Modeling spatial autocorrelation in spatial interaction data: empirical evidence from 2002 Germany journey-to-work flows   总被引：3，自引：3，他引：0  

Daniel A. Griffith 《Journal of Geographical Systems》2009,11(2):117-140

Since before the inception of work by Okabe, the intermingling of spatial autocorrelation (i.e., local distance and configuration) and distance decay (i.e., global distance) effects has been suspected in spatial interaction data. This convolution was first treated conceptually because technology and methodology did not exist at the time to easily or fully address spatial autocorrelation effects within spatial interaction model specifications. Today, however, sufficient computer power coupled with eigenfunction-based spatial filtering offers a means for accommodating spatial autocorrelation effects within a spatial interaction model for modest-sized problems. In keeping with Okabe’s more recent efforts to dissemination spatial analysis tools, this paper summarizes how to implement the methodology utilized to analyze a particular empirical flows dataset.

Daniel A. GriffithEmail:

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基于小波滤波的神经网络变形预测     

李维付  徐亚明  郭波  李建虎 《地理空间信息》2009,7(3):132-135

运用小波滤波的的优越性,消除数据噪声,使数据更加的接近真实的数据和更具规律性,有利于我们对数据发展趋势的预测。对消噪后的数据,利用BP神经网络强大的学习能力建立预测网络。在建立网络时,输入样本为监测k时段序列k和第k-1时段变形量与再k-2时段变形量之差组成的二维向量,目标样本为小波滤波后的变形量。并与GM（1,1）。模型和回归模型进行了对比。  相似文献   

基于最小均方误差算法消除GPS接收机噪声          下载免费PDF全文

王强 《海洋测绘》2009,29(5):61-63

从解决GPS接收机受干扰的实际需求出发,阐述了基于LMS算法的自适应滤波器基本原理和不同的噪声产生方式,并对GPS接收机仿真信号与噪声进行叠加。最后用基于LMS算法的自适应滤波器对仿真信号进行消噪处理,得到良好的消噪效果,证明了基于LMS算法的自适应滤波器能够应用于GPS接收机滤波系统。  相似文献   

Short-term (≤2 yrs) estuarine mudflat and saltmarsh sedimentation: High-resolution data from ultrasonic altimetery, rod surface-elevation table, and filter traps     

Claire Marion  Edward J. Anthony  Alain Trentesaux   《Estuarine, Coastal and Shelf Science》2009,83(4):475-484

Rates of short-term (up to 2 years) bed elevation change and sedimentation from mudflats to salt marshes were measured in a rapidly infilling macrotidal estuary using an original combination of three high-resolution techniques: an ultrasonic altimeter, the Rod Surface-Elevation Table (RSET) method, and filter traps. The Authie estuary is located on a straight, sand-rich coast and is undergoing rapid infill under the influence of flood-dominant tides reinforced by wave action. The estuarine sediment suite consists of both mud and sand derived from the sea, of sand derived from storm wave erosion of dunes lining the north bank of the estuary, and, to a much smaller extent, of mud from the river catchment. Bed elevation change and sedimentation rates show an expected increase with the duration of tidal flooding (hydroperiod) in both space and time. The estuarine bed sediment suite changes from sandy at the mouth to muddy within the low-energy inner estuary, where mudflats are rapidly accreting, paving the way for the formation of increasingly denser and mature salt marshes from the high-sedimentation pioneer zone to the upper marsh where annual sedimentation is very low. Recorded variability in rates of bed elevation change and sedimentation reflect the influence of estuarine macro-scale and local sediment transport and depositional processes in a macrotidal context dominated by high inputs of allochthonous sediments.  相似文献   

一种低信噪比下PN码的快速捕获技术     

曾海彬  王天宝 《成都信息工程学院学报》2009,24(2):126-128

直扩系统中,为了硬件实现的简便,PN码的捕获一般都采用串行搜索的方法.但当PN码很长时,由于搜索相位点很多,串行搜索法将使捕获时间过长.并且当信噪比较低时,会有较高的虚警概率.这些都会使系统的捕获性能降低.提出一种基于匹配滤波器的快速捕获算法,改善了在极低信噪比下的性能.降低了平均捕获时间.  相似文献   

���μ����Kalman�˲�״̬ģ�͵ıȽϷ���   总被引：2，自引：0，他引：2  

戴吾蛟  伍锡锈 《大地测量与地球动力学》2009,29(6):88-92

??????λ??????μ???У?Kalman?????????????????????????????????????????????????Щ??????????????????????????????????????????????????????Щ????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????У????????????Kalman?????????????????????????????????μ??????е??????  相似文献   

白噪声Kalman滤波模型在GPS单向授时中的应用     

陈军  李建文  张成军  刘晓刚 《海洋测绘》2010,30(1):29-31

全球定位系统(GPS)的应用越来越广泛,尤其是高精度的星载原子钟使得授时的精度得到了很大的提高。针对GPS授时过程中接收机受到各种噪声的影响,利用Kalman滤波原理,建立状态方程和观测方程,对噪声进行分类并加以讨论。运用Kalman滤波原理对接收机钟差数据进行分析,计算结果表明Kalman滤波可提高GPS单向授时精度。  相似文献   

δC and δN biogeographic trends in rocky intertidal communities along the coast of South Africa: Evidence of strong environmental signatures     

Jaclyn M. Hill  Christopher D. McQuaid 《Estuarine, Coastal and Shelf Science》2008

Ecosystem dynamics driven by top-down controls have been well documented in rocky intertidal communities, while the effects of bottom-up influences are comparatively poorly understood. We hypothesized that large-scale signatures of the physical environment may be identifiable along the South African coastline as it is subject to two very different current systems (Benguela and Agulhas Currents) that profoundly influence primary production and thus both food type and availability. Through stable isotope analysis, we examined biogeographic patterns in multiple trophic levels at four sites along a 1400-km stretch of South African coastline and investigated the dietary role of macroalgal-derived organic carbon in rocky intertidal communities. The general positioning of trophic groups was comparable across all sites, with animals from the same trophic levels grouping together and with a δ¹⁵N fractionation of 1–2‰ between levels. The species found at all sites demonstrated east–west δ¹⁵N enrichment, presumably reflecting a biogeographic shift in nitrogen sources linked to upwelling on the west coast. Filter-feeders gave particularly clear results. Using discriminant analysis, mussels could be categorized into four geographic groups based on carbon and nitrogen signatures: east coast, southeast coast, south-west coast and west coast. Barnacles and polychaetes showed similar geographic groupings to mussels, but with shifts in actual values (1‰ depletion in δ¹³C and 3‰ enrichment in δ¹⁵N relative to mussels). This suggests that fractionation varies between species within a trophic level.  相似文献   

Adsorption of extracellular proteases in seawater onto filters during size fractionation     

Yumiko Obayashi  Satoru Suzuki 《Journal of Oceanography》2008,64(3):367-372

In aquatic environments extracellular enzymes are bound to microbial cells or exist in a free and adsorbed state. Various filters have been used to fractionate these enzymatic activities, but enzymes may be readily adsorbed onto some materials, and such adsorption can induce errors in the estimation of enzymatic activity. In this study we examined three filters to determine the most suitable filter for fractionation when estimating proteolytic enzyme activity in seawater. We found that the polycarbonate Nuclepore membrane, widely used for size fractionation because of its pore-size accuracy, was the most favorable for this purpose, even though it adsorbed slightly more enzymes than the low-protein-binding polyethersulfone membrane. We also found that trypsin-and chymotrypsin-type enzymes were more easily adsorbed than aminopeptidases.  相似文献   

基于卡尔曼滤波的INS／USBL水下导航系统模型研究   总被引：1，自引：0，他引：1  

李守军  陶春辉  包更生 《海洋技术学报》2008,27(3)

简述惯性导航技术(INS)和超短基线定位技术(USBL),并分析了各自的优缺点.为了满足深海作业对导航定位高精度、高数据更新率的技术需求,提出基于卡尔曼滤波技术(Kalman Filter)实现INS和USBL的融合集成,研究了系统模型,进行了水下定位试验,给出了误差分析结果,证明了模型的可靠性.  相似文献