GA-BP网络模型在GPS似大地水准面精化中的应用     

彭祥国  王坚  许振问  王建鹏 《全球定位系统》2009,34(4):66-70

针对误差反向传播（BP）算法训练速度慢和易于陷入局部最小值的缺点，提出了利用遗传算法（GA）的全局寻优性，结合GA和BP的各自优点，分析和建立了进化神经网络（GA-BP）模型，并将该模型应用于似大地水准面模型精化。最后以南方某市E级GPS控制网高程数据为例，进行BP和GA-BP模型的对比实验，通过对内、外符合精度及MAPE（平均绝对误差百分比）指标分析，验证了该方法的可行性。  相似文献   

GPS卫星伪广播星历技术研究     

何丽娜  王解先 《海洋测绘》2008,28(4):11-14

通过GPS广播星历求出一个时间段内间隔一定时间的离散卫星三维坐标，以这些卫星坐标序列为已知数据反求星历参数的方法，论述和验证了当卫星坐标发生旋转变化时，解算得到的相应地面点坐标的旋转矩阵与卫星坐标发生旋转变化的矩阵具有相同的值。这对于实现GPS加密具有很大的意义。  相似文献   

三维激光扫描单点定位精度评定方法研究   总被引：3，自引：0，他引：3  

向娟  李钢  黄承亮  蒲玲媛 《海洋测绘》2009,29(3):68-70

三维激光扫描技术是当前的一种新技术，其仪器的精度评定方法还不完善，提出两种三维激光扫描单点定位精度评价方法，即外部符合精度评价方法和内部符合精度评价方法。介绍了两种方案的实施过程，并且通过实验进行了分析，得到了较好的评价结果。  相似文献   

A fuzzy dynamic flood routing model for natural channels     

R. Gopakumar  P. P. Mujumdar 《水文研究》2009,23(12):1753-1767

A fuzzy dynamic flood routing model (FDFRM) for natural channels is presented, wherein the flood wave can be approximated to a monoclinal wave. This study is based on modification of an earlier published work by the same authors, where the nature of the wave was of gravity type. Momentum equation of the dynamic wave model is replaced by a fuzzy rule based model, while retaining the continuity equation in its complete form. Hence, the FDFRM gets rid of the assumptions associated with the momentum equation. Also, it overcomes the necessity of calculating friction slope (S_f) in flood routing and hence the associated uncertainties are eliminated. The fuzzy rule based model is developed on an equation for wave velocity, which is obtained in terms of discontinuities in the gradient of flow parameters. The channel reach is divided into a number of approximately uniform sub‐reaches. Training set required for development of the fuzzy rule based model for each sub‐reach is obtained from discharge‐area relationship at its mean section. For highly heterogeneous sub‐reaches, optimized fuzzy rule based models are obtained by means of a neuro‐fuzzy algorithm. For demonstration, the FDFRM is applied to flood routing problems in a fictitious channel with single uniform reach, in a fictitious channel with two uniform sub‐reaches and also in a natural channel with a number of approximately uniform sub‐reaches. It is observed that in cases of the fictitious channels, the FDFRM outputs match well with those of an implicit numerical model (INM), which solves the dynamic wave equations using an implicit numerical scheme. For the natural channel, the FDFRM outputs are comparable to those of the HEC‐RAS model. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

双向定时近周日误差成分初步分析     

刘利  韩春好  唐波 《天文学进展》2007,25(3):279-283

该文介绍了利用地球同步卫星定位系统进行双向定时的基本原理,采用北京和乌鲁木齐两站的试验数据进行了计算分析,发现双向定时结果明显存在周期性变化,并且两地结果随地方时的变化趋势基本一致。谱分析表明:两站的主要周期谱基本一致,都比较明显地存在近周日和近半日变化。这种周期性变化可能主要由电离层延迟随地方时的变化引起。  相似文献   

Accelerating the convergence of coupled geomechanical‐reservoir simulations     

L. Jeannin  M. Mainguy  R. Masson  S. Vidal‐Gilbert 《国际地质力学数值与分析法杂志》2007,31(10):1163-1181

The pressure variations during the production of petroleum reservoir induce stress changes in and around the reservoir. Such changes of the stress state can induce marked deformation of geological structures for stress sensitive reservoirs as chalk or unconsolidated sand reservoirs. The compaction of those reservoirs during depletion affects the pressure field and so the reservoir productivity. Therefore, the evaluation of the geomechanical effects requires to solve in a coupling way the geomechanical problem and the reservoir multiphase fluid flow problem. In this paper, we formulate the coupled geomechanical‐reservoir problem as a non‐linear fixed point problem and improve the resolution of the coupling problem by comparing in terms of robustness and convergence different algorithms. We study two accelerated algorithms which are much more robust and faster than the conventional staggered algorithm and we conclude that they should be used for the iterative resolution of coupled reservoir‐geomechanical problem. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

面向流媒体传输的空间数据变化累积模型     

陈刚  赵斌  胡友健  潘雄 《测绘学报》2009,38(6):0-481

将流媒体技术引入到以矢量数据为主的网络GIS传输中,其关键是建立逐级精细化的多层次表达模型,并在服务器端数据预组织上建立线性索引结构。本研究针对该目标建立一种矢量数据多重表达的新模型,即变化累积模型,认为尺度空间中从粗到细的数据表达过程是一些"变化"的累积,"变化"表现为两个连续尺度表达间的差别,通过"变化"元素的逐渐增加或减少来实现渐进传输。基于该模型对面状数据渐进式传输进行研究,将多边形分级剖分为一系列凸壳或外接矩形的基础上建立变化累积模型,通过剖分元素的组合完成渐进式流媒体传输。  相似文献   

VRS RTK技术在QuickBird遥感影像定位研究中的应用     

王伟  童小华  刘世杰 《地理信息世界》2007,5(6):60-65

基于虚拟参考站(Virtual Reference Station,VRS)的RTK定位技术是一种以载波相位观测值为基础的实时差分定位技术,与传统测量手段相比,具有快速、高效的特点,且具有较高的测量精度。本文主要探讨基于VRS RTK技术在QuickBird遥感影像定位研究中的应用,包括VRS RTK定位技术原理、基于VRS RTK的遥感影像控制点处理方法,以及基于此的遥感影像定位模型和定位精度。  相似文献   

GPS���ٶ�λ�в�̬��������򻯿���ⷨ   总被引：1，自引：1，他引：0  

常志巧  郝金明  张成军  崔建勇 《大地测量与地球动力学》2008,28(3):83-86

???GPS?????λ??????????????????????????????????????????????M??????????????μ??????????????????????????????????????????????е????????????????????????÷??????п???????????????????????????  相似文献   

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汪平  郝金明  沈国康  王兰 《大地测量与地球动力学》2009,29(5):112-115

???GPSα????λ????????????????????μ?????????????λ??????????????ù????????????????????????????????棨???棩?????????????????????????????????α?????????????????????α???????????????????????λ??????????·??????????????????λ???????????????????????????????ν????????????????????????Ч????????λ?????????????????  相似文献