大型CORS网基线向量的分布式处理

信息技术的发展极大地推动了CORS站网数据处理理论与应用的研究进展。本文针对单机处理大型CORS网基线时站点规模受限和时效性差的问题,研究了基线解算的分布式处理流程和方法。应用分布式文件系统(HDFS)建立了CORS网数据的分布式存储和传输功能,基于Bernese处理引擎(BPE)实现了Bernese 5.0功能模块的并行化调用,基于Ambizap算法建立了分布式PPP解算和分布式独立基线解算的基线向量整网解算方法。算例表明,8个节点处理109个测站1 d的30 s采样间隔观测数据,比单机集中处理的加速比提高了6倍。     

应用Bernese5．0软件进行精密单点定位计算

介绍了Bernese5．0软件的整体解算流程,并应用其精密单点定位（PPP）处理引擎对沈阳市连续运行参考站基准站的位置进行了计算并与双差结果进行了比对,证明了采用Bernese5．0软件进行精密单点定位,其精度完全可以满足要求。     

非差模式的GNSS数据并行解算设计及实现

基于精密单点定位技术的非差模式是当前GNSS数据处理的主要策略之一。随着测站规模的增大,非差模式的处理时间也线性递增,传统的串行处理方法需消耗大量的计算时间。采用工厂模式和责任链模式实现了非差精密单点定位;利用轻量级的并行编程技术从底层设计并实现了基于任务的非差多核并行解算;进一步在网络多节点环境中建立并发布非差计算服务,实现了网络多节点协同并行解算GNSS数据。通过大量数据的测试与试验,验证了多核多节点的非差并行解算方案的高效性。试验结果表明,单节点多核并行、双节点网络并行、四节点网络并行、六节点网络并行的计算效率分别比单节点串行方案平均提高了2.74,5.30,9.38和14.69倍。     

非组合精密单点定位算法精密授时的可行性研究

利用基于GPS双频原始观测数据的非组合精密单点定位(PPP)算法进行精密授时,给出了其数学模型与数据预处理策略。实验结果表明,非组合PPP算法可以有效避免传统PPP算法由于观测值组合过程中观测噪声及多路径效应误差被放大而造成的对接收机钟差解算的不利影响,实现亚纳秒级(0.3 ns)的钟差解算精度;同等条件下,非组合PPP算法授时精度优于传统PPP算法,可以用于精密授时解算。     

北斗/GPS实时精密卫星钟差融合解算模型及精度分析

实时GNSS精密单点定位(PPP)技术必须使用实时的高精度卫星精密轨道和钟差。本文研究了精密卫星钟差融合解算模型及策略,并利用滤波算法实现了北斗/GPS实时精密卫星钟差融合估计算法。仿真实时试验结果显示:获得的北斗/GPS实时钟差与GFZ事后多GNSS精密钟差(GBM)的标准差在0.15 ns左右;使用该钟差进行GPS动态PPP试验,收敛后水平精度优于5 cm,高程精度优于10 cm;使用仿真实时钟差进行的北斗动态PPP与使用GFZ事后多GNSS精密钟差开展的试验相比精度相当,可实现分米级定位。     

GNSS精密单点定位技术及应用进展

综合分析讨论了GNSS精密单点定位(PPP)技术及应用的最新进展。重点对GNSS精密单点定位实数解、固定解、实时精密单点定位、PPP-RTK和多频多系统精密单点定位等5个方面的核心关键技术和实现方法进行了总结和讨论。结合PPP技术的特点和优势,论述了PPP在低轨卫星定轨、地震、对流层和电离层等方面的典型应用。针对多频多系统GNSS的最新发展动态,展望了PPP技术今后的发展趋势,并指出了精密单点定位技术和推广应用还有待进一步研究的问题。     

基于GNSS精密单点定位的高精度云平台授时

采用GNSS精密单点定位(PPP)技术和时钟驯服技术,构建了基于PPP的云平台高精度授时方案,研制了搭载多系统GNSS接收机板卡、恒温晶振(OCXO)和数字信号处理器(DSP)的授时原理样机。利用协同精密定位平台分析中心(武汉)提供的5 s间隔卫星轨道和钟差产品,采用PPP技术实时解算授时终端坐标和钟差,通过驯服恒温晶振输出亚纳秒精度的1 PPS,实现了长时间高精度的授时能力。本文通过短基线比较和与UTC绝对时间基准比较,验证了精密单点授时精度(RMS)优于1 ns。     

一种基于CORS的GNSS事后精密定位服务平台建设方法

针对CORS服务的通信信号盲区定位和高精度静态定位解算需求等问题,提出了一种基于Internet的数据加密推送和Bernese自动数据解算的GNSS事后精密定位服务平台建设方法,采用数据处理与用户服务分离方案,突破了并发用户请求的数量限制,并采用定位结果动态偏移及传输文件动态加密的双重加密方法,确保了信息安全。实测数据试验结果表明,平台数据处理结果精度、时效性和稳定性较好,可向用户提供厘米至毫米级GNSS事后精密定位服务。     

一种提高精密单点定位实时性的方法

由于要获取PPP需要的精密钟差文件至少有2d的时间延迟,因此通过提取IGS当天发布的超快星历中的卫星钟差数据,并对钟差数据进行插值,将插值结果做成标准格式钟差数据文件应用到PPP中,可以将精密单点定位的实时性提高为3~9h。基于Bernese软件,采用生成的钟差文件以及当天的超快星历文件对大量实测数据进行PPP。结果表明,对于4h的观测数据,该方法解算精度达到厘米级;当观测时间大于6h时,解算精度基本能够稳定在1~5cm。     

基于Bernese GPS软件的GPS数据自动解算系统的研究

针对高精度GPS数据处理软件操作的复杂性,研发出一套基于Bernese GPS的GPS站网数据自动处理系统AUTO-BGPS。简单介绍Bernese5.0的数据处理原理,着重介绍其BPE功能,阐述AUTO-BGPS自动解算系统的结构设计、功能模块及数据处理过程。通过应用实例验证该软件的可用性。     

阿克苏河-塔里木河水系水质污染遥感监测与评价

 采用Landsat TM数据分析了阿克苏河—塔里木河断面水质污染状况,通过波段的DN值和常规监测数据建立能反映水质状况的 污染物监测模型。结果发现,将2000年常规监测数据代入模型后,与遥感数据的结果基本吻合| 重建阿克苏河—塔里木河的连续水体 污染变化曲线,得出污染物浓度随着远离上游而增加。     

Monitoring drought dynamics in the Aravalli region (India) using different indices based on ground and remote sensing data

The hard-rock hilly Aravalli terrain of Rajasthan province of India suffers with frequent drought due to poor and delayed monsoon, abnormally high summer-temperature and insufficient water resources. In the present study, detailed analysis of meteorological and hydrological data of the Aravalli region has been carried out for the years 1984–2003. Standardised Precipitation Index (SPI) has been used to quantify the precipitation deficit. Standardised Water-Level Index (SWI) has been developed to assess ground-water recharge-deficit. Vegetative drought indices like Vegetation Condition Index (VCI) and Temperature Condition Index (TCI) and Vegetation Health Index (VHI) have been computed using NDVI values obtained from Global Vegetation Index (GVI) and thermal channel data of NOAA AVHRR satellite. Detailed analyses of spatial and temporal drought dynamics during monsoon and non-monsoon seasons have been carried out through drought index maps generated in Geographic Information Systems (GIS) environment. Analysis and interpretation of these maps reveal that negative SPI anomalies not always correspond to drought. In the Aravalli region, aquifer-stress shifts its position time to time, and in certain pockets it is more frequent. In comparison to hydrological stress, vegetative stress in the Aravalli region is found to be slower to begin but quicker to withdraw.     

Landslide risk analysis between Giri and Tons Rivers in Himachal Himalaya (India)

The area around Sataun in the Sirmur district of Himachal Pradesh, India (falling between the rivers Giri and Tons; both tributaries of the Yamuna River) was studied for landslide vulnerability on behalf of the inhabitants. The study was made using extensive remote sensing data (satellite and airborne). It is well supported by field evidence, demographic and infrastructural details and aided by Geographic Information System (GIS) based techniques. Field observations testify that slope, aspect, geology, tectonic planes, drainage, and land use all influence landslides in the region. These parameters were taken into consideration using the statistical approach of landslide hazard zonation. Using the census data of 1991, vulnerability of the populace to the landslide hazard was accessed. As most of the infrastructure in the region is concentrated around population centres, population data alone was used for vulnerability studies.     

Gravity Changes Before Large Earthquakes in China: 1998-2005

Although it is well known that coseismic gravity changes take place during an earthquake, previous research has not yielded convincing evidence demonstrating that significant gravity changes occur before large earthquakes. Furthermore, even if we suspect that gravity changes occur before large earthquakes, we have yet to demonstrate how to consistently observe these changes for useful earthquake forecast that would bring benefits to society. We analyzed ground gravity survey data obtained in 1998, 2000, 200...     

GNSS系统及其技术的发展研究

阐述了国际上卫星导航系统的总体发展,对美、俄、欧、中的四大全球系统,以及相关的区域系统和增强系统进行了简单的介绍,研究分析了GNSS系统及其技术的发展趋势,同时分析了我国Compass全球系统面临的机遇和挑战,并提出了我国未来工作的建议.     

“4D”技术及其应用

介绍“４Ｄ”（即数字地面模型、数字正射影像、数字栅格地图和数字线划地图）系列产品的生产流程、关键技术、及其在耕地保护、防灾减灾救灾和城市规划等方面的应用方法。     

Virtual Australia: its key elements – know,think, communicate

Abstract

Virtual Australia is not a well-defined or agreed concept. This discussion paper conceptualises Virtual Australia as a ‘virtual [digital] model containing and representing all non-trivial objects and their contextual environment – from blue sky to bedrock – in real world Australia’. It describes a scenario for Virtual Australia, one or two decades from now, in which the locations and conditions of non-trivial objects and their environment are updated automatically through a combination of remote sensing and wireless communication technologies in support of a ‘Supranet’. It then examines the concept of the ‘Supranet’ – a pervasive information network based largely on wireless technology linking the physical world to a virtual model in real time – and develops and discusses three principal characteristics of the Supranet: the ability to have or collect specific information (know); the ability to process information (think); and the ability to communicate that information. If, in the near future, any or all non-trivial devices are to some extent able to know, think and communicate, the potential for object autonomy will be realised.     

Toward seamless indoor-outdoor applications: Developing stakeholder-oriented location-based services

Location-Based Services (LBS),an emerging new business based on smartphone and mobile networks,are becoming more and more popular.Most of these LBSs,however,only offer non-seamless indoor/outdoor applications and simple applications without giving stakeholders the chance to play an active role.Our specific aim is to solve these issues.This paper presents concepts to solve these issues by expanding the Open Location Services Interface Standard (OpenLS) to allow seamless indoor/outdoor positioning and to extend the content of the services to include information recommended by stakeholders.     

地理数据库的关系模型及其实现

本文从以图论观点分析地理实体入手,系统阐述了地理数据库关系模型的设计法和过程。作者于1984年4～9月间在微型机上设计建立了关系型地理数据库的实方验系统(RGDB)。该系统采用了本文提出的关系模型,采用了可动态扩库的子库组合结构,这种结构具有灵活性和提高空间利用率的优点。RGDB含有多种功能的数据操作命令,除了具有一般检索功能外,还能进行“开窗”选取和十分“自由”的映象选取。本文对RGDB系统的主要性能和实现途径作了扼要介绍。     

GIS空间数据的采集误差及其分析

本文详细阐述了GIS数据采集过程中的误差来源，重点分析了通过地图、遥感和摄影测量等方式采集数据所产生的误差及其特性，分析了其对GIS数据的影响与消减方法。