武汉市龙王庙险段水下地形监测及分析

该文根据武汉市龙王庙堤防险段水下地形监测特点,介绍了一种传统测量技术与现代测量技术结合的监测模式,论述了该险段水下地形监测方案,并对监测数据进行了分析,得出了三点结论。     

一种新的GPS变形监测算法及其在东海大桥上的应用

在建筑物变形监测中,嵌入GPS实时动态(Real-time Kinematic,RTK)方法的普通双频RTK接收机不能应对基线较长且电离层比较活跃的情况。因此,提出一种基于无电离层三差观测量的扩展Ka1man滤波模型,并通过试验与普通RTK接收机进行比较,证明了其可行性。     

运用移动网络设计的监控定位移动目标系统

随着生活的发展,国人对自身安全越来越重视,移动监控定位系统技术趋于成熟。对需监控目标进行实时电子监控已成为可能。本文从GSM;GPS;SMS等几项技术来阐述移动监控定位系统的设计。     

一种新型的电子海图显示系统开发方案

在分析国外一些成熟的ECDIS系统和先进的GIS系统基础上，提出了一种新的开发电子海图显示系统的方案，并按照这一方案开发了可以作为舰船导航信息综合显示平台的电子海图显示系统。     

An empirical study to determine freight travel time at a major port

Abstract

This paper examines the reliability measures of freight travel time on urban arterials that provide access to an international seaport. The findings indicate that the reliability index calculated by the median of travel time, which is less sensitive to extreme values in a highly skewed distribution, is more appropriate. This paper also examines several statistical distributions of travel time to determine the best fit to the data of freight trips. The results of goodness-of-fit tests indicate that the log-logistic is the best statistical function for freight travel time during the midday off-peak period. However, the lognormal distribution represents a better fit to arterials with heavily congested traffic during peak periods. Additionally, travel time prediction models identify the relationships between travel time, speeds and other factors that affect travel time reliability. The analysis suggests that incident-induced delays and speed fluctuations primarily contributed to the unreliability of freight movement on the urban arterials.     

GPS接收机C/A码跟踪算法及环路控制策略

高动态GPS接收机指在接收信号有较大的多普勒频率偏移及其一阶、二阶导数存在时仍能正常工作的GPS接收机。针对高动态环境下伪码跟踪所遇到的问题,重点研究了与高动态载波跟踪算法相匹配的、基于载波辅助技术的归一化非相干点积功率伪码跟踪算法,以及预检积分时间可变的伪码跟踪环路控制策略。采用MATLAB建立了系统模型,仿真结果表明:采用伪码跟踪算法以及结合相应的高动态载波跟踪算法的伪码跟踪控制策略的GPS接收机能在加速度为80 g,加速度为10 g.s-1的指标下正常工作。     

Developing travel time estimation methods using sparse GPS data

Existing methods of estimating travel time from GPS data are not able to simultaneously take account of the issues related to uncertainties associated with GPS and spatial road network data. Moreover, they typically depend upon high-frequency data sources from specialist data providers, which can be expensive and are not always readily available. The study reported here therefore sought to better estimate travel time using “readily available” vehicle trajectory data from moving sensors such as buses, taxis, and logistical vehicles equipped with GPS in “near” real time. To do this, accurate locations of vehicles on a link were first map-matched to reduce the positioning errors associated with GPS and digital road maps. Two mathematical methods were then developed to estimate link travel times from map-matched GPS fixes, vehicle speeds, and network connectivity information with a special focus on sampling frequencies, vehicle penetration rates, and time window lengths. Global positioning system (GPS) data from Interstate I-880 (California) for a total of 73 vehicles over 6 h were obtained from the University of California Berkeley's Mobile Century Project, and these were used to evaluate several travel time estimation methods, the results of which were then validated against reference travel time data collected from high resolution video cameras. The results indicate that vehicle penetration rates, data sampling frequencies, vehicle coverage on the links, and time window lengths all influence the accuracy of link travel time estimation. The performance was found to be best in the 5-min time window length and for a GPS sampling frequency of 60 s.     

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云计算借助高速网络将各种计算能力联接起来,为交通信息提供了几乎无上限的可伸缩的计算能力. 本文分析了交通信息云计算的优势、特征、方法和部署,认为交通信息云计算也是一种信息高效采集和服务的概念,是实现交通行为控制的基础. 以车辆GPS定位信息的获取、传送、计算和应用为例,对比了浮动车信息现有处理模式与云计算信息处理模式,提出了以云计算模式产生高效用度、闭环可验证的个性化路径导航信息作用于海量驾驶员个体,实现控制性路径诱导的方法.     

GPS导航产品的验证内容和测试方法

介绍GPS导航产品,概述导航产品的验证内容,结合实际重点探讨合理性/实用性验证和实车验证,提出一些方法和经验。     

基于GSM网络的车载远程报警系统的设计

采用GSM技术设计了车载远程报警系统。该系统以微处理器为控制核心,利用传感器的报警信号,使GSM模块在发生警情的同时发送短信到指定的号码,并且通过CAN总线控制车身其它单元,有效地提高了汽车防盗性能。