人卫激光测距资料的压缩处理和统计分析

本文主要介绍由人卫激光测距的完整原始资料压缩生成标准点的过程，同时也对各个测站的观测资料按月进行了统计分析和精度估计。为了消除长弧解中非模型摄动所引起的系统差，我们应用了短弧和长弧定轨相结合的方法，进一步提高了解算精度。     

两种机动力建模方法的适用性分析

分析了脉冲经验力和分段线性经验力两种机动力模型在GEO卫星机动期间定轨和机动后轨道预报中的适用性,同时比较了两种机动力建模方法与短弧动力学方法之间在轨道预报方面的优劣。实验结果表明,在机动定轨中,脉冲经验力模型比分段线性模型更优越。两种机动力建模方法东西机动期间单天弧段轨道拟合精度可优于5m,但线性模型轨道预报精度比脉冲经验力模型和短弧动力学方法差。C波段观测量能够改善机动期间定轨精度。     

EOP预报误差对导航卫星轨道预报的影响分析

导航卫星轨道预报是利用精密定轨结果在惯性系下进行轨道外推，再将外推得到的惯性系轨道转换为地固系轨道，然后生成卫星星历数据。由于坐标系转换时使用的是带有误差的地球定向参数（EOP：Earth Orientation Parameters）预报值，转换结果会产生误差，进而影响轨道预报结果的精度。分析了EOP快速预报产品公报A的预报精度，研究了参数预报误差对轨道预报精度的影响。结果表明，对于利用GPS精密星历外推模拟得到的卫星轨道而言，EOP预报1天引起的轨道预报误差大致分布在0．232±0．183m，参数预报7天引起的轨道预报误差大致分布在0．438±0．356m。     

模糊度固定与弧段长度对区域站定轨的影响分析

我国北斗卫星导航系统难以实现境外全球布站,采用区域站观测值是实现高精度定轨的主要手段。本文分析了整网模糊度固定、有效定轨弧段选择对提高区域定轨精度的作用。采用陆态网GPS观测数据进行区域精密定轨仿真验证,首先论证了不同测站分布下,整网模糊度固定对区域定轨精度的效果,结果表明:相同测站条件下,固定解定轨精度比浮点解精度提高30%以上;仅采用国内7个站的固定解三维定轨精度即达到20cm左右,优于27站的浮点解精度。另外,从星座的构型与地面站分布的可视范围方面,分析了不同观测时长对定轨精度影响,实测数据论证表明:当中国区域站观测时间大于48h,总能获取不小于24h的区域有效定轨弧段,并且各卫星最佳的24h观测弧段三维定轨精度均可达到0.3m左右。     

IGSO姿态控制模式切换期间定轨策略研究

我国卫星导航系统IGSO卫星采用动态偏航与零偏航两种姿态控制模式,在太阳矢量与轨道面夹角较小时,采用零偏航。卫星姿态控制模式的切换造成了卫星所受光压力的变化。当处理包含动偏/零偏切换点的数据弧段时,由于卫星精密轨道确定策略及光压模型的不适应,无法用一组光压参数拟合两种状态,造成定轨精度下降。本文提出了利用分段线性模型描述太阳光压的定轨策略,可将定轨重叠弧段URE精度提高75%。解算的光压参数能够反映出两种状态的差异,是解决姿态转换期间轨道确定的有效方法。     

由星载GPS确定低轨卫星初始状态解的误差分析

分析了星载GPS动力学短弧定轨中的偶然误差、GPS星历误差和采样间隔对卫星初始状态参数估计结果的影响。仿真计算表明，在非力学模型误差综合影响下，利用双频P码无电离层组合进行动力学短弧定轨的精度优于10m；弧段较短时法方程严重病态，条件数高达10^9，此时宜寻求有效的算法。     

由星载GPS双差相位数据进行CHAMP卫星动力学定轨

为了确定CHAMP卫星的轨道，由星载GPS数据和IGS跟踪站的GPS数据构造星地相位双差观测量，利用EOP、SGO、时间等数据，对GPS数据进行预处理，包括钟差改正、模糊度解算和周跳探测、卫星姿态改正、天线偏差和相位中心改正等，采用CHAMP卫星受力摄动模型，根据动力学原理，对CHAMP卫星进行实际定轨。与德国GFZ定轨结果PSO相比，本方法定轨结果径向精度为0．2857m。对于1d的重叠轨道，径向轨道差异的RMS为0．0958m。对于轨道端点比较，径向轨道差异平均为0．0666m。     

对ETALON卫星的精密定轨研究

ＥＴＡＬＯＮ卫星是１９８９年发射的激光卫星，具有正球形、高质面比和轨道近圆等特点。其轨道倾角６５°，半长径为２．５万ｋｍ。其轨道不仅稳定，而且优化了覆盖欧亚大陆及太平洋地区的几何特性，适合于测定地球自转参数，更适合于全球测地和地壳运动的研究。本文研究了对Ｅ－ＴＡＬＯＮ卫星精密定轨的要求，如摄动模型的选取，数值积分中积分步长的选取等，利用１９９４年１０月ＥＴＡＬＯＮ－２的资料，对ＥＴＡＬＯＮ－２卫星进行了精密定轨，一个月（３１ｄ）弧长的定轨精度优于１０ｃｍ，１０天弧长定轨精度优于５ｃｍ。     

ΔVLBI用于“嫦娥一号”地月转移轨道段定轨及EOP解算

推导了基于相对论时空理论的"嫦娥一号"地月转移轨道段差分VLBI(ΔVLBI)的数学模型,在此基础上利用"嫦娥一号"实测的VLBI时延观测量和模拟的河外射电源时延观测量组成了ΔVLBI时延观测量,在参数最优先验精度下解算了不同弧段长度的"嫦娥一号"轨道及地球定向参数(EOP)等未知参数,并根据各参数的解算精度及外符合程度确定了最优观测弧段长度,并分析了该条件下的参数解算精度。     

单中继星单低轨卫星的联合定轨精度分析

针对由单中继星和单低轨卫星组成的联合定轨系统,给出了系统内不同轨道卫星摄动项的选取方案和卫星间的可见性判别模型。在模拟出含有白噪声的四程测距观测数据文件的基础上,研究了测距精度和采样弧段对联合定轨中高、低轨卫星定轨精度的影响。得出如下结论：联合定轨更有利于对低轨卫星的轨道改进;同样的采样时间条件下,测距噪声越小定轨精度越高,并且采样时间越短它的影响越明显;同样的测距噪声条件下,所用资料的采样时间越长精度越高,但当测距精度很高时,TDRS达到最好定轨精度所需的采样时间相应有所缩短。并在定出轨道后进行了轨道预报,分析了轨道预报的趋势及精度。     

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。