基于ARM的GPS接收机设计

随着GPS系统的广泛应用,作为系统用户设备部分的GPS接收机,已经成为国内外的研发热点。本介绍了一种基于ARM核的双芯片（即基带处理器＋射频前端）GPS接收机的硬件设计方案,该GPS接收机具有体积小、功耗低、集成度高的特点。     

短消息在交通信息发布系统中的应用与研究

为满足出行者对实时交通信息的需求，在已获得交通信息的基础上，结合出行者需求的个性化、多样化等特点，研究了实时交通信息的短消息动态发布模式。以通用SMIP协议为承载，采用自定义的应用层协议；设计伺服和推送两种发布服务方式，达到更好的手机终端与交通信息平台之间的信息协同效果。最后，以Java开源软件为平台开发交通信息的短消息动态发布子系统，使已有交通信息发布系统的基本功能得到进一步的拓展。     

GPS掩星资料的一维变分同化与观测算子

在应用掩星观测资料反演温度和水汽的过程中,存在一个模糊度问题。合理利用背景场和观测量的误差特性,变分同化反演技术可以克服这个困难,并改进反演剖面的质量。采用一维变分同化反演技术,可以从弯曲角或折射率剖面直接反演大气层的压强、温度、和水汽的剖面,并使结果更加合理。变分同化反演是地基和天基GPS技术服务大气科学的主要途径,如何选择合适的观测算子直接进入气象预报的3-维或4-维同化模式成为GPS气象学最重要的环节之一。本文介绍一维变分同化反演技术、各类观测算子,这些基本方法也可以应用到3-维或4-维同化模式中。     

直接解算三维变形量GPS软件(Gquicks1.5)研制及在三峡库区滑坡监测中的应用

本文论述了不解算GPS基线,而直接解求三维变形量的原理及正确性的验证,介绍了研制的Gquicks1.5版本软件系统流程及主要功能模块。通过在三峡库区GPS滑坡监测实践的应用,总结了GPS观测纲要,提出了一些有益的结论与建议。     

GPS和GLONASS组合系统

现在天空中有两种规模最大的卫星导航系统，如果把它们组合起来就具有明显的优势，因为GPS和GLONASS的组合系统在任何时间内都能接收到11颗卫星的组合，它能很好地改善系统的几何因子，使得系统可用性达到100%，接收机自主完好性监测（RAIM）也能大大地提高。单独使用GPS或GLONASS为提高定位精度须采用差分技术，使用差分技术就增加了地面基准站的投入和系统的复杂性，在组合系统下本身精度就提高多了。由于GPS和GLONASS具有不同的轨道面，卫星分布也不同，GPS适合于中纬度地区，GLONASS适合于高纬度地区，两者兼容互补作用 很强，所以GPS和GLONASS组合系统的实用意义特别重大。我国科技工作者应深入研究这种组合系统以减小GPS的使用风险。     

基于WINCE的多功能车载播报器设计

针对目前公交车载设备的现状,提出了一款基于wince操作系统和GPS全球定位技术的嵌入式多功能车载播报器,并介绍其功能、组成原理和关键技术.该系统采用S3C2416为主控单元的嵌入式硬件平台,OS采用wince5.0为内校,SD卡作为存储媒介,预留3G接口,并为公交车上现存的LED显示屏、视频监控等硬件设备预留接口,实...     

中国低纬度地区GPS周跳季节依赖特点分析

利用中国低纬度地区6个GPS观测站2001年的观测数据,分析了该地区日周跳发生次数与季节的关系．结果表明：该地区的日周跳发生次数与季节关系明显,GPS周跳主要发生在两分季附近（3～5月和9～11月）,且一些日期6个台站的日周跳发生次数变化趋势一致,这种周跳的季节依赖特点与同期我国广州电离层扩展F出现的季节依赖特点类似．结合周跳的地方时依赖特点,可以推断仰角大于一定角度时的周跳与该地区上空电离层不均匀结构有一定的关系．通过不同地磁纬度观测站日周跳次数的比较,可以看到在同一时间段内该地区处于较高纬度的LUZH台站的日周跳次数要明显小于其他台站．以相距很近的两个GPS台站2001年日周跳次数存在明显差异这一事实为出发点,分析了同样电离层条件下周跳对GPS接收机本身硬件质量的依赖性．     

现代卫星导航系统技术特点与发展趋势分析

简要介绍了美国GPS系统、饿罗斯GLONASS系统、欧洲Galileo系统、中国北斗卫星导航系统、以及日本和印度的区域卫星导航系统的发展状况．重点研究了GPS系统星座维持、有效载荷、自主导航、信号调制和地面站改造等最新技术特征,以及GPSⅢ系统技术及研究进展,分析论证了卫星导航系统技术的发展趋势,为我国卫星导航系统建设规划提供参考．     

汽车与行人交通冲突中驾驶员操作特性研究

在北京50辆出租车上安装了图像式行驶记录仪，进行了为期一年真实道路环境下的交通冲突调查。本文基于收集的交通冲突数据，从冲突时间、地点、自车速度和驾驶员的制动操作等方面对车辆与行人的冲突特征进行分析，提出了车与行人冲突发生的原因，为汽车与行人事故的预防提供了理论基础。     

基于图像式行驶记录仪的汽车-自行车交通冲突特性研究

汽车与自行车事故在我国交通事故总数中占有重要比例。为了研究汽车与自行车交通冲突／事故特性,本文选用50辆出租车,利用图像式汽车行驶记录仪在北京市开展了为期一年的交通冲突调查,从冲突类型、冲突时间、冲突地点及交通控制方式、冲突车速及交通流、驾驶员视线遮挡等方面综合分析汽车一自行车冲突特性,研究结果对道路交通安全管理、道路设计及事故预防技术具有重要的意义。     

The Role of Survey Data in Nowcasting Euro Area GDP Growth

This paper evaluates the impact of new releases of financial, real activity and survey data on nowcasting euro area gross domestic product (GDP). We show that all three data categories positively impact on the accuracy of GDP nowcasts, whereby the effect is largest in the case of real activity data. When treating variables as if they were all published at the same time and without any time lag, financial series lose all their significance, while survey data remain an important ingredient for the nowcasting exercise. The subsequent analysis shows that the sectoral coverage of survey data, which is broader than that of timely available real activity data, as well as their information content stemming from questions focusing on agents' expectations, are the main sources of the ‘genuine’ predictive power of survey data. When the forecast period is restricted to the 2008–09 financial crisis, the main change is an enhanced forecasting role for financial data. Copyright © 2015 John Wiley & Sons, Ltd.     

Overreaction in Survey Exchange Rate Forecasts

We use survey data on five bilateral exchange rates to provide empirical evidence of the fact that professional forecasters of foreign exchange rates behave irrationally, in the specific sense that they respond inaccurately to available information in the market when forming their predictions. In particular, we find systematic biases in the forecasts resulting in the overreaction of analysts to past information contained in the exchange rate dynamics: forecasters change their prediction more than it would be rational on the basis of past realized changes. In addition, forecasters are heterogeneous in their irrationality: low performers in previous periods show a more pronounced overreaction effect. This can be read as an indication of perpetration of past errors and continued inability to learn from the past. In the second part of the paper, we exploit the novel structure of our dataset, which consists of survey data extracted from the Bloomberg platform and readily available to anyone. This feature allows us to consider their own and others' past forecasts as part of the information set that analysts use in making their predictions. By using past forecasts as proxies for relevant macroeconomic variables, we find evidence that analysts fail to correctly process not only the information contained in the spot rate past dynamics but also the information in this broader set. We see this as confirmation of the existence of inefficiency and heterogeneity between low and high performers also when full information is available. Copyright © 2014 John Wiley & Sons, Ltd.     

Measuring Disagreement in Qualitative Expectations

We assess how well measures of disagreement in qualitative survey expectations reflect disagreement in corresponding quantitative expectations. We consider a variety of measures, belonging to two categories: measures of dispersion in nominal and ordinal variables and measures based on the probability approach of Carlson and Parkin (Economica, 1975; 42 , 123–138). Using data from two household surveys that collect both qualitative and quantitative inflation expectations, we find that the probability approaches with time‐varying categorization thresholds and either a piecewise uniform or t distribution perform best and the resulting disagreement estimates are highly correlated with the benchmark. Copyright © 2015 John Wiley & Sons, Ltd.     

Nowcasting and predicting data revisions using panel survey data

The qualitative responses that firms give to business survey questions regarding changes in their own output provide a real‐time signal of official output changes. The most commonly used method to produce an aggregate quantitative indicator from business survey responses—the net balance or diffusion index—has changed little in 40 years. This paper investigates whether an improved real‐time signal of official output data changes can be derived from a recently advanced method on the aggregation of survey data from panel responses. We find, in a New Zealand application, that exploiting the panel dimension to qualitative survey data gives a better in‐sample signal about official data than traditional methods. Out‐of‐sample, it is less clear that it matters how survey data are quantified, with simpler and more parsimonious methods hard to improve. It is clear, nevertheless, that survey data, exploited in some form, help to explain revisions to official data. Copyright © 2009 John Wiley & Sons, Ltd.     

GPS连续运行参考站网络分析及网络参数估计

本文分析了各种构网方式对网络模糊度解算效率的影响;阐述了最优双差观测值和观测方程的双差映射生成方法;本文在考虑网络参数的各种相关性的基础上,建立了整网卡尔曼滤波方程来整体估计网络参数,并使用LAMBDA方法解算具有奇异方差阵的模糊度。使用成都GPS综合服务网的子网数据验证了该模糊度算法,使用该网的实时数据计算了天顶对流层延迟网络参数,并与Gamit估值进行了对比。     

A note on the predictive power of survey data in nowcasting euro area GDP

This paper investigates the trade‐off between timeliness and quality in nowcasting practices. This trade‐off arises when the frequency of the variable to be nowcast, such as gross domestic product (GDP), is quarterly, while that of the underlying panel data is monthly; and the latter contains both survey and macroeconomic data. These two categories of data have different properties regarding timeliness and quality: the survey data are timely available (but might possess less predictive power), while the macroeconomic data possess more predictive power (but are not timely available because of their publication lags). In our empirical analysis, we use a modified dynamic factor model which takes three refinements for the standard dynamic factor model of Stock and Watson (Journal of Business and Economic Statistics, 2002, 20, 147–162) into account, namely mixed frequency, preselections and cointegration among the economic variables. Our main finding from a historical nowcasting simulation based on euro area GDP is that the predictive power of the survey data depends on the economic circumstances; namely, that survey data are more useful in tranquil times, and less so in times of turmoil.     

Forecasting with panel data

This paper gives a brief survey of forecasting with panel data. It begins with a simple error component regression model and surveys the best linear unbiased prediction under various assumptions of the disturbance term. This includes various ARMA models as well as spatial autoregressive models. The paper also surveys how these forecasts have been used in panel data applications, running horse races between heterogeneous and homogeneous panel data models using out‐of‐sample forecasts. Copyright © 2008 John Wiley & Sons, Ltd.     

What can we learn from the fifties?

Economists have increasingly elicited probabilistic expectations from survey respondents. Subjective probabilistic expectations show great promise to improve the estimation of structural models of decision making under uncertainty. However, a robust finding in these surveys is an inappropriate heap of responses at “50%,” suggesting that some of these responses are uninformative. The way these 50s are treated in the subsequent analysis is of major importance. Taking the 50s at face value will bias any aggregate statistics. Conversely, deleting them is not appropriate if some of these answers do convey some information. Furthermore, the attention of researchers is so focused on this heap of 50s that they do not consider the possibility that other answers may be uninformative as well. This paper proposes to take a fresh look at these questions using a new method based on weak assumptions to identify the informativeness of an answer. Applying the method to probabilistic expectations of equity returns in three waves of the Survey of Economic Expectations in 1999–2001, I find that: (i) at least 65% of the 50s convey no information at all; (ii) it is the answer most often provided among the answers identified as uninformative; (iii) but even if the 50s are a major contributor to noise, they represent at best 70% of the identified uninformative answers. These findings have various implications for survey design.