北斗CORS实时动态差分定位精度实验分析

目前,兼容北斗导航卫星系统(BDS)的中山市连续卫星定位服务系统(ZSCORS)已经建成,分析ZSCORS环境下的BDS、GPS、BDS/GPS的实时动态差分定位精度很有必要。本文选择12个C级GPS控制点进行精度测试,分别采集BDS、GPS及BDS/GPS组合信号观测值,并进行统计分析,在ZSCORS实时动态差分定位环境下,BDS精度与GPS相当,BDS/GPS组合精度和效率明显高于BDS、GPS。     

CNS+GNSS+INS船载高精度实时定位定姿算法改进研究

天文导航（CNS）、卫星导航（GNSS）和惯性导航（INS）3种系统组合可提供高精度的定位定姿结果。实际工程中因INS长时间误差累积，以及系统硬件传输存在不可忽略的时间延迟，导致INS提供给CNS的预报粗姿态误差较大，恶劣海况下难以保障快速搜星，造成天文导航可靠性下降、姿态测量精度较低的问题。为此，本文提出了一种CNS+GNSS+INS高精度信息融合实时定位定姿框架，引入了等角速度外推措施，有效地解决了惯导信息延迟问题。通过高精度转台模拟恶劣海况下载体大角速度摇摆，验证了本文提出的改进算法的有效性。试验结果表明，该算法架构简单，性能可靠，显著提高了恶劣环境下星敏感器的快速、准确搜星能力，保障了三组合姿态测量的精度和可用性。     

基于惯导／天文高精度定姿方法

研究了利用惯性导航系统与天文导航系统进行组合定姿的方法,构造了惯导/天文组合导航系统的状态方程和量测方程;采用卡尔曼滤波技术设计了惯导/天文组合定姿算法.设计飞行器的典型飞行轨迹,通过数学仿真对该算法的有效性进行了验证.结果表明,天文导航能够有效地补偿惯性导航因陀螺漂移带来的误差,非常适用于飞行器的高精度定姿.     

基于惯导/天文高精度定姿方法

研究了利用惯性导航系统与天文导航系统进行组合定姿的方法;构造了惯导/天文组合导航系统的状态方程和量测方程;采用卡尔曼滤波技术设计了惯导/天文组合定姿算法。设计飞行器的典型飞行轨迹,通过数学仿真对该算法的有效性进行了验证。结果表明,天文导航能够有效地补偿惯性导航因陀螺漂移带来的误差,非常适用于飞行器的高精度定姿。     

顾及组合导航闭环反馈的变分贝叶斯自适应滤波优化算法

多传感器组合的方式可以较好地应对全球导航卫星系统信号被遮挡、干扰等情况下的导航定位问题,滤波方法是导航定位中将多源数据融合最常使用的方法之一。在滤波过程中,组合导航的系统噪声和量测噪声无法实时精确地测定,常通过自适应滤波的方法进行时间更新和量测更新的平衡解算。贝叶斯自适应滤波方法在很多时候具有较好的效果,但是和其他的自适应滤波方法一样,该类方法都需要进行自适应因子的选取。本文根据组合导航对于实时性要求及其闭环反馈的特殊性,在变分贝叶斯自适应滤波的基础上进行了算法的优化,给出了一种调节因子的动态计算方法,并以GNSS和惯性导航系统组合系统为例,通过模拟和实测试验进行验证。试验结果表明,本文算法不需要通过迭代计算的方法就可以获取高精度组合结果,提升了计算效率;对于真实的动态场景中,本文算法的调节因子动态自适应确定,结果更具有优越性。     

GNSS PPP/INS紧组合定位测速性能分析

针对动态高精度定位测速的问题,该文对卫星导航与惯性导航系统的数学模型进行研究,采用扩展卡尔曼滤波的处理方法,实现了GNSS PPP/INS紧组合的定位测速算法。利用实测数据验证本文实现的紧组合算法,并对BDS、GPS与GPS+BDS单频、双频观测值与INS紧组合的定位性能进行分析。结果表明:GNSS PPP/INS紧组合定位测速精度在动态开阔环境下优于PPP定位测速精度,对定位结果有1%～70%不同程度的改善,对测速结果则有一个量级的提升,平面测速精度在1(cm·s~(-1))左右,高程测速精度达到亚厘米级。     

BDS/GPS/GLONASS融合网格伪距差分定位性能分析

为了充分利用全球导航卫星系统资源,最大限度发挥北斗卫星导航系统的优势,向用户提供高精度、高可靠性和稳定性更好的服务,该文对BDS/GPS/GLONASS 3系统融合网格伪距差分定位性能进行了分析。运用该文阐述方法的原理进行实验分析,结果表明,3系统融合网格伪距差分定位较其他方案具有更高的定位精度、解算成功率,可见卫星数大幅度提高,可靠性和稳定性更优。     

异步联邦UKF的GNSS／SINS／摄影定位组合导航算法仿真

在飞行器进近过程中,为了提高组合系统的导航精度,针对传统联邦滤波器对非线性系统模型易导致滤波发散问题.分析了两种导航方式的优缺点,提出了基于卫星导航／惯性导航／摄影测量(GNSS／SINS／Photogrammetry)的组合导航联邦滤波算法,并推导了系统误差模型.该算法取长补短利用联邦无迹卡尔曼滤波器将GNSS定位和摄影定位、定姿精度高的优势对SINS进行在线误差估计.针对多传感器非等间隔数据采样问题,采用时间与量测更新分离的异步非等间隔联邦滤波算法进行信息融合,并对滤波器结构进行改进以减少算法复杂度.仿真实验证明基于联邦UKF的组合导航系统较传统联邦滤波算法位姿精度有明显的提高,且系统鲁棒性也有一定的增强.      

双源车载差分卫星导航定位稳定性分析

车载卫星导航系统广泛应用于交通时,采用伪距单点定位就可以满足日常驾驶需要,如需进一步提高导航精度就要利用伪距差分技术进行实时车载导航定位,采用单频三差相位平滑伪距观测值,导航精度在2m以内,可进行车道级导航定位。提出了用单频三差码相组合二次差为标准对三差平滑进行质量控制,以减小周跳和粗差的影响。分析了车载卫星差分导航过程中北斗系统和全球定位系统卫星的可见性,通过在算法中实现北斗和全球定位系统联合解算,以增加车载导航的稳定性。     

北斗系统载波相位动态差分定位方法

针对北斗系统高精度动态差分定位解算不够快速准确等问题,该文介绍北斗导航卫星系统载波相位动态差分定位方法:利用B1、B2载波相位观测值组成双差宽巷载波相位观测值,进行双差宽巷组合观测值整周模糊度的确定,然后解算双差载波相位观测值的整周模糊度,利用载波相位观测值进行动态定位解算;并通过BDS实测数据进行算法验证,证明本文解算的方法可以实现BDS高精度差分定位的整周模糊度动态解算,得到测站的厘米级差分定位结果。     

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。