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1.
本文在仿真出GPS系统与BDS系统卫星星座的基础上,对两种定位系统下的哈尔滨、武汉、广州、拉萨单个站点以及全球范围的卫星可见性、DOP值、定位精度进行了覆盖分析,并比较了两个系统定位性能的差异。实验结果表明,当前BDS系统在亚太地区与GPS系统的定位性能基本一致,可见卫星数比GPS系统稍多,但BDS系统的DOP值的波动却比GPS系统的要大,尤其在GEO与IGSO卫星覆盖的边缘区域,BDS的导航定位性能较差,在某些地区仍不能提供导航定位服务。 相似文献
2.
由于天线本身的特性及机械加工等原因,GPS卫星和接收机天线相位中心与其几何中心不重合,从而产生相位中心偏差。某些类型的天线该偏差甚至可达数cm,直接影响高精度GPS测量的精确可靠性[1]。讨论了GAMIT软件在高精度GPS数据处理中进行天线相位中心改正的原理、方法和策略,结合美国IGS观测站及南加州区域站观测数据,对改正方法及策略进行了实验对比与分析。结果表明:对接收机天线相位中心和卫星天线相位中心采用模型改正,而卫星天线相位中心偏移不改正,所得到的基线解算结果较好[2];地面接收机天线方位角的变化对U方向的基线解算结果有较大影响,在高精度GPS测量中,必须进行天线方位角的变化改正。 相似文献
3.
多系统GNSS卫星组合定位成为导航系统发展的重要趋势。基于武汉大学IGS数据中心发布的精密星历,以可见卫星数及PDOP为研究对象,通过地面点仿真实验,分析多系统GNSS卫星在全球范围内可见性的时空变化,比较多系统GNSS相较单系统在卫星分布上的优势。结果表明,对于地面固定点,各GNSS系统卫星可见性的重复周期都约为24h,其中GPS/BDS/GLONASS/Galileo 4系统的卫星可见性稳定性最高,单GPS系统较差;相较于GPS单系统,GPS/BDS双系统在亚太地区的可见卫星数由7~13颗提高到15~23颗,而GPS/BDS/GLONASS/Galileo 4系统在欧亚和亚太地区的可见卫星数提高到24~30颗。 相似文献
4.
由于天线本身的特性及机械加工等原因,GPS卫星和接收机天线相位中心与其几何中心不重合,从而产生相位中心偏差。某些类型的天线该偏差甚至可达数cm,直接影响高精度GPS测量的精确可靠性。IGS改正模型文件中给出的是每隔5°方位角和天顶角时的天线相位中心变化改正值,本文用VS程序设计通过线性内插算法获得任意方位角和天顶角下的相位中心变化改正值。 相似文献
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基于我们的车载 DGPS试验成果和 DDKIN动态载波相位测量数据处理软件,本文主要论述了 GPS 动态定位的下列技术问题:依据 GPS卫星给用户提供的 User Range Accuracy值,选择定位星座;顾及运动载体的特点,选用 GPS信号接收天线及其在载体上的安设位置;用 Trimvec Plus和DDKIN 软件,精细处理一秒数据率的动态载波相位测量数据。 相似文献
8.
针对BDS-3正式卫星对BDS-2和GPS系统定位精度的影响,以IGS连续跟踪站实测数据为基础,分别设计了加入BDS-3新卫星对BDS-2 B1 I频率和GPS系统L5频率标准单点定位精度的影响实验.实验结果表明,BDS-3新卫星的加入能有效提升BDS-2和GPS卫星可见数,降低BDS-2和GPS PDOP值,同时也有... 相似文献
9.
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
10.
基于STK的全球卫星导航定位系统DOP值仿真 总被引：1，自引：0，他引：1
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。 相似文献
11.
Phase center modeling for LEO GPS receiver antennas and its impact on precise orbit determination 总被引：7，自引：5，他引：7
Adrian Jäggi R. Dach O. Montenbruck U. Hugentobler H. Bock G. Beutler 《Journal of Geodesy》2009,83(12):1145-1162
Most satellites in a low-Earth orbit (LEO) with demanding requirements on precise orbit determination (POD) are equipped with
on-board receivers to collect the observations from Global Navigation Satellite systems (GNSS), such as the Global Positioning
System (GPS). Limiting factors for LEO POD are nowadays mainly encountered with the modeling of the carrier phase observations,
where a precise knowledge of the phase center location of the GNSS antennas is a prerequisite for high-precision orbit analyses.
Since 5 November 2006 (GPS week 1400), absolute instead of relative values for the phase center location of GNSS receiver
and transmitter antennas are adopted in the processing standards of the International GNSS Service (IGS). The absolute phase
center modeling is based on robot calibrations for a number of terrestrial receiver antennas, whereas compatible antenna models
were subsequently derived for the remaining terrestrial receiver antennas by conversion (from relative corrections), and for
the GNSS transmitter antennas by estimation. However, consistent receiver antenna models for space missions such as GRACE
and TerraSAR-X, which are equipped with non-geodetic receiver antennas, are only available since a short time from robot calibrations.
We use GPS data of the aforementioned LEOs of the year 2007 together with the absolute antenna modeling to assess the presently
achieved accuracy from state-of-the-art reduced-dynamic LEO POD strategies for absolute and relative navigation. Near-field
multipath and cross-talk with active GPS occultation antennas turn out to be important and significant sources for systematic
carrier phase measurement errors that are encountered in the actual spacecraft environments. We assess different methodologies
for the in-flight determination of empirical phase pattern corrections for LEO receiver antennas and discuss their impact
on POD. By means of independent K-band measurements, we show that zero-difference GRACE orbits can be significantly improved
from about 10 to 6 mm K-band standard deviation when taking empirical phase corrections into account, and assess the impact
of the corrections on precise baseline estimates and further applications such as gravity field recovery from kinematic LEO
positions. 相似文献
12.
GPS code pseudorange measurements exhibit group delay variations at the transmitting and the receiving antenna. We calibrated C1 and P2 delay variations with respect to dual-frequency carrier phase observations and obtained nadir-dependent corrections for 32 satellites of the GPS constellation in early 2015 as well as elevation-dependent corrections for 13 receiving antenna models. The combined delay variations reach up to 1.0 m (3.3 ns) in the ionosphere-free linear combination for specific pairs of satellite and receiving antennas. Applying these corrections to the code measurements improves code/carrier single-frequency precise point positioning, ambiguity fixing based on the Melbourne–Wübbena linear combination, and determination of ionospheric total electron content. It also affects fractional cycle biases and differential code biases. 相似文献
13.
Cheinway Hwang Tzu-Pang Tseng Ting-Jung Lin Dražen Švehla Urs Hugentobler Benjamin Fong Chao 《GPS Solutions》2010,14(1):121-131
The precise orbit determination antennas of F3/C and GRACE-A satellites are from the same manufacturer, but are installed
in different configurations. The current orbit accuracy of F3/C is 3 cm at arcs with good GPS data, compared to 1 cm of GRACE,
which has a larger ratio of usable GPS data. This paper compares the qualities of GPS observables from F3/C and GRACE. Using
selected satellites and time spans, the following average values for the satellite F3/C and satellite A of GRACE are obtained:
multipath effect on the pseudorange P1, 0.78 and 0.38 m; multipath effect on the pseudorange P2, 1.03 and 0.69 m; occurrence
frequency of cycle slip, 1/29 and 1/84; standard error of unit weight, 4 and 1 cm; dynamic–kinematic orbit difference, 10
and 2 cm. For gravity determination using F3/C GPS data, a careful selection of GPS data is critical. With six satellites
in orbit, F3/C’s large amount of GPS data will make up the deficiency in data quality. 相似文献
14.
This study analyzes the quality of onboard data of tracking signals from GPS satellites on the far side of the earth and determines the orbit of the geostationary satellite using code and carrier phase observations with 30-h and 3-day orbit arc length. According to the analysis results, the onboard receiver can track 6–8 GPS satellites, and the minimum and maximum carrier to noise spectral densities were 24 and 45 dB-Hz, respectively. For a GPS receiver on a high-altitude platform above the navigation constellations, the blocking of the earth and a weak signal strength usually cause a piece-wise GPS signal tracking and an increase in the number of ambiguity parameters. Individual GPS satellites may be continuously tracked for as little as several minutes and as long as 3 h. Moreover, considering the negative sign of elevation angles reflects the fact that GPS satellites are tracked below the receiver in the study. GPS satellites appear mainly in the elevation angle range of ??53° to ??83°, and dilution of precision values could reach ten or one hundred and more. Also, it is observed that when a signal suffers from atmospheric refraction, other GPS signals tracked simultaneously by the receiver experience strong systematic errors in the code observations. Based on single-frequency code and carrier phase measurements, the mean 3D root mean square (RMS) value of the overlap comparisons between 30-h orbit determination arcs is 2.14 m. However, we found that there were also some biases in the carrier phase residuals, which contributed to poor orbit accuracy. To eliminate the effects of the biases, we established a correction sequence for each GPS satellite. After corrections, the mean 3D RMS was reduced to 0.99 m, representing a 53% improvement. 相似文献
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16.
Wavelet packets based denoising method for measurement domain repeat-time multipath filtering in GPS static high-precision positioning 总被引：1，自引：1，他引：0
Lawrence Lau 《GPS Solutions》2017,21(2):461-474
Repeatable satellite orbits can be used for multipath mitigation in GPS-based deformation monitoring and other high-precision GPS applications that involve continuous observation with static antennas. Multipath signals at a static station repeat when the GPS constellation repeats given the same site environment. Repeat-time multipath filtering techniques need noise reduction methods to remove the white noise in carrier phase measurement residuals in order to retrieve the carrier phase multipath corrections for the next day. We propose a generic and robust three-level wavelet packets based denoising method for repeat-time-based carrier phase multipath filtering in relative positioning; the method does not need tuning to work with different data sets. The proposed denoising method is tested rigorously and compared with two other denoising methods. Three rooftop data sets collected at the University of Nottingham Ningbo China and two data sets collected at three Southern California Integrated GPS Network high-rate stations are used in the performance assessment. Test results of the wavelet packets denoising method are compared with the results of the resistor–capacitor (RC) low-pass filter and the single-level discrete wavelet transform (DWT) denoising method. Multipath mitigation efficiency in carrier phase measurement domain is shown by spectrum analysis of two selected satellites in two data sets. The positioning performance of the repeat-time-based multipath filtering techniques is assessed. The results show that the performance of the three noise reduction techniques is about 1–46 % improvement on positioning accuracy when compared with no multipath filtering. The statistical results show that the wavelet packets based denoising method is always better than the RC filter by 2–4 %, and better than the DWT method by 6–15 %. These results suggest that the proposed wavelet packets based denoising method is better than both the DWT method and the relatively simple RC low-pass filter for noise reduction in multipath filtering. However, the wavelet packets based denoising method is not significantly better than the RC filter. 相似文献
17.
Precision real-time navigation of LEO satellites using global positioning system measurements 总被引：4，自引：3，他引：1
Continued advancements in remote sensing technology along with a trend towards highly autonomous spacecraft provide a strong
motivation for accurate real-time navigation of satellites in low Earth orbit (LEO). Global Navigation Satellite System (GNSS)
sensors nowadays enable a continuous tracking and provide low-noise radiometric measurements onboard a user spacecraft. Following
the deactivation of Selective Availability a representative real-time positioning accuracy of 10 m is presently achieved by
spaceborne global positioning system (GPS) receivers on LEO satellites. This accuracy can notably be improved by use of dynamic
orbit determination techniques. Besides a filtering of measurement noise and other short-term errors, these techniques enable
the processing of ambiguous measurements such as carrier phase or code-carrier combinations. In this paper a reference algorithm
for real-time onboard orbit determination is described and tested with GPS measurements from various ongoing space missions
covering an altitude range of 400–800 km. A trade-off between modeling effort and achievable accuracy is performed, which
takes into account the limitations of available onboard processors and the restricted upload capabilities. Furthermore, the
benefits of different measurements types and the available real-time ephemeris products are assessed. Using GPS broadcast
ephemerides a real-time position accuracy of about 0.5 m (3D rms) is feasible with dual-frequency carrier phase measurements.
Slightly inferior results (0.6–1 m) are achieved with single-frequency code-carrier combinations or dual-frequency code. For
further performance improvements the use of more accurate real-time GPS ephemeris products is mandatory. By way of example,
it is shown that the TDRSS Augmentation Service for Satellites (TASS) offers the potential for 0.1–0.2 m real-time navigation
accuracies onboard LEO satellites. 相似文献
18.
在精密单点定位中,相位缠绕是一项不可忽略的误差。相位缠绕的计算严格依赖于卫星姿态的确立,不同的卫星类型产生不同的异常。本文给出了卫星在正常情况下的姿态模型和在异常情况下的姿态改正模型。使用真实数据测试以验证本文所提出模型的正确性。观察滤波收敛后出现异常情况的卫星观测值的残差,结果表明:在异常时期残差最大可能超过20 cm,然而使用本文的改正模型,残差可降低到5 cm以下。使用不同分析中心的精密轨道和钟差产品,效果存在微小差异。II/IIA卫星通过地影区域的时间最长可达1 h,此期间卫星姿态完全受航向角偏差(II/IIA为+0.5°)控制,出了地影区域后30 min,姿态难以模型化,因此这30 min的观测数据不建议采用。 相似文献
19.
Coherent GPS reflections from the sea surface 总被引：1，自引：0，他引：1
In this letter, we explore a method to obtain accurate ocean heights using measurements of the global positioning system (GPS) carrier phase after reflection on the sea surface. A carrier tracking algorithm is employed in measuring travel path differences between GPS direct and reflected signals collected from antennas suspended over a marine estuary, when roughness guarantees partially coherent reflections at the GPS L1 frequency. This technique proves to be sensitive to surface roughness and able to follow tide variations with a precision better than 5 cm (1-sigma) for sea states with significant wave heights below 10 cm. It is expected that this technique could be further extended to rougher sea states using GPS frequency combinations with longer synthetic wavelengths. 相似文献
20.
全球定位系统(global positioning system,GPS)卫星的IIR和IIF卫星能够在各个信号分量之间重新分配其发送信号的功率,一个或多个GPS信号可以在指定区域根据需要进行功率调整或者关闭。分析GPS信号的变化特征对于地面和空间应用有重要的意义。风云三号D（FengYun-3D,FY-3D）卫星是中国极轨气象卫星之一,利用FY-3D卫星实际测量数据可以帮助GPS用户全面了解GPS功率调整的特点。首先,利用FY-3D运行轨道全球覆盖的特点分析GPS信号的强度,特别是GPS信号功率调整时间段信号变化的特点;然后,使用在轨数据研究了全球范围L波段信号干扰的特征,得到了干扰对全球导航卫星系统掩星探测仪掩星天线的自动增益控制和基底噪声的影响。结果表明:从2020-02-14开始的GPS功率调整以[35°N,37°E]和[35°N,69°E]为中心,覆盖半径约为7 500 km,在该区域内GPS P(Y)码功率增加约10 dB;GPS L1和L2频段在中东地区持续受干扰的影响,该区域的基底噪声比其他区域增加约3~10倍;干扰区域中心点和GPS功率调整区域中心点大致在同一位置。GPS卫星的功率调整和信号干扰对GPS用户,特别是低轨卫星的定位有明显的影响,在GNSS接收机设计时应引起重视。 相似文献