秒级探空数据随机误差评估

利用2007年6月和2008年6—7月国内GPS探空仪同步比对试验数据及2010年中国阳江国际探空系统比对试验数据,基于现有的探空仪随机误差的间接计算方法,深入分析不同的探空原始数据平滑处理程度对随机误差评估的影响。分析表明:现有的探空仪随机误差评估方法不能完全适用于秒级探空数据,特别是对风、平流层温度和对流层相对湿度这3个要素的随机误差的评估。在同步比对施放中,如果对探空原始数据的平滑处理程度一致,可以利用现有的随机误差评估方法,不会产生明显偏差;反之,如果平滑处理程度差异较大,则间接计算得出的随机误差会明显偏大。在比对施放方案中,为了更好地获取某种型号探空仪的随机误差,建议将多个同型号探空仪同球施放进行比对观测,避免作为参考仪器的其他型号探空仪自身的误差参与计算,影响待测探空仪随机误差的评估。同型号探空仪同球施放的探空仪越多,获取的有效统计数据越多,随机误差的分析越准确。     

基于多面函数模型的GPS高程拟合精度分析

选择不同的拟合方法与拟合模型对GPS高程拟合精度有很大影响。本文研究了多面函数拟合模型中平滑系数选择对GPS拟合高程精度的影响。通过实例计算分析表明,选择不同的平滑系数,GPS高程拟合精度相差较大,在利用多面函数拟合GPS高程实践中应慎重选择平滑系数。     

基于可靠地估计反射方位和边界的构造约束保边滤波(英文)

本文给出一种既能有效衰减地震噪音又可保护地层及构造的不连续性的新方法。构造约束保边平滑技术需要已知反射局部方位和边界信息,通常这些信息由全频率地震资料估算获得,但在资料信噪比很低的情况下,噪音往往会降低估算的可靠度。对于信噪比极低的地震资料,其主频成分相对非主频成分信噪比高,所以由主频资料获取的方位和边界信息比由其它频率成分获取的更可靠。方位和边界信息通常用倾角和相干值差异来描述。由于不同频率所引起的倾角和相干值差异的变化均比地震记录的变化缓慢,所以由主频资料获取的倾角及边界信息能够近似代表所有频率成分的倾角及边界信息。Ricker子波广泛用于地震勘探,Marr小波与Ricker子波在时间和频率域均具有相同的形态,所以选用Marrl小波变换将地震数据按照倍频程分为几个分频体。扫描主频分频体,用不等权二次曲面拟合并求解极大值来获取视倾角,通过比较9个滑动窗口的相干值来确定反射边界。将这些信息用构造约束保边平滑技术可选择性地（selectively）对主频、低频、高频分频体做平滑处理,最后将平滑后的各频段地震记录合成为滤波去噪后的地震记录。理论模型和实际资料处理效果表明该方法能有效压制噪音,保护边界,保护同相轴的连续性,且灵活地保留地震记录中的有用信息。     

对地震图像进行保边滤波的非线性各向异性扩散算法

地震资料的噪音消除是地震资料处理的一个重要步骤,以往的地震资料滤波,都容易伤害地震资料的高频信号.原始地震图像属于线形纹理图像,地震同相轴表现为线条结构.基于偏微分方程的非线性各向异性扩散技术通过结构张量的特征向量控制扩散方向,利用扩散张量的特征值控制特征方向上的扩散量,对原始地震图像进行图像平滑处理,增强具有一致性的同向轴及其所反映的重要地质结构.     

Assessment of connectivity in a water‐stressed wetland (Kaabar Tal) of Kosi‐Gandak interfan,north Bihar Plains,India

Landscape elements respond to the processes acting on them, and this response connects with neighboring landscape units. The propagation, superposition, and interference of these responses are functions of the connectivity among the landscape units. Such landscape units are referred to as ‘Connectivity Response Units’ or CRUs that are in turn influenced by topography and landuse/landcover (LULC). The CRUs are obtained by the application of diffusion‐kernel based smoothing technique over the connectivity potential maps. A framework has been designed using the CRUs to understand the impacts of changing LULC on the connectivity structure in a relatively flat terrain under pre‐ and post‐monsoon scenarios. The proposed framework has been applied to a water‐stressed wetland occurring in an interfan setting in north Bihar plains, eastern India. It has also been demonstrated that CRUs can be used as a viable option for understanding the seasonal and temporal dynamics of connectivity structure in and around such wetlands and for guiding a rehabilitation strategy for such fragile ecosystems. Copyright © 2017 John Wiley & Sons, Ltd.     

Imaging artefacts of artificial diving waves in reverse time migration: cause analysis in the angle domain and an effective removal strategy

In areas with strong velocity gradients, traditional reverse time migration based on cross-correlation imaging condition not only produces low-frequency noise but also generates diving wave artefacts. The artefacts caused by diving waves have no typical low-frequency characteristics and cannot be eliminated by simple high-pass filtering approaches. We apply the wave-field decomposition imaging condition to analyse the causes of false images in reverse time migration by decomposing the full wave-field into up-going and down-going components in the angle domain. We find that artificial diving wave imaging artefacts, which are generated by the cross-correlation between the up-going source and down-going receiver wave-fields in areas with strong velocity gradients, arise at large angles. We propose an efficient strategy by means of the wavelength-dependent smoothing operator to eliminate artefacts from artificial diving waves in reverse time migration. Specifically, the proposed method provides more reasonable down-going wave-fields in areas with sharp velocity constructs by considering the factor of varying seismic wavelengths during wave propagation, and the artificial components of diving waves are eliminated in a straightforward manner. Meanwhile, the other wave-field components that contribute to true subsurface images are minimally affected. Benefiting from a smoothed velocity, the proposed method can be adapted to the traditional reverse time migration imaging frame, which reveals significant implementation potential for the seismic exploration industry. A salt model is designed and included to demonstrate the effectiveness of our approach.     

适用于热带气旋分析的动态合成方法

介绍跟随热带气旋的动态合成方法,可以避免把简单算术平均的合成方法用于热带气旋分析时,不可避免地会带来信息平滑的问题.该方法采用随热带气旋移动的动态坐标,热带气旋中心即为坐标的的原点,将各个样本相同坐标的格点进行算术平均即可得到动态合成场.该方法可以使热带气旋结构保持相对完整,而且热带气旋周围环流系统的相对位置也基本得到保留;并给出了一个例子说明该方法是适用于热带气旋分析的.     

Analysis on code multipath mitigation by phase—Aided smoothing

Multipath influence on code range under static condition is described firstly in this paper, and the problem that to what extent the phase-aided smoothing can mitigate multipath interference is detailed. Some problems regarding smoothing and mitigation are discussed. Suggestions based on the analysis has been made. Project supported by Opening Research Foundation from LIESMARS (No. WKL (97) 0103)     

带乘性噪声系统双滤器平滑及反褶积算法

在带乘性噪声系统（ＳＭＮ）间接平滑算法的基础上,通过构造一种新的ＳＭＮ逆向信息滤波算法,建立了ＳＭＮ的双滤器平滑和反褶积算法;为解决ＳＭＮ最优估计问题提供了新的方法。     

用差分GPS采集1∶5万公路数据的技术关键——兼述全国铁路数据采集的技术设想

讨论了利用差分 GPS技术进行 1∶ 5万国家空间基础地理信息公路层数据采集中遇到的几个问题和解决方法 ,对 1∶ 5万国家空间基础地理信息铁路层数据采集提出了利用 INTERNET网络中的 GPS精密星历和星钟差等资源进行事后单机定位事后广域差分的技术设想。