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1.
多径误差指间接波对直接波的破坏性干涉而引起的接收机与卫星的距离误差,具有时变特性,难以通过模型改正或差分技术等方法予以消除. 但在存在多径干扰的情况下,同一颗卫星不同频率上的信噪比会发生波动,基于该特征,本文提出一种用信噪比检测多径误差的方法:基于北斗卫星导航系统（BDS）三频信噪比的多径误差数据,建立一个关于信噪比的统计量Ssa?(实验环境)以及计算开阔环境(低多径环境)的检测阈值T,通过比较Ssa 与T的大小关系来检测BDS卫星多径误差. 实验结果表明:该方法可以有效探测BDS卫星多径误差,并基于检测阈值和位置精度因子(PDOP)的变化对该某段时间内的卫星予以剔除,获得更好的定位效果. 相似文献
2.
多径误差是全球卫星导航系统（global navigation satellite system,GNSS）高精度实时定位的主要误差源。由于多径效应具有时变特性且与观测环境有关,难以有效探测与剔除,尤其是动态定位领域。鉴于多径效应对于同颗卫星不同频率观测值影响不同,本文采用三频信噪比（signal-noise ratio,SNR）频率间差分数据,设计算法探测北斗对地静止卫星（geostationary orbit satellite,GEO）多径误差,并依据开阔环境SNR频间差分数据序列进行统计分析,确定其探测阈值。实验结果表明,北斗GEO卫星易受多径误差影响,传统方法难以实时有效探测,本文提出的新方法可有效探测GEO多径误差,并基于设定的阈值对其数据进行降权或剔除,可应用于GNSS数据质量控制。 相似文献
3.
4.
Markus Irsigler 《GPS Solutions》2010,14(4):305-317
A well-known effect of multipath propagation is multipath fading that typically causes periodic signal variations. Such signal
variations may become visible in some basic GNSS observables such as the code minus carrier observable, single or double differences
or in C/N
0 time series. The frequency of these variations—also called fading frequency or multipath phase rate—strongly depends on the
multipath environment, i.e. on the actual geometric conditions which can be described by the location of the satellite causing
the multipath signal and the reflector location with respect to the receiving antenna. This paper gives a detailed insight
on the expected multipath phase rates in different multipath environments. Different geometric conditions are analyzed, from
arbitrary reflector positions to the point of dealing with the special case of ground multipath. Fading frequencies are determined
by means of an empirical approach using the characteristics of real satellite passes. The approach results in distributions
of multipath phase rates which are computed for a multitude of possible reflector locations and from which minimum, mean and
maximum multipath phase rates can be derived. 相似文献
5.
在全球导航卫星系统(Global Navigation Satellite System,GNSS)接收机附近的反射、衍射、干扰信号等所造成的多路径效应是影响定位的主要误差来源。信噪比(Signal-Noise Ratio,SNR)的振荡是由多路径信号叠加在直接信号上引起的,基于此原理学者们提出了很多检测和缓解多路径误差的方法。本文通过谱分析的方法对多路径时间序列进行了分析,并研究多路径与信噪比之间的相关性,对基于信噪比检测和缓解多路径误差的方法的适用性进行了说明。实验表明:多路径和信噪比振荡值的时间序列具有显著的相关性,能够利用信噪比观测值削弱多路径影响。 相似文献
6.
NLOS GPS signal detection using a dual-polarisation antenna 总被引：2，自引：2，他引：0
The reception of indirect signals, either in the form of non-line-of-sight (NLOS) reception or multipath interference, is a major cause of GNSS position errors in urban environments. We explore the potential of using dual-polarisation antenna technology for detecting and mitigating the reception of NLOS signals and severe multipath interference. The new technique computes the value of the carrier-power-to-noise-density (C/N 0) measurements from left-hand circular polarised outputs subtracted from the right-hand circular polarised C/N 0 counterpart. If this quality is negative, NLOS signal reception is assumed. If the C/N 0 difference is positive, but falls below a threshold based on its lower bound in an open-sky environment, severe multipath interference is assumed. Results from two experiments are presented. Open-field testing was first performed to characterise the antenna behaviour and determine a suitable multipath detection threshold. The techniques were then tested in a dense urban area. Using the new method, two signals in the urban data were identified as NLOS-only reception during the occupation period at one station, while the majority of the remaining signals present were subject to a mixture of NLOS reception and severe multipath interference. The point positioning results were dramatically improved by excluding the detected NLOS measurements. The new technique is suited to a wide range of static ground applications based on our results. 相似文献
7.
介绍了L5载波的特点,分析了L5载波对GPS测量的影响,用实测数据分析了三频载波的信噪比及各个民用码的噪声水平。 相似文献
8.
利用GNSS-MR(Global Navigation Satellite System Multipath Reflectometry)技术反演积雪深度是近年来一种新兴的卫星遥感技术。目前大多数研究仅使用GPS(Global Position System)数据限制了该技术的发展,为了扩展GNSS-MR算法的应用,介绍了基于GNSS-MR算法的雪深反演模型。首先,通过多项式拟合分解GLONASS观测数据获取高精度的信噪比残差序列;然后,利用Lomb-Scargle谱分析法对其进行频谱分析可解算雪深值。选取IGS中心的YEL2站2015年11月到2016年6月共243天的GLONASS卫星L1波段反射信号的SNR数据进行实例分析,并以美国国家气象数据中心提供的加拿大Y-H (Yellowknife Henderson)气象站的实测雪深数据为真值,将反演雪深与实测雪深进行对比验证。所得实验结果如下:(1)与GPS卫星的反演值相比,基于GLONASS-MR(GLONASS Multipath Reflectometry)技术反演积雪深度的精度同样能达到厘米级,RMSE仅3.3 cm,反演值与实测值的空间分布趋势一致且相关性较强,其相关系数R2高达0.969;(2)不同的积雪深度对信噪比的振幅频率与垂直反射距离具有直接影响;(3)对同一卫星而言,信噪比的频谱振幅强度峰值与其对应的反演值存在线性相关;(4)在相同条件下,采用多颗GLONASS卫星数据比单颗GLONASS卫星数据反演雪深的效果明显更优。基于反演的高时间分辨率产品,分析该地区雪深日变化的情况,实验结果表明基于陆基CORS站的GLONASS-MR技术在用于实时、连续的雪深变化监测方面具有良好的潜力和可行性。 相似文献
9.
Much of the research into multipath detection and mitigation has not considered the carrier phase delay between the line of
sight (LOS) and reflected signals. A new variable referred to as early late phase (ELP) has recently been proposed to exploit
this phase difference. It has been found that in a receiver tracking the L1 GPS signal, the probability of detecting multipath
is lower when the carrier phase difference between the LOS and a reflected signal is an integer multiple of π. Since the pseudorange
error caused by the multipath’s presence is the highest in this case, we propose to exploit the coexistence of another GPS
civilian signal, the L2C. We present an analysis of ELP for the L1 and L2C signals, and a combination of both, for detecting
multipath. The multipath detection performance has been compared using probabilities of false alarm and detection. An ideal
algorithm should have lower probability of false alarm and higher probability of detection. However, it has been found that
using dual-frequency ELP increases both probabilities. Thus, receiver operator characteristics (ROC) curves, and the area
under the ROC curves, have been used for effective comparison. It has been found that the L2C signal individually gives worse
performance than L1 because of its weaker signal strength. However, the combination of L1 and L2C gives the best overall performance,
and thus it can be claimed that ELP using dual-frequency receivers is a more effective approach for detecting multipath. 相似文献
10.
通过载噪比(CNR)、数据完整率、伪距与载波相位观测值噪声和伪距多路径效应四个指标对北斗三号卫星导航系统(BDS-3)新频点B1C/B2a车载动态数据的特性进行了分析,测试了BDS-3新频点动态精密单点定位(PPP)的性能,并与其它全球卫星导航系统(GNSS)进行了对比. 试验结果表明,BDS-3新频点B2a平均CNR优于北斗卫星导航系统(BDS)其它频率,但略差于GPS L5;相较于其它GNSS,BDS数据完整率相对较高,其中BDS-3 B2a新频点数据完整率最高;BDS-3 B2b伪距观测值噪声最小,B1C和B2a伪距观测值噪声约为B2b信号的3倍,但不同频率相位观测值噪声处于同一量级;对于伪距多路径而言,BDS-3 B1C/B2a 信号略小于B2b 信号. 总体而言,GPS L5信号抑制多路径效应的能力最强. 在动态PPP性能方面,BDS-3 B1C/B2a双频组合动态PPP定位精度最优,其三维(3D)均方根(RMS)误差为0.439 m,相比BDS B1I/B3I、GPS L1/L2、GLONASS G1/G2和Galileo E1/E5a双频组合PPP,其精度改善率分别为49%、56%、81%和42%. 相似文献
11.
Real-time cycle slip detection in triple-frequency GNSS 总被引：7，自引：2，他引：5
The modernization of the global positioning system and the advent of the European project Galileo will lead to a multifrequency global navigation satellite system (GNSS). The presence of new frequencies introduces more degrees of freedom in the GNSS data combination. We define linear combinations of GNSS observations with the aim to detect and correct cycle slips in real time. In particular, the detection is based on five geometry-free linear combinations used in three cascading steps. Most of the jumps are detected in the first step using three minimum-noise combinations of phase and code observations. The remaining jumps with very small amplitude are detected in the other two steps by means of two-tailored linear combinations of phase observations. Once the epoch of the slip has been detected, its amplitude is estimated using other linear combinations of phase observations. These combinations are defined with the aim of discriminating between the possible combinations of jump amplitudes in the three carriers. The method has been tested on simulated data and 1-second triple-frequency undifferenced GPS data coming from a friendly multipath environment. Results show that the proposed method is able to detect and repair all combinations of cycle slips in the three carriers. 相似文献
12.
Peter F. de Bakker Christian C. J. M. Tiberius Hans van der Marel Roel J. P. van Bree 《GPS Solutions》2012,16(1):53-64
Stochastic properties of GNSS range measurements can accurately be estimated using a geometry-free short and zero baseline
analysis method. This method is now applied to dual-frequency measurements from a new field campaign. Results are presented
for the new GPS L5Q and GIOVE E5aQ wideband signals, in addition to the GPS L1 C/A and GIOVE E1B signals. As expected, the
results clearly show the high precision of the new signals, but they also show, rather unexpectedly, significant, slowly changing
variations in the pseudorange code measurements that are probably a result of strong multipath interference on the data. Carrier
phase measurement noise is assessed on both frequencies, and finally successful mixed GPS-GIOVE double difference ambiguity
resolution is demonstrated. 相似文献
13.
A multi-technique approach for characterizing the SVN49 signal anomaly, part 1: receiver tracking and IQ constellation 总被引：3，自引：1，他引：2
André Hauschild Oliver Montenbruck Steffen Thoelert Stefan Erker Michael Meurer Javad Ashjaee 《GPS Solutions》2012,16(1):19-28
A characterization of the signal anomaly of SVN49 is presented. A mathematical model is developed to relate the observed multipath
to the internal signal reflection. The analyses provided are based on measurements, which have been collected during a dedicated
tracking campaign with a 30-m dish antenna. Data on the L1 and L2 frequency have been collected with four different receivers.
In addition, IQ samples have been recorded directly with a spectrum analyzer. The multipath combination of the receiver measurements
on L1 and L2 is analyzed to demonstrate the effect of the signal reflections on different correlator spacing. The capability
to suppress the signal reflection with receiver multipath mitigation methods is demonstrated. Finally, preliminary estimates
of the attenuation, delay, and phase shift over elevation are obtained from an IQ sample analysis. 相似文献
14.
The wavelet transform is used to reduce the high frequency multipath of pseudorange and carrier phase GPS double differences (DDs). This transform decomposes the DD signal, thus separating the high frequencies due to multipath effects. After the decomposition, the wavelet shrinkage is performed by thresholding to eliminate the high frequency component. Then the signal can be reconstructed without the high frequency component. We show how to choose the best threshold. Although the high frequency multipath is not the main multipath error component, its correction provides improvements of about 30% in pseudorange average residuals and 24% in carrier phases. The results also show that the ambiguity solutions become more reliable after correcting the high frequency multipath. 相似文献
15.
Multipath remains one of the major challenges in Global Navigation Satellite System (GNSS) positioning because it is considered the dominant source of ranging errors, which can be classified into specular and diffuse types. We present a new method using wavelets to extract the pseudorange multipath in the time domain and breaking it down into the two components. The main idea is an analysis-reconstruction approach based on application of both continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The proposed procedure involves the use of L1 code-minus-carrier (CMC) observable where higher-frequency terms are isolated as residuals. CMC residuals are analyzed by applying the CWT, and we propose the scalogram as a technique for discerning time–frequency variations of the multipath signal. Unlike Fourier transform, the potential of the CWT scalogram for examining the non-stationary and multifrequency nature of the multipath is confirmed as it simultaneously allows fine detection and time localization of the most representative frequencies of the signal. This interpretation of the CWT scalogram is relevant when choosing the levels of reconstruction with DWT, allowing accurate time domain extraction of both the specular and diffuse multipath. The performance and robustness of the method and its boundary applicability are assessed. The experiment was carried out using a receiver of Campania GNSS Network. The results are given in which specular multipath error is achieved using DWT level 7 approximation component and diffuse multipath error is achieved using DWT level 6 denoised detail component. 相似文献
16.
本文基于扩频信号分析了不同多径参数对载波幅度和相位的影响,在低信噪比条件下,使用自适应均衡技术,实时估计多径参数和抑制载波多径。使用实时估计得到的多径参数,重构多径信号,从接受信号中消去多径信号。仿真结果表明,这2种算法均能很好地降低多径对载波的影响,可以有效提高载波相位的测量精度。 相似文献
17.
Carrier phase ambiguity resolution on the fly is investigated using two receiver technologies, namely dual-frequency P code and high performance, single frequency, C/A code receivers. Both receiver types were used simultaneously in a series of land kinematic trials. A least-squares search technique is used to find the correct double difference carrier phase ambiguities. Both C/A and single frequency P code technologies are found to be equivalent and capable of resolving the integer ambiguities on the fly using some 30 to 200 seconds of data under benign multipath conditions. Successful ambiguity resolution on the fly results in cm-level accuracy kinematic positioning. The ambiguity resolution time required and success rate are however found to be strongly dependent on the level of carrier phase multipath and, as a consequence, on the error variance assigned to the carrier phase measurements. The use of widelaning with the dual frequency P code results in ambiguity resolution in seconds. The performance of widelaning is also superior in a comparatively high carrier phase multipath environment. 相似文献
18.
Multipath in global positioning system (GPS) is the interference of the microwave signals directly from satellites and those
reflected before reaching the antenna, typically by the ground. Because reflected signals cause positioning errors, GPS antennas
are designed to reduce such interference. Recent studies show that multipath could be utilized to infer the properties of
the ground around the antenna. Here, we report one such application, i.e. a fixed GPS station used as a snow depth meter.
Because the satellite moves in the sky, the excess path length of reflected waves changes at rates dependent on the antenna
height. This causes quasi-periodic variations of the amplitude and phase of the received signals. Accumulation of snow reduces
effective antenna heights, and we can see it by analyzing multipath signatures. Signal-to-noise ratios (SNR) are often used
to analyze multipath, but they are not always available in raw GPS data files. Here, we demonstrate that the geometry-free
linear combination (L4), normally used to study the ionosphere, can also be used to analyze multipath signatures. We obtained
snow depth time series at a GPS station in Hokkaido, Japan, from January to April in 2009 using L4 and SNR. Then, we compared
their precisions. We also discuss mechanisms responsible for the possible underestimation of the snow depth by GPS. Finally,
we investigate the possibility of inferring physical conditions of the snow surface using amplitudes of multipath signatures. 相似文献
19.
Jean-Philippe Montillet Lukasz K. Bonenberg Craig M. Hancock Gethin W. Roberts 《GPS Solutions》2014,18(2):273-282
This work focuses on the performances of Locata technology in single point positioning using different firmware versions (v2.0 and v4.2). The main difference is that the Locata transmitters with firmware v2.0 are single frequency, whereas in the v4.2, they are dual frequency. The performance of the different firmware versions has been measured in different environments including an urban canyon-like environment and a more open environment on the roof of the Nottingham Geospatial Building. The results obtained with firmware v4.2 show that with more available signals, cycle slips can be more easily detected, together with the improvement of the detection of multipath fading on the received signal. As a result, the noise level on the carrier phase measurements recorded with firmware v4.2 is equal on average to a third of the level of noise on the measurements recorded with firmware v2.0. In addition, with either firmware, the accuracy of the position is at the sub-centimeter level on the East and North coordinates. The Up coordinate accuracy is generally less accurate and more sensitive to the geometry of the network in our experiments. We then show the importance of the geometry of the Locata network on the accuracy of Locata positioning system through the demonstration of the relationship between the dilution of precision value and the confidence ellipse. We also demonstrate that the model of the noise on the Locata coordinates is a white Gaussian noise with the help of the autocorrelation function. To some extent, this technique can help to detect whether the Wi-Fi technology is interfering with the Locata technology and degrades the positioning accuracy. 相似文献
20.
Geometry-free undifferenced, single and double differenced analysis of single frequency GPS, EGNOS and GIOVE-A/B measurements 总被引：2，自引：1，他引：2
This paper demonstrates a geometry-free GNSS measurement analysis approach and presents results of single frequency GPS, EGNOS
and GIOVE short and zero baseline measurements. The purpose is to separate the different contributions to the measurement
noise of pseudo range code and carrier phase observations at the receiver. The influence of multipath on the different combinations
of observations is also determined. Quantitative results are presented for the thermal code and phase measurement noise and
for the correlation between the observations. Comparison of the results with theoretical approximations confirms the validity
of the used approach. Results from field measurements clearly show less thermal noise on the Galileo E1BC observations than
on the GPS L1C/A observations due to the new signal modulation. The feasibility of ambiguity resolution with a geometry-free
model is also discussed including the significant impact of multipath thereon. 相似文献