GPS对流层延迟改正模型及其InSAR应用研究

分析对样本点与待插值点间水平距离和高差赋予不同影响因子的改进反距离加权内插法(IIDW)。试验表明,改进的反距离加权内插法在GPS对流层内插方面内插精度优于传统反距离加权内插法,但是在将内插值应用到InSAR干涉图对流层延迟时,高程差对对流层延迟的影响却很小。     

基于多项式拟合的移去恢复法求解对流层天顶延迟的研究

本文针对基于区域GPS网内插流动站对流层天顶延迟(ZTD)时存在的问题,提出了基于多项式拟合的移去恢复法。该方法利用对流层天顶延迟与高程之间的强相关性,通过多项式拟合将对流层天顶延迟中与高程相关的信息移去后再进行内插求解。采用SCIGN的GPS数据进行实验,结果表明:基于多项式拟合的移去恢复法的插值精度明显高于传统的反距离加权直接内插法,特别对于高程明显偏离参考站总体高程的流动站具有较好的改进效果。     

基于多项式拟合的移去恢复法求解对流层天顶延迟的研究

本文针对基于区域GPS网内插流动站对流层天顶延迟(ZTD)时存在的问题,提出了基于多项式拟合的移去恢复法.该方法利用对流层天顶延迟与高程之间的强相关性,通过多项式拟合将对流层天顶延迟中与高程相关的信息移去后再进行内插求解.采用SCIGN的GPS数据进行实验,结果表明:基于多项式拟合的移去恢复法的插值精度明显高于传统的反距离加权直接内插法,特别对于高程明显偏离参考站总体高程的流动站具有较好的改进效果.     

面向大高差RTK的对流层延迟改正模型及实时差分服务构建

在大高差区域,实时动态定位(real time kinematic, RTK）的站间对流层延迟差异较大,传统的RTK算法忽略站间大气延迟误差,严重影响定位精度。无论是全球还是中国范围,大高差地形都广泛分布,研究大高差RTK十分必要。由于对流层延迟参数与高程参数强相关,RTK中无法实时估计对流层延迟,引入外部模型是大高差RTK中修正对流层延迟误差的唯一手段。分析了大高差RTK对对流层延迟模型的特殊需求,总结了可用的经验对流层延迟模型。为进一步提高大高差RTK的定位精度,提出了基于连续运行参考站和气象站的实时实测对流层延迟模型构建方法。两种方法虽然能够提高RTK精度,但都存在各自的缺陷,未来需要进一步研究。在此基础上,提出了基于因特网航海无线电技术委员会传输协议的小区域大高差RTK服务方法,实现了RTK用户的对流层延迟无感改正。     

GPS网络RTK中对流层延迟分析

分析了网络RTK中基准站和流动站间气象元素、基线长度、高程差异和模型差异等因素对对流层延迟误差的影响,得出气象元素的大小和基线长度等与单差对流层延迟之间存在线性关系,由基准站和流动站的对流层模型差异造成的差值与高差之间也存在线性关系,且利用网络RTK内插法只可消除其中大部分的误差。这对利用网络RTK算法生成流动站的误差改正数具有重要的参考价值。     

GPS网络RTK中对流层延迟分析

分析了网络RTK中基准站和流动站间气象元素、基线长度、高程差异和模型差异等因素对对流层延迟误差的影响,得出气象元素的大小和基线长度等与单差对流层延迟之间存在线性关系,由基准站和流动站的对流层模型差异造成的差值与高差之间也存在线性关系,且利用网络RTK内插法只可消除其中大部分的误差.这对利用网络RTK算法生成流动站的误差改正数具有重要的参考价值.     

对流层延迟改正内插方法的比较

对GPS获取的大气延迟改正加密内插的三种方法进行了简述与比较。并通过算例分析,得出从GPS观测值中获得的对流层延迟改正的双差分数据,采用距离反比加权内插法(IDW)和克里金内插法(Kriging)插法是比较有效的。     

一种区域实时对流层内插模型及其在PPP中的应用

利用反距离加权内插法,对基准站解算的天顶对流层延迟（ZTD）建立了区域实时ZTD模型,评估了该模型内插流动站对流层延迟对PPP定位精度和收敛时间的影响。试验表明：与传统ZTD采用参数估计的处理方法对比,二者解算得到的PPP精度在水平方向上效果相当,但在垂直方向上,模型内插对流层解算的定位精度提高约为5 cm,且能显著提高PPP收敛速度。说明应用本方法建立非气象参数的区域天顶对流层延迟模型能有效加快PPP的收敛速度,且提高定位精度。     

对流层经验改正模型在中国区域的精度评估

对流层延迟是全球导航卫星系统(GNSS)计算的主要误差之一,其模型精度对测站坐标解算有较大影响,在高程方向尤为明显。因此,有必要对不同的对流层延迟改正模型的适用性进行评估。采用SHA解算了中国陆态网GNSS跟踪站的对流层天顶延迟数据,对常用的对流层改正模型EGNOS/UNB3m/GPT/GPT2的天顶延迟量在中国不同区域、不同季节的适用性进行了分析。结果显示,4种模型的RMS均为4~5cm,各模型RMS之差小于1cm,其中GPT2模型的RMS最小;4种模型的平均偏差(BIAS)为1cm左右,GPT2模型的BIAS最大,为1.5cm;时间上,各个模型在夏季精度普遍较低,这是因为夏季水汽丰富,对流层湿延迟变化较大;空间上,各模型在东南沿海精度较低,因为东南沿海气候湿润,湿延迟变化较大;各模型精度对测站高程不敏感,精度在比较高的测站并无明显降低。通过对不同模型在中国区域的精度分析,验证该改正模型可以为中国区域用户的对流层模型的选择提供一定的参考。     

三种对流层延迟模型的精度对比

针对不同对流层延迟模型的改正精度不同的问题,该文采用3个IGS站BJFS、SHAO、WUHN的2014年对流层天顶总延迟数据以及地面气象数据,对目前常用的3种对流层延迟模型:霍普菲尔德(Hopfield)、萨斯塔莫宁(Saastamoinen)、欧洲地球静止导航重叠服务(EGNOS)的精度进行了分析。结果表明:Saastamoinen和Hopfield模型的精度相当,EGNOS模型精度略差于其余两种模型,但能满足GNSS米级的定位要求;在气象条件变化剧烈时,EGNOS模型精度不如实测地面气象数据的Hopfield和Saastamoinen模块。     

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.     

使用FME与VBA提取机场方格网高程数据

因受机场工程设计软件的测量数据容量限制,基于LiDAR采集、点云分类后得到的地面点云数据LAS不能完整应用于目前设计软件进行设计计算。本文通过对拟选技术方案的筛选,提出了利用FME Workbench数据处理功能,结合VBA编程获取外部方格网平面数据的方法。该方法在FME Workbench中实现了地面点云数据构建TIN、采用逐点内插方法从TIN中提取方格网高程数据、等高线生成及相应图形处理与成果输出。最终通过实际算例证明了该方法的有效性。     

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.     

自动车辆定位导航系统中传感器的误差分析

对国界定位导航系统中几种常见的辅助传感器所产生的误差进行了分析，导出了不同传感器的误差模型。这些误差模型是估计车辆位置的扩展卡尔曼滤波器的基础，同时也为选择适当的传感器提供了理论根据。