基于伪距相位和STPIR组合的北斗三频周跳探测与修复

GNSS周跳探测中,电离层残差法的适用性受数据采样间隔的影响较大,同时联合其它组合观测量进行周跳修复时,周跳修复方程组易出现病态解。针对这些问题,文中提出一种可靠的北斗三频周跳探测与修复算法,通过构造北斗三频电离层残差组合观测量,进行二阶历元间差分,基于三频伪距相位组合优选理论,选取适用于北斗三频数据的伪距相位组合,结合两种组合观测量,优选条件数较小的组合系数矩阵进行周跳修复,最后通过北斗三频实测数据验证,结果表明:在数据采样间隔较大的情况下,利用构建的三个组合观测量可以探测出北斗三频原始数据中的所有周跳,具有很好的修复效果。     

几种周跳探测方法的研究分析

周跳是影响基线解算精度的一个重要因素。从周跳探测方法的基本原理出发,利用实测数据详细研究分析高次差法、相位减伪距法和电离层参差法3种周跳探测方法的特点。分析结果表明,电离层残差法适合小周跳的探测,相位减伪距法和高次差法适合大周跳探测,且前者探测效果更佳;为更好地完成周跳探测需将多种方法组合使用。研究结果有助于提高GPS基线解算精度,便于进行相应软件开发。     

北斗三号卫星的周跳探测与修复算法

在高精度GNSS应用中,载波相位观测值中出现周跳问题直接影响到整周模糊度的解算及最终定位精度,针对北斗卫星导航系统三代卫星密集发射的现状,该文提出一种联合采用码伪距与相位伪距组合、MW组合和电离层残差组合进行北斗三号卫星双频数据周跳探测和修复的算法。该算法可以发挥单个组合优势有效进行周跳探测且能避免各自的探测盲区,联合3种组合观测量进行周跳值求解时,计算方法简单,可以直接取整得到周跳值。通过对北斗三号卫星双频实测数据的处理分析,验证了该算法能够准确地探测出所有周跳,并能够有效修复。     

联合法探测修复北斗系统测量数据周跳

准确探测周跳并进行修复是提高北斗系统导航定位精度的核心问题之一,针对电离层残差法可以高效地探测小周跳但却无法修复周跳与无法正常探测出某些特定组合的周跳,以及多普勒积分法并不完全适用于北斗系统高轨卫星的周跳探测与修复等缺陷,提出了基于电离层残差法和多普勒积分联合探测修复周跳的方法,并应用实测数据进行了算例验证。     

BDS/GPS双频三差组合周跳探测与修复方法研究

针对BDS/GPS双差组合数据解算需要考虑观测数据周跳探测与周跳修复能力的问题,研究组合观测值周跳检测量公式模型,给出一种能够有效探测并修复周跳的BDS/GPS双频三差组合周跳探测与修复方法。实验数据结果表明,该方法利用三差后的无电离层组合残差和双频载波残差平均值做为周跳检测量从而能够有效探测出GPS卫星和北斗的GEO、MEO、IGSO卫星观测值中存在的周跳并修复,从而为BDS/GPS双差网解提供高质量、高可靠性的观测数据。     

惯性辅助强多径环境中的北斗三频周跳探测与修复

针对北斗三频信号,引入了惯性信息辅助周跳探测与修复,建立了北斗/INS松组合模型,提高了多径误差严重影响下的BDS周跳探测成功率和修复率。在常规伪距-相位组合与几何无关组合探测三频周跳的基础上,提出了INS定位辅助的北斗三频组合法,构建了INS辅助的周跳决策量,分析了INS定位误差对周跳探测的影响。该方法克服了周跳探测受伪距观测值精度影响的不足,实现了北斗系统多径环境中的小周跳探测。试验采用船载INS/BDS三频组合系统进行数据实测分析,结果表明,在水面强多径噪声环境导致传统三频探测模型失效的情况下,该方法显著提高了探测成功率与修复率,并适用于低频北斗观测数据。     

GNSS三频周跳探测与修复算法

针对使用组合观测值探测周跳存在不敏感周跳且难以修复的问题,研究了三频周跳探测与修复的几何原理,从几何角度研究了多个相位无几何组合(GF)探测周跳的异同,以及加入MW组合后的效果,并搜索了相应的不敏感周跳。提出了以对应的横截面积最小为原则选取组合量的方法。经北斗三频实测数据验证,GF组合的数量以两个为宜,加入MW组合后不敏感周跳进一步减少,优化选取的两个GF组合和MW组合联合探测周跳仅存在一个不敏感周跳,且探测到的周跳均能正确修复。     

北斗与GPS双系统测姿研究

在研究既有算法的基础上,编程实现使用北斗数据求解载体的三姿态角,并通过与同源GPS数据解算结果对比分析,利用统计方法得到北斗数据解算结果的精度、稳定性和控制粗差能力等信息。为了验证试验结果,选择不同时段、不同地点进行了3次重复试验,结果表明,北斗系统在载体姿态应用中具有较高的精度和稳定度,在一些情况下甚至优于GPS系统。算法上,本文采用卡尔曼滤波进行基线解算,LAMBDA算法求解整周模糊度,能够达到高精度的在航解算能力。     

高频GNSS数据MGF周跳解算方法的质量控制

针对全球导航卫星系统（global navigation satellite system, GNSS）高频数据周跳的高可靠性快速探测与修复,基于改进的相位几何无关(modified geometry-free, MGF)组合量,提出了MGF周跳解算的质量控制方法,以进一步提高周跳修复的成功率。根据MGF组合观测量及误差特征,推导了其周跳修复的边界条件,并分析了不同导航卫星系统MGF方法的适用性,及观测噪声对周跳解算结果的影响。在此基础上,构建了MGF组合的质量控制检验量,经多系统GNSS实测数据试验分析,结果表明:MGF方法能够对小周跳（如小于5周的周跳）实现快速探测,修复成功率可达到99.90%以上;利用MGF组合的质量控制检验量能够分别识别出GPS、BDS和GLONASS中100%、87.57%和77.42%的错误周跳解算结果,使得MGF周跳解算错误率降低至0.01%。MGF方法受相位噪声影响显著,MGF组合的质量控制检验量能够有效识别错误的周跳解算结果,从而提高周跳修复成功率,但随着相位几何无关组合量噪声水平的增加,MGF质量控制检验量对于周跳修复错误和观测噪声的区分性降低。     

三频观测量线性组合在北斗导航中的应用

随着导航卫星定位系统多个频率的逐步应用,将多频组合观测值的一些组合特性应用到周跳、粗差的探测修复及加快模糊度的解算已成为必然趋势。三频观测量线性组合的主要目的是为了增强周跳的探测和加快模糊度解算,减少电离层和观测噪声的影响。在分析北斗三频组合观测量特性的基础上,给出了一些有用的三频观测量组合。     

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.     

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。     

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。