共查询到14条相似文献,搜索用时 546 毫秒
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浪向代表着海浪传播方向,它是海上交通安全以及海岸资源管理的重要海洋环境参数之一。本文针对X波段测波雷达对海杂波的连续成像,提出了一种基于光流法的海浪传播方向反演新方法。该方法利用X波段测波雷达接收的海面回波图像序列直接进行光流运动估计,将得到的每个像素点的运动矢量进行加权平均,最后得到实际的海浪传播方向。与传统基于频域的X波段测波雷达浪向反演方法相比,本文提出的方法直接从时域来进行回波信号处理,无需提前得到调制传递函数以及精确的海流,减少了由于海流估算的不准确以及调制传递函数选取的误差而给雷达浪向反演带来的影响。同时,该方法简单高效,占用资源少,将其应用至仿真雷达回波以及现场实测数据来进行浪向反演,反演得到的浪向与仿真设定浪向值以及浮标实时观测浪向结果都有很好的吻合度,变化趋势也完全一致,进而验证了该方法的有效性以及准确性。 相似文献
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船用X波段雷达被广泛应用于海洋表面波观测和研究。本文给出了一种新的从船用X波段雷达图像中确定主波传播方向的方法。X波段雷达图像中的海浪信号具有明显的尺度性和方向性。同时,curvelet变换作为一种同时具备尺度分辨率和方向分辨率的数学变换,能够对一幅雷达图像在不同尺度、不同方向和不同位置上进行分析。对一幅雷达图像进行curvelet分解并获得curvelet系数后,波浪信号主要集中在某些特定尺度和方向的curvelet系数中,从而我们可以获得带有 方向模糊的波传播方向。进而,通过计算几幅连续采集图像的互相关系数可以消除 方向模糊。同步观测的雷达图像和浮标数据证明了该方法的有效性。 相似文献
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X-波段雷达近海海浪频谱反演的神经网络模型 总被引:2,自引:1,他引:1
X-波段雷达作为国内海浪观测的一种新工具,在海浪频谱获取和有效波高反演方面仍存在较多问题.本文利用非线性回归方法,将现场实测浮标数据频谱和雷达一维图像谱分别与标准频谱模型进行拟合,发现浮标频谱和一维图像谱具有标准频谱的特征,能够较准确地获取相应的谱参数.提出了建立由雷达一维图像谱参数反演海浪频谱参数的神经网络模型,同时在模型中加入影像序列信噪比,进而反演有效波高,并将反演结果与现场实测数据和传统算法(建立影像序列信噪比与有效波高之间的线性回归方程)进行了对比,结果表明,获取谱参数的误差和反演有效波高的平均误差在20%以内,而传统算法计算有效波高平均误差在20%以上. 相似文献
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船用X波段导航雷达凹波形成的海杂波图像中包含丰富的海浪、海表层流信息.借鉴合成孔径雷达(SAR)估计有效波高的方法,假设有效波高与雷达回波强度信噪比的平方根成线性关系,可由X波段雷达图像估计得到海浪的有效波高.用此方法主要分析小麦岛海域实验数据,结果显示,直流滤波后计算的信噪比估计的有效波高比不进行直流滤波结果符合得好;而按波浪浮标测得有效波高数据的高低,分两段分别进行线性拟合获取校准系数,估测的有效波高更加准确. 相似文献
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降雨条件下的导航X波段雷达海浪参数反演算法研究 总被引:1,自引:0,他引:1
X波段的电磁波受降雨影响容易产生衰减,这导致导航X波段雷达在降雨时无法用于海浪观测。本文提出了一种新的降低降雨影响的算法来反演海浪参数。首先,对X波段雷达图像做主成分分析,获得波浪变化的主成分,利用一维傅里叶变换得到波数谱,对其滤波减小降雨对雷达图像的影响;然后,选取JONSWAP(Joint North Sea Wave Project)谱作为理论谱,建立以观测谱与理论谱的最小化差异为目标函数的模型,求解该模型估算海浪的有效波高。与浮标测量的有效波高相比,该方法反演的有效波高的均方根误差是0.23 m,证明了该方法的可行性。 相似文献
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近年来,X波段雷达已经成为重要的海洋现场观测设备,应用越来越广泛,但其在复杂天气条件下的观测准确性还需要进一步探讨。因此,为了验证X波段测波雷达对于海洋波浪的观测性能,对安装于我国三亚市三亚湾的X波段雷达设备及布放在该区域的波高仪进行了海浪比测试验,通过对压力测波与X波段雷达测波两种不同探测机制在不同海况下实际海浪观测数据结果的分析可以得出:X波段雷达对于海浪观测的结果较为理想,与压力测波结果相关性较高,在不同天气条件下,均能够准确地反演大范围海域的海浪信息。根据研究结果,X波段雷达的波浪现场观测数据完全可以达到海洋环境监测的要求。 相似文献
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基于理论的气旋条件下双极化C波段合成孔径雷达波参数检测 总被引:2,自引:1,他引:1
Theoretical-based ocean wave retrieval algorithms are applied by inverting a synthetic aperture radar(SAR)intensity spectrum into a wave spectrum, that has been developed based on a SAR wave mapping mechanism. In our previous studies, it was shown that the wave retrieval algorithm, named the parameterized first-guess spectrum method(PFSM), works for C-band and X-band SAR at low to moderate sea states. In this work, we investigate the performance of the PFSM algorithm when it is applied for dual-polarization c-band sentinel-1(S-1) SAR acquired in extra wide-swath(EW) and interferometric wide-swath(IW) mode under cyclonic conditions.Strong winds are retrieved from six vertical-horizontal(VH) polarization S-1 SAR images using the c-band crosspolarization coupled-parameters ocean(C-3 PO) model and then wave parameters are obtained from the image at the vertical-vertical(VV) polarization channel. significant wave height(SWH) and mean wave period(MWP) are compared with simulations from the WAVEWATCH-III(WW3) model. The validation shows a 0.69 m root mean square error(RMSE) of SWH with a –0.01 m bias and a 0.62 s RMSE of MWP with a –0.17 s bias. Although the PFSM algorithm relies on a good quality SAR spectrum, this study confirms the applicability for wave retrieval from an S-1 SAR image. Moreover, it is found that the retrieved results have less accuracy on the right sector of cyclone eyes where swell directly affects strong wind-sea, while the PFSM algorithm works well on the left and rear sectors of cyclone eyes where the interaction of wind-sea and swell is relatively poor. 相似文献
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The velocity and direction of internal waves (IWs) are important parameters of the ocean, however, traditional observation methods can only obtain the average parameters of IWs for a single location or large area. Herein, a new method based on optical flow is proposed to derive the phase velocity vectors of IWs from X-band marine radar images. First, the X-band marine radar image sequence is averaged, and ramp correction is used to reduce the attenuation of gray values with increasing radial range. Second, the average propagation direction of the IWs is determined using the two-dimensional Fourier transform of the radar images; two radial profiles along this direction are selected from two adjacent radar images; and then, the average phase velocity of the IWs is estimated from these radial profiles. Third, the averaged radar images are processed via histogram equalization and binarization to reduce the influence of noise on the radar images. Fourth, a weighting factor is determined using the average phase velocity of a reference point; the phase velocities on the wave crest of the IWs are subsequently estimated via the optical flow method. Finally, the proposed method is validated using X-band marine radar image sequences observed on an oil platform in the South China Sea, and the error of the phase velocity is calculated to be 0.000 3–0.073 8 m/s. The application conditions of the proposed method are also discussed using two different types of IW packets. 相似文献
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《Oceanic Engineering, IEEE Journal of》2005,30(3):534-542
This paper describes two algorithms for the retrieval of high-resolution wind and wave fields from radar-image sequences acquired by a marine X-band radar. The wind-field retrieval algorithm consists of two parts. In the first part, wind directions are extracted from wind-induced streaks, which are approximately in line with the mean surface wind direction. The methodology is based on the retrieval of local gradients from the mean radar backscatter image and assumes the surface wind direction to be oriented normal to the local gradient. In the second part, wind speeds are derived from the mean radar cross section. Therefore, the dependence of the radar backscatter on the wind vector and imaging geometry has to be determined. Such a relationship is developed by using neural networks (NNs). For the verification of the algorithm, wind directions and speeds from nearly 3300 radar-image sequences are compared to in situ data from a colocated wind sensor. The wave retrieval algorithm is based on a methodology that, for the first time, enables the inversion of marine radar-image sequences to an elevation-map time series of the ocean surface without prior calibration of the acquisition system, and therefore, independent of external sensors. The retrieved ocean-surface elevation maps are validated by comparison of the resulting radar-derived significant wave heights, with the significant wave heights acquired from three colocated in situ sensors. It is shown that the accuracy of the radar-retrieved significant wave height is consistent with the accuracy of the in situ sensors. 相似文献