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1.
LEO星座参数对GPS掩星数量和时空分布影响的模拟研究 总被引：3，自引：0，他引：3
利用低地球轨道LEO(Low Earth Orbit)卫星上的星载接收机对GPS卫星进行掩星观测反演地球的大气性质,对于气象学和大气研究具有重要意义.与单颗LEO卫星相比,由多个卫星组成的LEO星座观测到的掩星事件在时空分辨率和数量上都有很大的提高.考虑特定的区域,采用数值模拟方法,对不同卫星数和不同星座参数k的玫瑰型星座在一天内所观测的掩星事件的数量和分布进行比较分析,得到相应结论.研究成果对实际发射LEO星座时相关参数的选取具有参考价值. 相似文献
2.
Improved antenna phase center models for GLONASS 总被引：6，自引：2，他引：4
Rolf Dach Ralf Schmid Martin Schmitz Daniela Thaller Stefan Schaer Simon Lutz Peter Steigenberger Gerhard Wübbena Gerhard Beutler 《GPS Solutions》2011,15(1):49-65
Thanks to the increasing number of active GLONASS satellites and the increasing number of multi-GNSS tracking stations in
the network of the International GNSS Service (IGS), the quality of the GLONASS orbits has become significantly better over
the last few years. By the end of 2008, the orbit RMS error had reached a level of 3–4 cm. Nevertheless, the strategy to process
GLONASS observations still has deficiencies: one simplification, as applied within the IGS today, is the use of phase center
models for receiver antennas for the GLONASS observations, which were derived from GPS measurements only, by ignoring the
different frequency range. Geo++ GmbH calibrates GNSS receiver antennas using a robot in the field. This procedure yields
now separate corrections for the receiver antenna phase centers for each navigation satellite system, provided its constellation
is sufficiently populated. With a limited set of GLONASS calibrations, it is possible to assess the impact of GNSS-specific
receiver antenna corrections that are ignored within the IGS so far. The antenna phase center model for the GLONASS satellites
was derived in early 2006, when the multi-GNSS tracking network of the IGS was much sparser than it is today. Furthermore,
many satellites of the constellation at that time have in the meantime been replaced by the latest generation of GLONASS-M
satellites. For that reason, this paper also provides an update and extension of the presently used correction tables for
the GLONASS satellite antenna phase centers for the current constellation of GLONASS satellites. The updated GLONASS antenna
phase center model helps to improve the orbit quality. 相似文献
3.
4.
This study makes an initial comparison of three GPS-like constellations. Starting with a simplified constellation of 25 GPS satellites as a reference, GPS(25), we determine what kinematic positioning improvements would result from a constellation comprising a Hi component of 16 GPS satellites (at roughly 16.8 earth radii) coupled with a Lo component of 49 GPS satellites (at roughly 2.1 earth radii). We also include a GPS constellation of 49 GPS satellites, GPS(49), which comprises orbits like the GPS(25) constellation. The GPS(49) and the Hi(16)/Lo(49) constellations have semi-major axes selected so that they have exactly the same average number of satellites above 7.5 degrees elevation (averaged over 24 hours). What motivated this study was a need to measure the benefits, to precision differential kinematic positioning methods (i.e., RTK), which result from the higher Doppler shifts (hence speedier integrated Doppler) generated by the Lo component. Quicker initial convergence was anticipated, of course. 相似文献
5.
Dennis Odijk Nandakumaran Nadarajah Safoora Zaminpardaz Peter J. G. Teunissen 《GPS Solutions》2017,21(2):439-450
Knowledge of inter-system biases (ISBs) is essential to combine observations of multiple global and regional navigation satellite systems (GNSS/RNSS) in an optimal way. Earlier studies based on GPS, Galileo, BDS and QZSS have demonstrated that the performance of multi-GNSS real-time kinematic positioning is improved when the differential ISBs (DISBs) corresponding to signals of different constellations but transmitted at identical frequencies can be calibrated, such that only one common pivot satellite is sufficient for inter-system ambiguity resolution at that particular frequency. Recently, many new GNSS satellites have been launched. At the beginning of 2016, there were 12 Galileo IOV/FOC satellites and 12 GPS Block IIF satellites in orbit, while the Indian Regional Navigation Satellite System (IRNSS) had five satellites launched of which four are operational. More launches are scheduled for the coming years. As a continuation of the earlier studies, we analyze the magnitude and stability of the DISBs corresponding to these new satellites. For IRNSS this article presents for the first time DISBs with respect to the L5/E5a signals of GPS, Galileo and QZSS for a mixed-receiver baseline. It is furthermore demonstrated that single-frequency (L5/E5a) ambiguity resolution is tremendously improved when the multi-GNSS observations are all differenced with respect to a common pivot satellite, compared to classical differencing for which a pivot satellite is selected for each constellation. 相似文献
6.
7.
针对低轨卫星快速空间几何变化和抗干扰能力强等特征,该文基于卫星工具包软件对全球导航定位系统和铱星系统星座进行了仿真,并假定铱星具有导航卫星的功能,分析铱星对GPS定位的增强作用。首先对GPS和铱星增强星座的可见卫星数量和几何精度因子值进行了分析,然后通过对不同的误差值建模,对GPS系统和铱星系统的观测值进行了仿真,分析了低轨卫星对双差定位浮点解和模糊度固定的增强作用,结果表明:低轨卫星的加入增加了可见卫星数量,几何精度因子也优于单GPS系统。单频双差模糊度浮点解的RMS值优于1周,双频双差模糊度浮点解的RMS值优于0.5周,与单GPS相比有了较明显的提高,同时,低轨卫星的加入更有利于单频短基线的模糊度固定。 相似文献
8.
针对低轨卫星星座有待合理化设计的问题,深入研究了低轨卫星星座增强北斗三号系统定位性能。分析轨道高度、轨道倾角、星座构型对星座覆盖性能的影响,仿真北斗三号、GPS和3种不同类型的低轨星座,研究各低轨星座与北斗三号、GPS的组合系统在所选7个测站以及全球范围内的可见卫星数和PDOP值分布。结果表明低轨卫星对北斗三号的增强效果主要与低轨卫星数目有关,且不同轨道倾角的组合低轨星座有利于均衡系统在全球范围内的可见卫星数与PDOP值分布。低轨卫星有望通过改善卫星观测几何构型提高北斗三号系统的定位性能,且增强效果与低轨星座构型密切相关。 相似文献
9.
The site-specific multipath characteristics of 217 Global Positioning System (GPS) sites worldwide were analyzed using the variability of the post-fit phase residuals. Because the GPS satellite constellation returns to the same configuration in a sidereal day (23 h 56 min 4 s), the multipath repeats on that period. However, daily GPS position estimates are usually based on the solar day. When several days of GPS data are processed, this steady change in the orientation of the satellite constellation with respect to the station manifests itself in the form of patterns in the post-fit phase residuals which shift by 3 min 56 s per day. It was found that the mean root mean square of the time-shifted post-fit phase residuals is highly dependent on the GPS antenna type. The conclusions derived from the analysis of the time-shifted post-fit residuals were verified by performing a cross-correlation of the post-fit residuals across many days for selected sites. 相似文献
10.
Single receiver phase ambiguity resolution with GPS data 总被引：26，自引：12，他引：14
Willy Bertiger Shailen D. Desai Bruce Haines Nate Harvey Angelyn W. Moore Susan Owen Jan P. Weiss 《Journal of Geodesy》2010,84(5):327-337
Global positioning system (GPS) data processing algorithms typically improve positioning solution accuracy by fixing double-differenced
phase bias ambiguities to integer values. These “double-difference ambiguity resolution” methods usually invoke linear combinations
of GPS carrier phase bias estimates from pairs of transmitters and pairs of receivers, and traditionally require simultaneous
measurements from at least two receivers. However, many GPS users point position a single local receiver, based on publicly
available solutions for GPS orbits and clocks. These users cannot form double differences. We present an ambiguity resolution
algorithm that improves solution accuracy for single receiver point-positioning users. The algorithm processes dual- frequency
GPS data from a single receiver together with wide-lane and phase bias estimates from the global network of GPS receivers
that were used to generate the orbit and clock solutions for the GPS satellites. We constrain (rather than fix) linear combinations
of local phase biases to improve compatibility with global phase bias estimates. For this precise point positioning, no other
receiver data are required. When tested, our algorithm significantly improved repeatability of daily estimates of ground receiver
positions, most notably in the east component by approximately 30% with respect to the nominal case wherein the carrier biases
are estimated as real values. In this “static” test for terrestrial receiver positions, we achieved daily repeatability of
1.9, 2.1 and 6.0 mm in the east, north and vertical (ENV) components, respectively. For kinematic solutions, ENV repeatability
is 7.7, 8.4, and 11.7 mm, respectively, representing improvements of 22, 8, and 14% with respect to the nominal. Results from
precise orbit determination of the twin GRACE satellites demonstrated that the inter-satellite baseline accuracy improved
by a factor of three, from 6 to 2 mm up to a long-term bias. Jason-2/Ocean Surface Topography Mission precise orbit determination
tests results implied radial orbit accuracy significantly below the 10 mm level. Stability of time transfer, in low-Earth
orbit, improved from 40 to 7 ps. We produced these results by applying this algorithm within the Jet Propulsion Laboratory’s
(JPL’s) GIPSY/OASIS software package and using JPL’s orbit and clock products for the GPS constellation. These products now
include a record of the wide-lane and phase bias estimates from the underlying global network of GPS stations. This implies
that all GIPSY–OASIS positioning users can now benefit from this capability to perform single-receiver ambiguity resolution. 相似文献
11.
首先描述卫星覆盖的理论以及卫星星下点在地面上的轨迹规律,然后根据导航星座的特点,通过对星座基本参数特点的讨论,并在参考GPS和GLONASS星座的基础上,确定了导航星座的构成。最后,在理论上证明了最小覆盖性的条件,随着模拟实际数据进行了验证。 相似文献
12.
在卫星定位中,观测环境的优劣对最终定位结果精度有着显著性影响,单GPS系统因为其可观测卫星颗数少和自身星座分布的共同影响,载波相位周跳频繁,定位解的误差大、可靠性低、稳定性差。本文对多模GNSS （ Global Navigation Satellite System ）解算中时空系统的统一,组合单点定位模型和差分定位模型等关键技术进行了研究,实现了多模GNSS组合定位,改善了卫星相对于测站的几何分布,环境适应性加强,使得定位精度、系统冗余度和可靠性大幅提高,最后使用车载数据进行实验验证。验证结果表明,多模GNSS观测卫星数相比单GPS系统而言,观测卫星数增加了2倍,PDOP值降低了42％,极大地提高了差分定位解的成功率,固定解比例提高了18．3％。这充分说明了多模GNSS统一定位的可行性和优越性。 相似文献
13.
随着北斗卫星导航系统的逐渐完善,有关北斗系统定位的研究越来越深入,为了对比分析北斗系统和全球定位导航系统(GPS)定位的差异性,充分利用北斗地球静止轨道卫星(GEO)和倾斜地球同步轨道卫星(IGSO)高轨道卫星的特殊性,本文提出一种新的组合选星方法,选取卫星数较少且Position Dilution of Precision(PDOP)最小的北斗/GPS组合,分别对比分析北斗系统、GPS系统及其组合系统在楼顶开放环境和楼间恶劣环境下的定位效果。实验结果表明:北斗比GPS有更加稳定的定位效果,依据本文组合选星方法,利用少量卫星即可获得较好的定位精度。 相似文献
14.
在卫星连续动态定位和超短基线快速静态定位中，当测站和卫星处于特殊位置时，卫星星座会产生危险图形问题，卫星星座的图形强度的精度因子DOP在极短的观测时间内显著地变化，从而导致法方程系数阵奇异，测站坐标产生不定解。本文分析了产生危险图形的原因以及它对定位结果的影响。 相似文献
15.
差分码偏差(differential code bias,DCB)是指由全球导航卫星系统(global navigation satellite system, GNSS)信号接收和发射硬件导致的频率相关的偏差项,对电离层估计有显著的影响,在利用GNSS观测数据提取电离层总电子含量时需要被精确修正,研究利用低轨卫星的星载GNSS观测数据估计DCB尤为重要。使用Swarm星座3颗卫星GPS接收机2016年1月的双频观测值,设计了独立估计和联合估计两种估计方案,采用附加限制条件的间接平差方法对GPS卫星以及星载接收机的DCB进行估计。以中国科学院和德国宇航中心的DCB产品作为参考,分析了两种估计方案的精度和稳定性,相较于独立估计方案,联合估计方案得到的GPS卫星DCB的稳定性较独立估计方案提高了16.6%,且与参考DCB具有更好的一致性。 相似文献
16.
针对采用单卫星定位系统时,在城市高楼密集区和位于深山峡谷的水库、电站、矿山等环境下,GNSS用户接收到的卫星个数少且卫星分布不佳导致的可用性下降、定位精度较差的问题,提出多系统组合的定位方法。利用GPS、GLONASS及GALILE0系统的轨道参数模拟卫星星座,计算不同卫星高度角下单系统及组合系统的DOP值,根据DOP值分析其可用性。研究表明：在全球时空范围内、相同卫星高度角下,组合系统的可用性高于单系统,三系统组合的可用性高于双系统组合。 相似文献
17.
与全球定位系统（global positioning system,GPS）不同,北斗区域卫星导航系统（BeiDou navigation satellite system,BDS）采用了5颗地球静止轨道卫星、5颗倾斜地球同步轨道卫星和4颗中圆轨道卫星的混合星座,星座分布不均匀。特殊星座决定了不同纬度地区用户的可见卫星数量和观测几何结构存在明显差异,用户的导航定位性能存在明显的纬度效应。分别从理论模型和实际观测两个方面对不同纬度地区用户的可见卫星数目、观测几何结构和导航定位性能进行较全面分析,使用了多家厂商的接收机,在不同纬度地区进行了GPS、BDS以及两系统融合定位试验。结果表明,BDS定位性能存在明显的纬度效应,即定位精度随纬度升高而降低;GPS导航定位性能没有明显的纬度效应;BDS/GPS数据融合可以减弱纬度效应,提高导航定位服务的精度和可靠性。 相似文献
18.
Characterization of periodic variations in the GPS satellite clocks 总被引：11，自引：7，他引：4
The clock products of the International Global Navigation Satellite Systems (GNSS) Service (IGS) are used to characterize
the timing performance of the GPS satellites. Using 5-min and 30-s observational samples and focusing only on the sub-daily
regime, approximate power-law stochastic processes are found. The Block IIA Rb and Cs clocks obey predominantly random walk
phase (or white frequency) noise processes. The Rb clocks are up to nearly an order of magnitude more stable and show a flicker
phase noise component over intervals shorter than about 100 s. Due to the onboard Time Keeping System in the newer Block IIR
and IIR-M satellites, their Rb clocks behave in a more complex way: as an apparent random walk phase process up to about 100 s
and then changing to flicker phase up to a few thousand seconds. Superposed on this random background, periodic signals have
been detected in all clock types at four harmonic frequencies, n × (2.0029 ± 0.0005) cycles per day (24 h coordinated universal time or UTC), for n = 1, 2, 3, and 4. The equivalent fundamental period is 11.9826 ± 0.0030 h, which surprisingly differs from the reported mean
GPS orbital period of 11.9659 ± 0.0007 h by 60 ± 11 s. We cannot account for this apparent discrepancy but note that a clear
relationship between the periodic signals and the orbital dynamics is evidenced for some satellites by modulations of the
spectral amplitudes with eclipse season. All four harmonics are much smaller for the IIR and IIR-M satellites than for the
older blocks. Awareness of the periodic variations can be used to improve the clock modeling, including for interpolation
of tabulated IGS products for higher-rate GPS positioning and for predictions in real-time applications. This is especially
true for high-accuracy uses, but could also benefit the standard GPS operational products. The observed stochastic properties
of each satellite clock type are used to estimate the growth of interpolation and prediction errors with time interval. 相似文献
19.
采用双系统组合定位模式,导航接收机能在同一时刻接收到超过20颗可见星,大大增加了可见星的数量,能提供十分精准的定位。但可见星数量大幅度增加带来定位精度提升的同时也带来了大量的计算量,加上实际作业中的一些问题,都大大增加了选星时间。本文从GDOP与星座几何布局的关系出发,结合实际应用场景,提出了基于仰角和方位角排序的选星算法。该方法以满足定位要求为前提,根据可见星仰角排序初筛卫星,对不同仰角卫星进行合理的顶星选择,以卫星均匀分布为原则,将在理想情况和实际情况下寻找有效定位平衡点,以规避无效选星并减少计算量,从而大大减少选星时间,有效实现了在北斗和GPS双模定位中的快速选星。 相似文献
20.
现阶段高轨道航天器导航主要依靠地基测控系统,为了研究全球卫星导航系统(GNSS)技术用于高轨道航天器导航的可行性,对GNSS技术在地球静止轨道(GEO)卫星、倾斜地球同步轨道(IGSO)卫星航天器中的导航精度及适用性展开了分析研究. 采用2021年11月9日的两行轨道数据(TLE)仿真GNSS星座,以不同星下点的GEO卫星和不同倾角的IGSO卫星作为目标星展开导航仿真试验. 实验结果表明:为了满足GNSS解算所需的卫星数量,须通过接收旁瓣信号来增加可见卫星数目. 对GEO目标星而言,当接收机灵敏度高于?169 dB时,导航精度可达30 m;利用GPS对7个不同的GEO或IGSO轨道目标星进行导航实验表明,GPS对目标星导航的位置误差约为35 m;北斗三号(BDS-3)、GPS、GLONASS、Galileo的导航位置误差均值分别为28.03 m、21.16 m、37.15 m、25.09 m,具有良好的内符合精度,其中GPS精度最高,GLONASS精度最低,但大部分时段也在45 m内. 相似文献