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本文分析了GPS现代化信号L5载波的结构及相对于非现代化信号的改进,比较了GPS L5载波和WAAS L5载波的区别;比较了2颗现代化卫星SVN49和SVN62播发的L5载波的信号结构及信噪比,结果表明:SVN49播发的L5载波演示信号的抗干扰能力较差,而SVN62播发的L5载波具有更强的抗干扰能力,满足设计规范要求。 相似文献
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机载GPS反射信号土壤湿度测量技术 总被引:8,自引:2,他引:8
随着全球导航定位系统反射信号(GNSS-R)技术的发展, 近年来提出了利用GPS地表反射信号遥感土壤湿度的新方法, 该方法利用地表反射率与土壤介电常数以及介电常数与土壤湿度之间的关系来建立反演模型。为了可以快速方便的利用DMR实测数据反演得到土壤湿度, 本文根据Wang和Schmugge模型建立了土壤介电常数与湿度之间的分段模型, 实现了从原始反射数据到土壤湿度结果的整个反演流程。为了验证反演的可行性, 利用NASA等机构联合进行的SMEX02试验机载数据反演得到的结果表明, GPS反射信号能够有效地反演 相似文献
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Annual deformation signals from homogeneously reprocessed VLBI and GPS height time series 总被引:3,自引:3,他引:0
Volker Tesmer Peter Steigenberger Markus Rothacher Johannes Boehm Barbara Meisel 《Journal of Geodesy》2009,83(10):973-988
The first part of this paper compares homogeneously reprocessed Very Long Baseline Interferometry (VLBI) and Global Positioning
System (GPS) long-term height series from 1994 to 2007. The data analysis used fully adapted state-of-the-art models (like
VMF1 and a priori zenith delays from ECMWF) for the GPS and VLBI processing. The series are compared in terms of long-term
non-linear behaviour, harmonic and mean annual signals (not necessarily of harmonic nature). The similarity between both techniques
is very good (especially the mean annual signals), which is assumed to be due to the adapted models and consistent reprocessing
of both series. As two almost independent observing techniques see the same annually recurring signals at almost all co-located
sites, we expect a good geophysical interpretability as integral vertical deformation. For the second part of this paper,
the height time series of 161 suitable GPS sites (of the same solution as before) are used to determine a harmonic and a mean
annual signal for each of them. Comparing the annual signals for this big dataset visually to GRACE-determined load deformations
described in other publications, we find good agreement. This puts emphasis to the assumption that our height data have a
lot of potential to be interpreted as geophysical signals. Out of these 161, 131 are grouped to 55 clusters, if at least two
nearby (some thousand kilometres) sites show similar mean annual signals, which are thus confirmed to be real regional deformation,
not local or technical artefacts. These 55 signals are presented on a “world map” of regional average mean annual height signals,
as easy-to-handle tool to validate geophysical models. The data of these measured regional mean annual signals can be downloaded
from a web-page for numerical analysis. 相似文献
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With the advent of new global navigation satellite systems (GNSSs) and new signals, GNSS users will rely more on them to obtain higher-accuracy positioning. Evil waveform monitoring and assessment are of great importance for GNSS to achieve its positioning, velocity, and timing service with high accuracy. However, the advent of new navigation signals introduces the necessity to extend the traditional analyzing techniques already accepted for binary phase-shift keying modulation to new techniques. First, the well-known second-order step thread model adopted by the International Civil Aviation Organization is introduced. Then the extended new general thread models are developed for the new binary offset carrier modulated signals. However, no research has been done on navigation signal waveform symmetry yet. Simulation results showed that, waveform asymmetry may also cause tracking errors, range biases, and position errors in GNSS receivers. It is thus imperative that the asymmetry be quantified to enable the design of appropriate error budgets and mitigation strategies for various application fields. A novel evil waveform analysis method, called waveform rising and falling edge symmetry (WRaFES) method, is proposed. Based on this WRaFES method, the correlation metrics are provided to detect asymmetric correlation peaks distorted by received signal asymmetry. Then the statistical properties of the proposed methods are analyzed, and a proper deformation detection threshold is calculated. Finally, both simulation results and experimentally measured results of Beidou navigation satellite system (BDS) M1-S B1Cd signal are given, which show the effectiveness and robustness of the proposed thread models. 相似文献
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基于GPS新型L5信号的地表雪深反演研究 总被引:1,自引:0,他引:1
利用GPS多路径反射信号测量地表雪深具有全天候和高时空分辨率的特点,因此其可作为一种代替气象站监测雪深的新手段。然而,先前大多数研究仅使用了GPS L1和L2C波段信噪比数据探测积雪深度。为验证新型的L5信号在雪深反演方面的优越性,本文阐述了GPS-R技术反演雪深的原理,利用Lomb-Scargle周期图法所处理的受积雪表层影响的信噪比数据计算了频谱振幅强度,通过获取频谱特征值与天线高度的关系求解雪深值,最后分别与L1反演结果和实测雪深数据进行了对比。试验结果表明:与现有的GPS-R测量雪深结果相比,利用新型的L5反射信号反演地表雪深的精度更佳;采用GPS-R技术探测雪深对把握测站区域内的雪深变化情况和淡水资源储量具有重要价值。 相似文献
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弱GPS信号捕获算法及其仿真研究 总被引:1,自引:0,他引:1
为满足低信噪比环境下的导航需要,介绍了一种基于改进循环相关的GPS基带信号捕获算法。本文借助于GPS信号基带数学模型以及FFT技术,从理论层面上对捕获算法的信号处理流程以及捕获性能进行了分析;并利用真实GPS基带数据对算法在低信噪比环境下的检测概率和捕获能力进行了重点仿真,仿真结果显示算法在低信噪比环境下是有效的,能够提高低信噪比环境下的检测概率和提高GPS接收机的检测灵敏度。 相似文献
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本文给出了GPS/GLONASS双模接收机的总体设计方案,重点对弱信号环境下的接收机信号捕获进行了讨论,采用并行码相位搜索方法和改进的循环相关算法分别对GLONASS信号和GPS信号进行捕获;并利用真实数据对双模接收机性能进行了仿真研究,重点对接收机捕获弱信号的能力,以及在不同信噪比和不同累加数据长度下的捕获概率进行了讨论,结果表明该双模接收机在不需要较长数据长度的情况下能够捕获低信噪比环境下的卫星导航信号,提高了接收机的灵敏度。 相似文献
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A. G. Pavelyev J. Wickert Y. A. Liou Ch. Reigber T. Schmidt K. Igarashi A. A. Pavelyev S. S. Matyugov 《GPS Solutions》2005,9(2):96-104
A local mechanism for strong ionospheric effects on radio occultation (RO) global positioning satellite system (GPS) signals is described. Peculiar zones centered at the critical points (the tangent points) in the ionosphere, where the gradient of the electron density is perpendicular to the RO ray trajectory, strongly influence the amplitude and phase of RO signals. It follows from the analytical model of local ionospheric effects that the positions of the critical points depend on the RO geometry and the structure of the ionospheric disturbances. Centers of strong ionospheric influence on RO signals can exist, for example, in the sporadic E-layers, which are inclined by 3–6° relative to the local horizontal direction. Also, intense F2 layer irregularities can contribute to the RO signal variations. A classification of the ionospheric influence on the GPS RO signals is introduced using the amplitude data, which indicates different mechanisms (local, diffraction, etc.) for radio waves propagation. The existence of regular mechanisms (e.g., local mechanism) indicates a potential for separating the regular and random parts in the ionospheric influence on the RO signals. 相似文献
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弱GPS信号捕获算法的仿真实验研究 总被引:1,自引:0,他引:1
针对低信噪比环境下导航的需要,文章对低信噪比环境下弱GPS信号捕获算法进行了分析,重点对相关累加、非相关累加以及多重数据位循环相关累加捕获算法的信号处理流程和算法捕获性能进行讨论。通过特定的硬件装置获得真实的GPS信号,利用Matlab对上述3种常用的弱GPS信号捕获算法进行计算机仿真研究。根据理论分析和仿真结果可以看出,多重数据位循环相关捕获算法更适合检测低信噪比环境下的GPS信号。 相似文献
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Considering a GPS satellite and two terrestrial stations, two types of equations are derived relating the heights of the
two stations to the measured data (frequency ratio or clock rate differences) and the coordinates and velocity components
of all three participating objects. The potential possibilities of using such relations for the determination of heights (in
terms of geopotential numbers or orthometric heights) are discussed.
Received: 6 December 2000 / Accepted: 9 July 2001 相似文献
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Yunfeng Tian 《地球空间信息科学学报》2013,16(3):207-215
The nearly nine-year continuous GPS data collected since 1 March 1999 from the Crustal Motion Observation Network of China (CMONOC) were consistently analyzed. Most of the nonlinear movements in the cumulative position time series produced by CMONOC data center disappeared; and more accurate vertical terms and tectonic signals were extracted. Displacements caused by atmospheric pressure loading, nontidal ocean loading, soil moisture mass loading, and snow cover mass loading using the National Centers for Environmental Prediction (NCEP) Reanalysis I/II models and Estimation of the Circulation and Climate of the Ocean (ECCO) data can explain most of the vertical annual terms at many stations, while only parts can be explained at Lhasa and southern coastal sites, indicating that there are some deformation mechanisms that are still unknown or not modeled accurately. The remarkable differences in vertical position time series for short-baseline sites reveal that GPS stations can be greatly affected by local factors; and attention should be paid when explaining observed GPS velocity vectors. 相似文献
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The nearly nine-year continuous GPS data collected since 1 March 1999 from the Crustal Motion Observation Network of China(CMONOC) were consistently analyzed.Most of the nonlinear movements in the cumulative position time series pro-duced by CMONOC data center disappeared;and more accurate vertical terms and tectonic signals were extracted.Displacements caused by atmospheric pressure loading,nontidal ocean loading,soil moisture mass loading,and snow cover mass loading using the National Centers for Environmental Prediction(NCEP) Reanalysis I/II models and Estimation of the Circulation and Climate of the Ocean(ECCO) data can explain most of the vertical annual terms at many stations,while only parts can be explained at Lhasa and southern coastal sites,indicating that there are some deformation mechanisms that are still unknown or not modeled accurately.The remarkable differences in vertical position time series for short-baseline sites reveal that GPS stations can be greatly affected by lo-cal factors;and attention should be paid when explaining observed GPS velocity vectors. 相似文献
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针对现有基于网络和数据流量的实时精密单点定位应用中改正信息传播覆盖范围有限及信号延迟等问题,该文提出了一种新的基于GPS增强信号的实时精密单点定位算法。利用增强频段播发精密轨道、钟差产品有效地解决了传统改正信息传递过程中覆盖范围小与信号延迟的问题,极大地提高了实时改正产品的覆盖范围与时效性。基于亚太地区多个测站准实测数据的实验结果表明:基于LEX增强信息的实时动态和静态精密单点定位解算可分别实现分米级和厘米级的定位精度,显示了利用LEX增强信号进行实时高精度定位的可行性。 相似文献
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Strategies to mitigate aliasing of loading signals while estimating GPS frame parameters 总被引:2,自引:5,他引:2
Although GNSS techniques are theoretically sensitive to the Earth center of mass, it is often preferable to remove intrinsic
origin and scale information from the estimated station positions since they are known to be affected by systematic errors.
This is usually done by estimating the parameters of a linearized similarity transformation which relates the quasi-instantaneous
frames to a long-term frame such as the International Terrestrial Reference Frame (ITRF). It is well known that non-linear
station motions can partially alias into these parameters. We discuss in this paper some procedures that may allow reducing
these aliasing effects in the case of the GPS techniques. The options include the use of well-distributed sub-networks for
the frame transformation estimation, the use of site loading corrections, a modification of the stochastic model by downweighting
heights, or the joint estimation of the low degrees of the deformation field. We confirm that the standard approach consisting
of estimating the transformation over the whole network is particularly harmful for the loading signals if the network is
not well distributed. Downweighting the height component, using a uniform sub-network, or estimating the deformation field
perform similarly in drastically reducing the amplitude of the aliasing effect. The application of these methods to reprocessed
GPS terrestrial frames permits an assessment of the level of agreement between GPS and our loading model, which is found to
be about 1.5 mm WRMS in height and 0.8 mm WRMS in the horizontal at the annual frequency. Aliased loading signals are not
the main source of discrepancies between loading displacement models and GPS position time series. 相似文献
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ZHOU Zhaoming FU Yang XUE Zhengang CUI Hongguang 《地球空间信息科学学报》2006,9(1):24-31
Introduction IthasbeenrecognizedthattheGPSreflected signalshavethepotentialuseforvariousremote sensingpurposesinrecentyears.Someofwhich aremeasurementsofseasurfaceheight,seasur facewindspeedanddirection,oceansignificant waveheight,oceansalinity,landsoilmo… 相似文献