optical flow (Horn–Schunck) and geostrophic currents methods are analyzed to observe this impact. Pair of sea surface temperature imageries, calculated sea surface height and sea level anomaly are showed beside depth map in areas with meaningful bathymetric features such as underwater mountains and pools. The reason for the formation of some eddies in the Caspian Sea and Indian Ocean is concluded from the location of pools and knolls. In this study, in addition to introducing new time span for calculating geostrophic currents, Ocean Surface Current Analyses Real-Time (OSCAR) currents are applied to validate our estimated currents. Variety of products such as sea surface temperature imageries, OSCAR currents, depth map, calculated results like sea level anomaly and absolute dynamic topography and estimated currents via optical flow and geostrophic currents have been collected in this paper to make very detailed investigation on depth effect on mentioned water parameters. Results show that impacts of knolls and pools are meaningfully clear in optical flow and geostrophic currents in shaping and rationing water motions. 相似文献
2.
基于已知定向参数影像的光束法区域网平差 总被引：1，自引：1，他引：1
从自检校光束法区域网平差模型出发,建立了利用同一地区已知定向参数的影像解求新获取影像外方位元素并进行目标定位的数学模型。以此为基础,对来自某地区相隔两年的三期不同摄影比例尺航空影像两两组合地进行联合光束法区域网平差。结果表明,当两期影像比例尺相近时,所解求的新影像外方位元素和加密点坐标精度基本达到常规光束法区域网平差的精度;当两期影像比例尺不同时,利用已知定向参数的大比例尺影像解求出的小比例尺影像的外方位元素和加密点坐标可满足现行规范精度要求,利用已知定向参数的小比例尺影像去解求大比例尺影像的外方位元素和加密点坐标精度明显下降且不可用。本文的研究证实,就同一地区的多时相航摄影像而言,利用已知定向参数的影像进行新影像的定向方法是可行的。 相似文献
3.
本文利用傅立叶波形分析算法处理了光谱反射率数据,把不同地物的光谱分解为特征意义明确,信息内涵丰富,对各种地物可分辨性强的各次谐波分量。诸谐波分量的参数——波幅和初相唯一地决定了其对光谱曲线的贡献和构形位置。试验表明傅立叶波形分析算法可以成为处理各种成像光谱仪获取的超维图像的有效工具。 相似文献
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我国东部某地油气微渗漏的遥感研究 总被引：2，自引：0，他引：2
我国东部某地一些油气田区的遥感图像(本文为国土卫星彩红外片)上,常见有一些灰白色、浅褐色云雾状色调异常,经过地植物、土壤的地面光谱测试和土壤气体化探检查,发现色调；异常范围内、外植物和土壤光谱存在一定差异,异常内还发现有烃类气体异常,这种色调异常极有可能与油气微渗漏有关。对这种遥感图像上的色调异常进行的计算机增强处理研究表明,正规化与频谱变量、时间变量标准化交换组合处理效果较好,处理后的图像上色调异常显示十分明显。据永安地区国土卫星彩红外片正规化、标准化组合处理图像上显示的色调异常与已知油气田十分吻合,说明该处理方法是有效的。 相似文献
6.
Maged Marghany 《Journal of the Indian Society of Remote Sensing》2004,32(2):185-198
This paper presents the application of the velocity bunching model to detect the wave spectra pattern. We have developed the
azimuth cut-off model which is estimated from the velocity bunching theory to model out the significant wave height. The velocity
bunching model utilized two ERS-1 images (First European Remote Sensing Satellite). These two ERS-1 images have been acquired
with the different monsoon periods. Several steps have been used to simulate the significant wave height from the velocity
bunching model, these were: the real ocean wave spectra simulated from the in situ wave data, and the SAR wave spectra, extracted
by applying two-dimensional Fourier transform (2-DFFT). Finally, the significant wave height was estimated based on the azimuth
cut-off arising from the velocity bunching model. Two hypotheses were established in modelling the wave spectra from the SAR
images: (i) azimuth cut-off was based on velocity bunching, which has been used to model the significant wave height with
high accuracy, and (ii) velocity bunching model has been used to map the SAR wave spectra into ocean wave spectra. In the
present study, a specific ERS-1 images of the South China Sea has been considered. No significant differences were found between
the velocity-bunching model and ocean wave spectra model where ERS-1 wave spectra has been found to be dominated by the azimuth
fall-off effects. Furthermore, the velocity bunching model produced wave spectra pattern approximately closed to the real
ocean wave compared to the SAR wave spectra. The highest rate of r2 (0.69) occurred when the significant wave height increased. It has been concluded that the velocity bunching model could
be used as the best fit model for estimating the significant wave height traveled along the azimuth direction. 相似文献
7.
由于人类识别图像特征涉及非线性的识别机制,本文提出了基于改进二维Log Butterworth滤波器的全方向边缘检测方法,该方法从频域角度出发,利用正反快速傅里叶变换来实现边缘检测工作。首先,将非线性Log函数引入Butterworth滤波器,获得二维Log Butterworth滤波器。当图像行列数不一致时,中心频率分布于椭圆之上,椭圆的长短轴之比与图像长宽比相等,进而给出以角度为变量滤波器表达式;其次,为方便滤波器参数的优化选取,本文对二维 Log Butterworth滤波器参数进行归一化等处理;再次,本文利用F-measure和PSNR (峰值信噪比)值来衡量不同参数下的边缘检测结果,确定最优的二维 Log Butterworth滤波器参数范围;然后,为了分析本文方法的边缘检测效率,对比了本文方法与空域算子（Canny算子）的乘法次数和加法次数,同时以不同大小的图像作为实验数据来比较两种方法的边缘检测耗时;最后,以BSDS（伯克利图像分割数据库）图像和高空间分辨率遥感图像为实验数据,对本文方法的边缘检测结果进行了评价分析。结果表明：本文方法可以有效地应用于图像边缘检测。 相似文献
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Abstract Landsat MSS, TM and SPOT XS imageries were used in conjunction with unsupervised, supervised and hybrid classilication techniques to classify land cover types in semi‐arid savannas of Mathison Pastoral Station in the Katherine region of northern Australia. Accuracy assessment was based on field data from 246 ground survey sites over a 745‐km2 study area. Of 14 land cover classes identified by traditional mapping means, all combinations of imageries and classification techniques differentiated at least seven land cover types. The overall accuracy for these classifications ranged between 43% and 67%. SPOT XS image delivered the best accuracy followed by TM and MSS; unsupervised classification performed better than supervised and hybrid methods. User's and producer's accuracy of individual land units ranged from 0% to 100%. Riparian woodlands, woodland on limestone slopes, shrubland on clay plains, woodland on limestone plains and shadows were the best‐mapped classes. The land units that were associated with undulating hills were not mapped accurately. However, incorporation of a digital elevation model (DEM) in a GIS improved the overall accuracy. The user's and producer's accuracy of dominant land cover types were also enhanced. The classification results and the efficacy of the techniques at Mathison were similar to those found for a nearby semi‐arid area (Kidman Springs) about 200 km from Mathison. However, the overall accuracy was lower at Mathison than at Kidman Springs. Spectral classification masks were developed from the SPOT XS and TM imageries at Kidman Springs, and were applied to classify SPOT XS and TM imageries at Mathison. Initial results showed that the classification mask could be successfully extrapolated to map dominant land cover types but only with moderate accuracy (50%). 相似文献
9.
A. A. Fernandes Y. V. B. Sarma H. B. Menon P. Vethamony 《Journal of the Indian Society of Remote Sensing》2000,28(1):9-18
Gaussian smoothed SAR image spectra have been evaluated from 512 x 512 pixel subscenes of image mode ERS-1 SAR scenes off Goa, Visakhapatnam, Paradeep and Portugal. The two recently acquired scenes off Portugal showed the signature of swell of wavelength ≈ 200m and internal waves of wavelength > 400m. Only internal waves of wavelength > 400m were seen in the scene off Goa observed on 11 March 1992. The scenes off Visakhapatnam and Paradeep did not show any wave like features, the latter appearing to be of “white noise” nature. There exists a 180° ambiguity in wave direction observed from radar imageries. Based on the method of Atanassov et al (1985), a computer program has been developed for the removal of the 180° ambiguity by using two images of the same area separated by a time interval which is small compared to the period of the dominant waves. The computer program has been successfully tested with computer simulated images. 相似文献
10.
地形校正是准确获取地形复杂区遥感反射率的重要步骤，对提高山区地表遥感参数定量化反演精度，扩大遥感产品应用广度具有重要意义。从20世纪80年代开始，国内外学者开始对准确获取山区地表遥感反射率进行研究，建立了多种地形校正模型来减少或消除遥感图像中地形效应影响，减少同种地表类型的反射率差异，并将地形校正模型分为经验模型和物理模型。根据构建物理模型时是否考虑地表非朗伯体特性，将物理模型分为朗伯体假设模型和非朗伯体假设模型，本文分别从朗伯体假设模型和非朗伯体假设校正模型展开叙述。从两类模型构建的理论基础，模型特点，局限性等几方面进行分析和讨论，描述了两类模型的发展历程，系统阐述了朗伯体假设模型和非朗伯体假设模型的适用性和不足，剖析了目前地形校正模型存在的问题与挑战。同时，本文也比较了应用于地形校正的效果评价方法，并展望了地形校正方法和地形校正评价方法的未来主要发展方向。 相似文献
11.
Maneesha Gupta Anuja Sharma B. Kartikeyan 《Journal of the Indian Society of Remote Sensing》2017,45(2):195-207
The single-frequency Radar Imaging Satellite-1 (RISAT-1) Synthetic Aperture Radar (SAR) (launched in April, 2012) is designed to provide a wide variety of imaging options compared to the prevailing SAR missions. The scale of the calibration task for the RISAT-1 mission is increased with the inclusion of multiple beams and polarizations (single, dual and quad) along with circular/hybrid polarization capabilities, for the first time from space. Significant efforts have been made in the evolution of SAR processor for the provision of radiometrically and geometrically calibrated products to the users. After the commissioning phase, RISAT-1 was put into routine operations in Oct. 2012. Since then extensive beam coverage of Amazon rainforest in various modes was carried out to evaluate the calibration parameters and SAR processor performance. Subsequently, the processor version 1.2.0 was improved to version 1.3.0 and with further modifications to version 1.4.0. This article details the analysis carried out at each processor version, by quality evaluation team, to quantify the parameter behaviour and to give feedback on the processor performance to the SAR processor team. The various radiometric quality parameters evaluated and monitored are shape of the antenna pattern, gamma-naught, backscattering coefficient (sigma-naught), speckle index, radiometric resolution and Noise Equivalent Sigma Zero (NESZ). Data studied for the analysis is in Single Look Complex (SLC) for stripmap mode and multilook (Ground range) for ScanSAR and stripmap mode in dual and circular polarizations. The performance of version 1.4.0 for all the beams (near-to-far) is found to be consistent and meeting the mission specifications for the product. 相似文献
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A new method for semi-automatic identification of oil slick on ocean/sea surface from space borne imagery using optical power spectra has been suggested. This method is based on the fact that the presence of the oil slick in the ocean suppresses the normal wave pattern that will be present in the ocean area without oil slick and the power spectra of the image area having the oil slick will be devoid of the peak corresponding to the dominant wave. In addition, the general shape of the oil slick will increase the low frequency content in the power spectra. The method has been applied for test areas containing oil slicks and the results are encouraging. 相似文献
13.
Jia Liu Dustin Feld Jochen Garcke Thomas Soddemann Peiyuan Pan 《International Journal of Digital Earth》2016,9(8):748-765
Quantitative remote sensing retrieval algorithms help understanding the dynamic aspects of Digital Earth. However, the Big Data and complex models in Digital Earth pose grand challenges for computation infrastructures. In this article, taking the aerosol optical depth (AOD) retrieval as a study case, we exploit parallel computing methods for high efficient geophysical parameter retrieval. We present an efficient geocomputation workflow for the AOD calculation from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. According to their individual potential for parallelization, several procedures were adapted and implemented for a successful parallel execution on multi-core processors and Graphics Processing Units (GPUs). The benchmarks in this paper validate the high parallel performance of the retrieval workflow with speedups of up to 5.x on a multi-core processor with 8 threads and 43.x on a GPU. To specifically address the time-consuming model retrieval part, hybrid parallel patterns which combine the multi-core processor’s and the GPU’s compute power were implemented with static and dynamic workload distributions and evaluated on two systems with different CPU–GPU configurations. It is shown that only the dynamic hybrid implementation leads to a greatly enhanced overall exploitation of the heterogeneous hardware environment in varying circumstances. 相似文献
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随着地理信息和遥感技术的不断发展,高分辨率遥感影像的应用范围不断扩大,这对海量遥感影像的有效使用和管理提出了迫切需求。本文基于瓦片技术,对高分辨率遥感影像进行处理,实现了影像的快速访问。该技术已经应用到实际的测绘生产中,对提高生产效率和影像的统一管理具有重要意义。 相似文献
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基于FFT的快速SAR分布目标回波模拟算法 总被引：10，自引：0，他引：10
大面积分布目标的合成孔径雷达 (SAR)回波模拟需要大量的运算 ,文中提出了一种合成孔径雷达回波模拟的快速算法 ,算法利用时域插值和FFT来缩减运算量 ,对于大面积目标回波模拟时 ,该算法有很高的效率。文中详细分析sinc函数插值所带来的误差以及补偿方法 ,并在次基础上提出了一种利用增采样插值方法 ,该方法以增加少量运算为代价 ,使得模拟精度的大幅度提高。文中比较了传统方法和基于FFT的快速SAR分布目标回波模拟算法的模拟结果 ,证明了这种快速算法确实行之有效 相似文献
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基于正交变换的多通道遥感影像变化检测 总被引：3，自引：0，他引：3
针对多时相多通道遥感影像的变化检测问题，引入了多元统计中的典型相关分析方法，对遥感影像进行典型变换，并采用最小噪声比率变换对典型变换结果作后处理，得到差异影像，初步解决了将变化信息集中到少数分量中的问题。实验证实了该方法的有效性，并与主成分分析方法进行了比较。 相似文献
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大量城市建筑使得高分影像中含有许多阴影区。这些阴影区在土地利用分类、植被绿度调查等遥感应用中会较大地影响结果精度,降低数据使用效率并增加研究成本。基于同一地物阴影区与临近非阴影区反射率相等这一辐射特征关系,通过建立辐射传输方程,发展了一种新的城市高分遥感影像阴影校正方法 RERB(Reflectance Equality Relationship Based Method)。利用RERB对不同城市(北京和荷兰Enschede)不同高分多光谱影像(Geo Eye-1和Quick Bird)进行阴影校正,并对比分析其与被广泛采用的均值方差变换法MVT(Mean and Variance Transformation)的校正结果,通过定性和定量精度评价发现:(1)RERB能很好地将城市阴影区影像视觉特征(颜色、纹理、色调等)信息恢复到与非阴影区同一水平上;(2)RERB恢复后的阴影区具有丰富的细节信息且在视觉上与临近非阴影区具有良好的一致性;(3)RERB恢复后的城市柏油路面和水泥路面阴影区辐射信息具有较低的误差,可见光-近红外波段的平均误差分别为7%和9%。同时RERB能较好地恢复城市阴影区植被波谱特征信息。 相似文献
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遥感及其地球表面时空多变要素的区域尺度转换 总被引：16，自引：2，他引：16
阐明了遥感在获取时空多变要素中的作用和意义,同时利用遥感方法作出了空间变异较大的叶面积指数、地表温度和净辐射通量的区域分布。通过遥感方法与传统的区域表达方法的对比,讨论了传统的等值线方法及其区域要素计算和表达方法的不足,估算了利用空间差异较大的非均匀要素所作出的区域分布的可能误差。其步骤是： ①用遥感和生态网络观测数据相结合的方法作出几个要素的区域分布影像图; ②在影像图上标出单点生态站的观测数据; ③以图像处理的方法,作出不同范围的各种要素平均值和标准差; ④揭示单点站的观测数据和不同范围要素平均值的差异; ⑤分析用传统的等值线方法所作出的区域分布的可能误差。 相似文献
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The RPC model has recently raised considerable interest in the photogrammetry and remote sensing community. The RPC is a generalized sensor model that is capable of achieving high approximation accuracy. Unfortunately, the computation of the parameters of RPC model is subject to the initial of the parameter in all available liteature. An algorithm for computation of parameters of RPC model without initial value is presented and tested on SPOT-5, CBERS-2, ERS-1 imageries. RPC model is suitable for both push-broom and SAR imagery. 相似文献