Semi-dynamical Doppler satellite positioning

In semi-dynamical satellite geodesy, the satellite orbit is determined beforehand by dynamical methods, and tracking station coordinates are determined geometrically from satellite observations and the accepted satellite coordinates. This paper analyzes the use of the U.S. Navy Navigational Satellite Doppler (formerly Transit) system in the semidynamical mode, presenting some test network numberical results. Three error sources are considered: errors in the satellite coordinates, refractive errors on the Doppler observations, errors contributed by the tracking receivers. Compensatory techniques are discussed, such as relaxing the satellite orbit, ionospheric and tropospheric refraction reductions, tracking receiver time recovery, translocation.     

Present limitations of accurate satellite Doppler positioning for tectonics. An example: Djibouti

One of the possibilities of the Doppler positioning from satellite is to provide geodetic measurements continuous in time without the need for reference stations. If measurements of sufficient accuracy can be achieved they may be used to study local surface displacements in relation to tectonic activity. A Doppler receiver of the MEDOC network is located near Djibouti in the Ghoubhat-Asal rift region which corresponds to the accreting plate boundary between the Arabian and African plates. In November 1978, a seismic and volcanic crisis occured in this area. Surface geodetic measurements and levellings performed in 1973 and 1978–79, just after the crisis, reveal a 60–80 cm sinking of the graben floor and a lateral extension of about 2 meters. Here we analyse Doppler measurements for the period January 1977 to November 1980. Point positions are computed for 7 to 10 day intervals using a precise ephemeris, and a moving window analysis is applied to the data. An apparent 2 meter uplift preceding the November 1978 seismic crisis is detected at Djibouti, whereas no similar phenomenon is observed at the two closest stations, Pretoria and Uccle-Brussels. However, field observations rule out a tectonic origin for this uplift. In Djibouti, the correlation between the apparent vertical station position and the electron density in the ionospheric F-layer reveals that a bias may be induced by the third order term of the ionospheric refractive index not previously taken into account, or more probably by the ray curvature through the ionosphere. This bias is particularly strong for our data set, from a station located close to the magnetic equator, and related to a period of rapid increase in the solar activity. Although our analysis fails to detect any tectonic displacement related to the rift seismic activity, it shows that similar tectonic studies by the Doppler method will be possible once the residual ionospheric errors are removed, for example by use of higher radio frequencies.     

卫星立体定位的仿真分析

本文从共线条件方程和前方交会的几何条件出发,推导了异轨和同轨模式下卫星立体定位的精度计算公式,仿真分析了轨道和姿态参数测量精度对卫星测绘能力的影响。实验结果表明,本文推导的精度计算公式正确合理。     

卫星定位技术在精准农业中的应用

卫星定位技术可以在精准农业的各个环节发挥作用，如精准播种、精准施肥、精准喷药、精准收割等等。卫星定位技术在农业机械中的应用，极大地提高了农业生产和作业效率。文章介绍了全球定位系(GPS)在精准农业作业流程中的应用，和美国Trimble公司生产的AgGPS农用卫星定位系统以及其在土壤采样中的应用实例。     

Doppler satellite observations of polar motion

Observations on Navy navigation satellites made by thirteen Doppler receiving stations have been used to determine the position of the earth's pole daily for a six month period of time. A precision of one meter has been obtained on the basis of forty-eight hours of observations on one satellite. No bias is apparant between computations based on different satellites, but differences of about a meter exist with respect to values published by the Bureau International de l'Heure on the basis of astronomical observations.     

基于道路的地球同步卫星定位松驰解法

针对文献中定位方法的弱点，提出了一种通过道路宽度进行强制约束的松驰解法。该方法不仅能提高高等级道路上用户的定位精度，而且在保证方差最小的情况下，使用户总被限制在道路上。     

卫星几何分布对GPS相对定位精度的影响

本文通过大量实例资料并从理论上进行分析论证卫星几何分布对GPS相对定位中基线精度的影响 ,在城市和矿区地面形变测量中 ,为了提高基线精度 ,提出了对GPS卫星几何分布有关的一些要求     

卫星导航定位系统时间同步技术

卫星导航定位系统测距的基础是测时,而定轨和定位的前提是各观测量的时间同步,因此,时间同步是卫星导航定位系统建设的关键。卫星导航定位系统中时间同步技术包括卫星与地面(星-地)和地面站间(地-地)的时间同步,主要时间同步方法有用于星-地时间同步的双向时间频率传递法(TWSTFT)、倒定位法等,以及用于地-地时间同步的TWSTFT、卫星共视法、搬运钟法等。本文重点介绍TWSTFT和卫星共视法进行时间同步的基本原理、精度分析和卫星导航定位系统的钟差预报。     

量子信道大气扰动延时补偿方法的研究

本文对量子卫星定位系统(QPS)中的纠缠光穿过大气电离层和对流层过程中所产生的路径延迟误差进行研究.根据电离层路径延迟与纠缠光频率以及纠缠光传播路径单位面积上电离层自由电子总含量(TEC)之间的关系,提出3种电离层路径延迟修正方案,并对每一种方案的优缺点进行分析.根据对流层路径延迟与气象参数之间的关系,以及气象参数与纬度、高度和年积日的关系,提出5种对流层路径延迟修正方案,并分析各修正方案的优缺点.本文所做研究有助于进一步提高QPS的精度.     

异源高分辨率光学卫星遥感影像联合定位

本文提出一种基于RFM和投影射线法的异源高分辨率光学卫星遥感影像定位算法:首先利用高分辨率遥感影像RFM正解模型迭代计算其反解模型;接着通过RFM正反解模型构建投影射线,最后采用迭代求取射线交点的方法确定地面三维实际坐标。实验对比结果表明,联合具有一定重叠度的异源高分辨率光学卫星遥感影像进行立体定位具有较强的可行性,并可达到一定的精度。     

Accurate absolute GPS positioning through satellite clock error estimation

 An algorithm for very accurate absolute positioning through Global Positioning System (GPS) satellite clock estimation has been developed. Using International GPS Service (IGS) precise orbits and measurements, GPS clock errors were estimated at 30-s intervals. Compared to values determined by the Jet Propulsion Laboratory, the agreement was at the level of about 0.1 ns (3 cm). The clock error estimates were then applied to an absolute positioning algorithm in both static and kinematic modes. For the static case, an IGS station was selected and the coordinates were estimated every 30 s. The estimated absolute position coordinates and the known values had a mean difference of up to 18 cm with standard deviation less than 2 cm. For the kinematic case, data obtained every second from a GPS buoy were tested and the result from the absolute positioning was compared to a differential GPS (DGPS) solution. The mean differences between the coordinates estimated by the two methods are less than 40 cm and the standard deviations are less than 25 cm. It was verified that this poorer standard deviation on 1-s position results is due to the clock error interpolation from 30-s estimates with Selective Availability (SA). After SA was turned off, higher-rate clock error estimates (such as 1 s) could be obtained by a simple interpolation with negligible corruption. Therefore, the proposed absolute positioning technique can be used to within a few centimeters' precision at any rate by estimating 30-s satellite clock errors and interpolating them. Received: 16 May 2000 / Accepted: 23 October 2000     

LEO satellite clock analysis and prediction for positioning applications

The positioning service aided by low Earth orbit (LEO) mega-constellations has become a hot topic in recent years. To achieve precise positioning, accuracy of t...     

Polar motion determined by Doppler satellite observations

Doppler observations of Navy Navigation Satellites have been used to comput pole positions on a daily basis since 1969. Limited computations have been performed using data on file for the period 1964–1969. Results of recent computations give a standard error in pole position based on 48 hours of Doppler observations of 7 cm. However, effects of errors in the orbit due to uncertainties in the gravity field prevent the attainment of this precision; the standard deviation of pole position for this time span is 60 cm, giving a standard error for a five day mean based on observations of two satellites of 25 cm.     

A set-membership approach for high integrity height-aided satellite positioning

A Robust Set-Inversion via Interval Analysis method in a bounded-error framework is used to compute three-dimensional location zones in real time, at a given confidence level. This approach differs significantly from the usual Gaussian error model paradigm, since the satellite positions and the pseudorange measurements are represented by intervals encompassing the true value with a particular level of confidence. The method computes a location zone recursively, using contractions and bisections of an arbitrarily large initial location box. Such an approach can also handle an arbitrary number of erroneous measurements using a q-relaxed solver and allows the integration of geographic and cartographic information such as digital elevation models or three-dimensional maps. With enough data redundancy, inconsistent measurements can be detected and even rejected. The integrity risk of the location zone comes only from the measurement bounds settings, since the solver is guaranteed. A method for setting these bounds for a particular location zone confidence level is proposed. An experimental validation using real L1 code measurements and a digital elevation model is also reported in order to illustrate the performance of the method on real data.     

“卫星导航定位”课程实践教学创新体系改革

"卫星导航定位"课程是我校测绘类专业本科生的一门具有较强理论性和实践性的专业基础课,为强化学生知识运用能力、测绘实践操作能力、程序设计能力及科技创新能力,从实践教学内容更新及实践教学方法和手段优化等方面对该课程的实践教学创新体系(课间实验和集中实习)探索性改革,经两年的教学实践与持续改进,实际效果显著。     

一种大倾角敏捷成像卫星影像的直接定位方法

发展光学敏捷成像卫星的应用是国际上高分辨率对地观测领域的主要趋势,卫星在轨机动能力的增强使大倾角成像条件下的无控定位问题成为热点。为了获取影像对应的准确物方坐标,该文结合大倾角光学敏捷卫星的成像特点,对卫星俯视、侧视成像以及地面分辨率变化等系统误差源及其变化规律进行定量化推导分析,并在此基础上提出了适合短时间成像的轨道运动模型和参数估计方法,建立了顾及大倾角成像特点的严格几何定位模型,提供了影像无控制点直接定位的处理流程。实验结果证明所提出的方法能够较好地校正大倾角成像的几何偏差,使严密无控定位精度控制在1个像素内的水平。     

GDCORS多星系统定位平台测试与分析

广东省连续运行卫星定位服务系统(G DCORS)建成了兼容多星系统的北斗地基增强平台,组织开展了新平台与原平台的外业测试.并从内符合精度评定、重复性精度评定、外符合精度、初始化时长等方面对网络实时动态(RTK)定位结果进行了统计和比对分析.测试结果表明,新平台能够提供高可靠性、高精度的网络RTK服务.文中研究结果可为GDCORS用户使用新/原平台提供实际应用参考.     

优化部分有理多项式系数的卫星影像精确定位

针对目前在补偿卫星影像RPC模型对地定位的系统误差时所广泛采用的像方补偿方法存在需要引入附加参数、无法从实质上消除RPC参数中系统误差的不足,该文提出了一种利用少量地面控制点直接对部分RPC参数进行优化来补偿定位的系统误差的方法,并将该方法进一步运用到基于RPC模型的区域网平差中。以武汉地区和法国Sainte-Maxime地区的ZY-3卫星影像为实验对象,在空间前方交会和区域网平差实验中将本文方法与像方补偿方法做了充分对比。实验结果表明,该方法可达到不低于像方补偿方法的理想定位精度。同时,与像方补偿方法相比,该方法不需引入附加补偿参数,优化后RPC模型形式统一,更加便于后续的计算和处理,可以实现真正意义上的基于RPC模型的卫星遥感影像精确定位。     

混合星座的精度因子与定位性能分析

通过对静地同步卫星(GEO)、倾斜轨道同步卫星(IGSO)/GEO结合和MEO/GEO结合等星座的精度因子(DOP)计算和分析,初步探索了利用混合星座解决无高程辅助的纯GEO星座不能垂向定位和水平定位精度欠佳的问题。同时,结合我国卫星导航系统的发展,提出利用IGSO/GEO混合星座作为区域定位星座向全球定位星座过渡的观点。