�����쳣ƥ�丨����������ģ�͵��Ż�   总被引：2，自引：1，他引：1  

戴全发  许大欣  蔡小波  王勇 《大地测量与地球动力学》2007,27(4):31-34

???????????????1??????????????????????????????????????????????????λ?ù???????????????????????λ??????????????е????????????????е????????????????????????????????????????????????????????????????????????????????????仯?????????и???????Ч????  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   

Discrete time-delay control of an autonomous underwater vehicle: Theory and experimental results     

R.P. Kumar  D. Sen 《Ocean Engineering》2009,36(1):74-81

A discrete time-delay control (DTDC) law for a general six degrees of freedom unsymmetric autonomous underwater vehicle (AUV) is presented. Hydrodynamic parameters like added mass coefficients and drag coefficients, which are generally uncertain, are not required by the controller. This control law cancels the uncertainties in the AUV dynamics by direct estimation of the uncertainties using time-delay estimation technique. The discrete-time version of the time-delay control does not require the derivative of the system state to be measured or estimated, which is required by the continuous-time version of the controller. This particularly provides an advantage over continuous-time controller in terms of computational effort or availability of sensors for measuring state derivatives, i.e., linear and angular accelerations. Implementation issues for practical realization of the controller are discussed. Experiments on a test-bed AUV were conducted in depth, pitch, and yaw degrees of freedom. Results show that the proposed control law performs well in the presence of uncertainties.  相似文献   

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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   

����ԳƷ��ڵ��㶨λ�е�Ӧ��   总被引：1，自引：0，他引：1  

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   

The onset of fish colonization in a coastal defence structure (Chioggia,Northern Adriatic Sea)     

M. Pizzolon  E. Cenci  C. Mazzoldi 《Estuarine, Coastal and Shelf Science》2008

Coastal defence structures constitute the most extensive hard substrates of the Northwestern Adriatic Sea and are known to sustain rich benthic and nektonic communities. To appreciate the pattern of colonization, we studied the fish assemblage of a recently deployed breakwater. We compared observations from two years, the different sides (landward and seaward) of the barrier, and the two fringes, characterized by timing of work completion. The results indicate that colonization, still in process, follows different patterns among species. Benthic and necto-benthic species presented a striking increase in abundance and richness in the second year of colonization, while more mobile species did not evince any variation between years. Differences in mobility among species suggest that the latter group may have reached the breakwater from nearby artificial substrates, whereas the former colonized the new structure as recruits. In addition, fish assemblages differed between the two sides, likely due to variation in the environmental characteristics, and according to depth, reflecting species preferences.  相似文献   

区域性网络定位服务应用技术探讨     

陈日高  徐益群  陈江  白清波  唐磊 《海洋测绘》2008,28(1):80-82

通过建立区域连续运行卫星基准站网络系统，建立一种新型定位测量与服务模式，取代现有传统标志式控制点位保存、管理与应用模式，实现虚拟化的、现代网络定位服务，并介绍了不同的测绘精度需求的作业与应用模式。  相似文献   

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廖成旺  邓涛  丁炜  王浩  谭耀银  陈卫民 《大地测量与地球动力学》2007,27(6):61-64

???????????????????????????????????????????????????????????????????????ж?λ?????????????????????????????????Σ??????λ?????????????????????????????????????????????μ???????????????б???????????????????????????????ú???????????????????????????????????????Ч?????б??????????????????ò??ù??????о????λ???λ?????  相似文献   

Adaptive fuzzy controller design for dynamic positioning system of vessels     

《Applied Ocean Research》2015

This paper develops an adaptive fuzzy controller for the dynamic positioning (DP) system of vessels with unknown dynamic model parameters and unknown time-varying environmental disturbances. The controller is designed by combining the adaptive fuzzy system with the vectorial backstepping method. An adaptive fuzzy system is employed to approximate the uncertain term induced by unknown dynamic model parameters and unknown time-varying environmental disturbances. It is theoretically proved that the proposed adaptive fuzzy DP controller can make the vessel be maintained at the desired values of its position and heading with arbitrary accuracy, while guaranteeing the uniform ultimate boundedness of all signals in the closed-loop DP control system of vessels. Simulation studies with comparisons on a supply vessel are carried out, and the results illustrate the effectiveness of the proposed control scheme.  相似文献