GPS/COMPASS组合变形测量性能分析

GNSS系统的定位精度和可靠性在很大程度上依赖于观测到的卫星数量和几何图形分布.在城市、露天矿区和峡谷等地区,由于可观测卫星数少,单一系统的定位精度往往难以满足要求,GNSS多星座组合是解决问题的一个有效措施.选取雅砻江卡拉电站滑坡监测网中的一个监测点,利用实测的COMPASS星历和GPS卫星星历,从可见卫星数目及GDOP值两个角度,对GPS、COMPASS单星座系统以及其组合系统变形测量性能进行了对比分析.实验表明GPS和COMPASS组合系统能够有效改善变形监测精度.     

地基GNSS电离层层析方法及应用

随着GALILEO、GLONASS和BDS等系统的快速发展,全球导航卫星系统GNSS(Global Navigation Satellite System)为电离层层析技术的应用带来大量的观测数据,可弥补单星座条件下地面观测站点少和观测视角有限等不足。本文利用多星座GNSS的观测数据,通过融合定权的方式,提出一种基于地基GNSS的电离层层析方法,求解出高精度的电离层电子含量值。利用该方法反演出欧洲区域上空的电子密度。实验结果表明,多星座GNSS反演的精度要优于使用单GPS数据的结果。并将该方法应用到磁暴探测中,与垂测仪的观测结果进行比较,验证了多星座GNSS电离层层析方法的可行性和优越性。     

多GNSS监测下中国区域电离层格网模型可用性分析

多系统全球卫星导航系统(GNSS)的出现为天基增强系统(SBAS)电离层格网模型的性能提升提供了可能,但多系统GNSS测量对电离层格网模型性能提升是有条件的. 为此,利用中国区域GPS观测模拟分析了多系统GNSS测量对中国区域电离层格网模型可用性的影响. 结果表明:多系统GNSS测量可有效提高电离层格网模型的覆盖范围. 中国南方地区存在低纬赤道电离异常(EIA)现象,严重影响SBAS电离层格网模型实现性能,单纯增加GNSS测量不能有效应对低纬电离异常现象影响. 中国北方地区电离层延迟变化平缓,在多系统GNSS测量情况下可以考虑减少地面监测站数量,仍能保持系统原有性能.      

全球导航定位系统GNSS的技术与应用

介绍了GNSS系统的发展过程及组成部分（GPS,GLONASS,GALILEO,BEIDOU）,归纳了GNSS定位、GNSS—R、GNSS掩星、组合导航、嵌入式等技术,并对GNSS最新的应用领域进行全面研究分析,以及预测GNSS系统的发展前景。     

多系统融合全球电离层建模研究

近年来,我国BDS的建设和应用为GNSS电离层研究带来了新的机遇和挑战。本文采用中国测绘科学研究院i GMAS分析中心数据,构建了三系统融合全球电离层球谐函数模型,并对结果进行分析。研究表明:除去精度较差的海洋区域,在大陆地区,多系统融合全球电离层建模结果能较精确地表达电离层VTEC;对比三系统差分码偏差DCB的精度统计结果,GPS卫星系统C1P2码偏差均小于1 ns,大部分在0.5 ns以内,精度最高;GLONASS卫星系统C1P2码偏差均小于2 ns,精度比GPS系统略低;BDS卫星系统B1B2码偏差均小于1 ns,精度比GLONASS系统略高,但不如GPS系统稳定,码偏差随年积日变化较大,可能是BDS系统星座结构不完善的原因。     

GPS／BDS／GALILEO多系统融合伪距单点定位性能分析

针对在不同截止卫星高度角的情况下,GPS、BDS、GPS／BDS、GPS／GALILEO、BDS／GALILEO 、GPS／BDS／GALILEO间伪距单点定位精度的差异,本文对多系统融合伪距单点定位的数学模型和误差项处理方法进行了研究,以香港CORS站HKMW站点全天的数据为实验数据,在截止卫星高度角10°、15°、20°、30°、40°的情况下,进行了GPS、BDS、GPS／BDS、GPS／GALILEO、BDS／GALILEO、GPS／BDS／GALILEO伪距单点定位解算。结果表明,GPS／BDS／GALILEO组合系统在X、Y、Z各方向的定位精度都优于单系统,定位结果更加稳定,尤其在截止高度角达到30°、40°时,单系统的定位精度急剧下降,历元可用率降低,而GPS／BDS／GALILEO组合系统仍能满足定位的要求。      

GPS/GALILEO组合系统可见卫星与GDOP的区域和时序分析

卫星星座方案的选择对导航定位精度具有很大影响。本文根据GALILEO系统的设计轨道参数模拟得到的GALILEO系统的卫星位置,分别计算了GPS系统、GALILEO系统和GPS/GALILEO组合系统在不同卫星截止高度角的情况下,全国范围内可见卫星和GDOP值的分布情况,并选择了北京、武汉和乌鲁木齐三个城市,连续观测24小时,分析了各城市的可见卫星和GDOP值随时间的变化规律。     

港珠澳大桥岛隧工程GNSS数据电离层延迟分析

利用IGS发布的最终电离层数据,分析了在港珠澳大桥岛隧工程区域经度(约E 114°)不同纬度的VTEC分布特征,并以电离层延迟为评价指标,采用TEQC软件对港珠澳大桥岛隧工程实测的GNSS数据进行了数据质量分析,得到结论:北半球沿114°E经线,纬度越低,VTEC日变化量越大,VTEC值越高;低纬度VTEC值在GPS时3~12h显著高于中高纬度;VTEC年变化量季节性特征明显;实测GNSS数据,多颗卫星的电离层延迟峰值超过20m,电离层延迟大于GNSS测量中的一般水平。     

基于STK的全球卫星导航定位系统DOP值仿真

通过STK卫星数据库建立了GPS卫星星座;根据GALILEO卫星设计参数,利用轨道向导建立GALILEO卫星星座。比较了武汉地区GPS、GALILEO、GPS和GALILEO组合的卫星可见数和GDOP值,以及全球GDOP值的分布。     

GNSS全球广播电离层模型精度分析

单频用户主要采用全球导航卫星系统(global navigation satellite system,GNSS)广播电离层模型来修正电离层延迟,GPS、Galileo和BDS-2均播发广播电离层参数。BDS-3试验卫星也播发了应用于全球电离层延迟修正的BDGIM(BeiDou global ionospheric delay correction model)模型参数。以国际GNSS服务(International GNSS Service,IGS) GIM (global ionosphere maps)产品和全球140余个GNSS观测站GPS双频观测量为基准,从全球范围、不同纬度、不同区域等系统分析了GPS、Galileo和BDS-3的全球广播电离层模型改正精度,并与IGS预报电离层产品(IGS P1和IGS P2)进行比较。分析认为,IGS P1和IGS P2产品的改正精度总体最优,BDGIM参数优于Gal NeQuick和GPS K8。对于BDS-3新发布的BDGIM参数,分析认为,在全球范围的改正精度(均方根)约为3.58 TECU,改正率约77.2%,在全球不同区域的改正精度相当。     

基于OSG的火星形貌3维建模与绘制

开展了基于开源3维渲染引擎OSG(OpenSceneGraph)的火星形貌3维建模与绘制的研究.使用地形数据库创建工具VPB(VirtualPlanetBuilder)创建了整个火星的分页数据库,并利用基于OSG的仿真平台实现了火星形貌数据的3维可视化.实验结果证明,该方法能很好地处理海量地形数据,完成火星形貌的3维重...     

三重加权变形监测预测模型及应用

针对GM(1,1)建模过程存在背景值、时间因素和初始条件3方面的不足,该文提出三重加权TPGM(1,1)预测模型。通过对背景值进行加权生成新的背景值,建立PGM(1,1)模型;在PGM(1,1)基础上考虑到时间因素,在求解灰参数时进行第2次加权建立DPGM(1,1)模型;最后考虑到初始条件对预测模型的影响,在DPGM(1,1)基础上进行第3次加权,建立TPGM(1,1)模型。通过实例分析,比较GM(1,1)、PGM(1,1)、DPGM(1,1)、TPGM(1,1)4种模型在变形监测数据处理中的拟合和预测结果,表明三重加权TPGM(1,1)模型拟合效果更好、预测精度更高;该模型具有前3种模型的优点,同时弥补了传统GM(1,1)存在的不足。     

Retrieval of effective leaf area index (LAIe) and leaf area density (LAD) profile at individual tree level using high density multi-return airborne LiDAR

As an important canopy structure indicator, leaf area index (LAI) proved to be of considerable implications for forest ecosystem and ecological studies, and efficient techniques for accurate LAI acquisitions have long been highlighted. Airborne light detection and ranging (LiDAR), often termed as airborne laser scanning (ALS), once was extensively investigated for this task but showed limited performance due to its low sampling density. Now, ALS systems exhibit more competing capacities such as high density and multi-return sampling, and hence, people began to ask the questions like—“can ALS now work better on the task of LAI prediction?” As a re-examination, this study investigated the feasibility of LAI retrievals at the individual tree level based on high density and multi-return ALS, by directly considering the vertical distributions of laser points lying within each tree crown instead of by proposing feature variables such as quantiles involving laser point distribution modes at the plot level. The examination was operated in the case of four tree species (i.e. Picea abies, Pinus sylvestris, Populus tremula and Quercus robur) in a mixed forest, with their LAI-related reference data collected by using static terrestrial laser scanning (TLS). In light of the differences between ALS- and TLS-based LAI characterizations, the methods of voxelization of 3D scattered laser points, effective LAI (LAIe) that does not distinguish branches from canopies and unified cumulative LAI (ucLAI) that is often used to characterize the vertical profiles of crown leaf area densities (LADs) was used; then, the relationships between the ALS- and TLS-derived LAIes were determined, and so did ucLAIs. Tests indicated that the tree-level LAIes for the four tree species can be estimated based on the used airborne LiDAR (R² = 0.07, 0.26, 0.43 and 0.21, respectively) and their ucLAIs can also be derived. Overall, this study has validated the usage of the contemporary high density multi-return airborne LiDARs for LAIe and LAD profile retrievals at the individual tree level, and the contribution are of high potential for advancing forest ecosystem modeling and ecological understanding.     

Review on InSAR based displacement monitoring of Indian Himalayas: issues,challenges and possible advanced alternatives

Natural and man-made disasters like earthquakes, landslides, avalanches, unplanned mining are some of the most serious factors responsible for earth surface displacement. These incidences can be harmful for the society due to loss of life and also threatful for future urban development. Therefore, continuous monitoring of disasters in terms of displacements is of fundamental importance in a modern well-organized society to understand its effects on the social and economic fabric. Availability of SAR data has been proved to be an excellent source for estimation of surface displacements with high accuracies. However, in India, SAR interferometry-related displacement measurement has still not gained appreciable momentum. More rigorous research needs to be carried out for the efficient use of this new generation technique. This review article is an attempt to discuss the issues related to SAR-based displacement studies so far conducted on Indian Himalayan region and possible advanced alternatives.     

从GPS推算大气水汽的误差分析

讨论了从GPS观测数据推算大气水汽值的各种误差，分析了这些误差对大气水汽值的影响。     

Low-low satellite-to-satellite tracking: a comparison between analytical linear orbit perturbation theory and numerical integration

Low-low satellite-to-satellite tracking (ll-SST) range-rate observations have been predicted by two methods: one based on a linear perturbation theory in combination with the Hill equations, and one based on solving the equations of motion of two low-flying satellites by numerical integration. The two methods produce almost equivalent Fourier spectra of the range-rate observations after properly taking into account a few resonant terms. For a typical GRACE-type configuration, where the two satellites trail each other at a distance of 300 km at an altitude of 460 km, and in the presence of the EGM96 gravity field model, complete to spherical harmonic degree and order 70, the agreement between the Fourier spectra is about 1 mm/s compared to a root-mean-square (RMS) value of more than 220 mm/s for the range-rate signal. The discrepancy of 1 mm/s can be reduced significantly when not taking into account perturbations caused by the J₂ term. Excluding the J₂ term, the agreement between the two methods improves to 0.4 mm/s compared to a RMS value of 6 mm/s for the range-rate signal. These values are 0.01 and 2.3 mm/s when ignoring the spectrum for frequencies below two cycles per orbital revolution, reducing the discrepancy even further to about 0.5% of the signal. The selected linear perturbation theory is thus capable of modeling gravity field induced range-rate observations with very high precision for a large part of the spectrum.     

基于非参数回归的交通事件影响范围预测

基于非参数回归方法,创新性地利用拥堵信息建立模式库,解决了传统分类、回归、神经网络等预测方法的事件特征选取限制及训练样本不足等问题,提高了预测结果的准确性。     

浅谈基于ADS80数据在像素工厂中制作正射影像的流程

像素工厂是当今世界一流的遥感影像自动化处理系统,集成自动化、并行处理和开放的架构,可以自动处理多种传感器的海量数据,生产各种制图终端。本文结合实际生产介绍了像素工厂批量生产数字地表模型(DSM)和正射影像的关键技术及工艺流程。     

基于高斯过程的高分辨率遥感图像变化检测

本文首先通过理论分析,探讨了高斯过程分类器在高分辨率遥感图像变化检测应用中的优势与不足,并针对高斯过程分类器的不足给出了相应的解决方法;其次,提出了一种基于空间上下文相关的高斯过程变化检测方法;最后,通过多个高分辨率遥感实验数据集上的实验设计与分析,验证了高斯过程分类器在高分辨率遥感图像变化检测中的应用能力,并证明了本文提出的解决方法的有效性.     

黑龙江省位置服务中心建设与服务模式探讨

对黑龙江省位置服务现状进行了分析,提出了建立的黑龙江省位置服务中心的框架。位置服务中心的建立是以手机、PDA及各种移动手持终端定位服务、车辆监控等为主的服务体系,并通过WMS方式对外提供地图服务。文中对位置服务中心的设计理念、体系结构及服务模式进行了详细描述,并对其具体应用进行了探讨,最后对未来3G时代位置服务中心的应用前景进行了展望。