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1.
The Cooperative Network for GIOVE Observation (CONGO) is a global network of real-time capable multi-constellation GNSS receivers,
which has been established by the German Aerospace Center (DLR) and the German Federal Agency for Cartography and Geodesy
(BKG) as a test bed for experimentation with the new Galileo signals. The CONGO network employs a variety of different antennas
and receivers which have become available for public use over the last 2 years. Following an overview of the network and the
employed user equipment, the paper discusses the achieved GPS/GIOVE tracking performance. This includes a characterization
of antenna gain patterns as well as receiver noise and multipath errors. Special attention is given to the discussion of inter-system
biases. The nature and variation of these biases is illustrated based on a set of three different receivers operated in a
zero-baseline configuration at the Wettzell site. 相似文献
2.
伪距多路径误差是影响GNSS导航定位精度的主要误差源之一。多路径误差与接收机周围环境有关,在实际应用中难以建立有效的多路径误差模型进行改正。对于多频GNSS接收机可以通过多频观测值组合估计伪距多路径,但该方法不适用于价格低廉的单频接收机,而导航中使用的大多数为单频接收机。因此,开展单频GNSS伪距多路径误差提取研究具有重要的工程应用价值。本文基于小波分析对单频GNSS接收机伪距多路径误差估计开展研究,首先验证了小波分析用于单频GNSS伪距多路径误差估计的可行性;其次,研究了采用不同的小波基和分解层次对多路径误差估计的影响;最后,研究了改正多路径误差对GNSS定位的影响。实验结果表明不同的小波基和分解层次对多路径误差提取效果没有明显的差别,但小波分解层次较低时定位误差分布相对更加集中,同时,经过多路径误差改正后在NEU3个方向RMS平均改善率达到20.4%、25.1%、16.4%。 相似文献
3.
Though state-of-the-art dual-frequency receivers are employed in the continuous Global Positioning System (CGPS) arrays, the
CGPS coordinate time series are typically very noisy due to the effects of atmospheric biases, multipath, receiver noise,
and so on, with multipath generally being considered the major noise contributor. An adaptive finite-duration impulse response
filter, based on a least-mean-square algorithm, has been developed to derive a relatively noise-free time series from the
CGPS results. Furthermore, this algorithm is suitable for real-time applications.
Numerical simulation studies indicate that the adaptive filters is a powerful signal decomposer, which can significantly mitigate
multipath effects. By applying the filter to both pseudorange and carrier phase multipath sequences derived from some experimental
GPS data, multipath models have been reliably derived. It is found that the best multipath mitigation strategy is forward
filtering using data on two adjacent days, which reduces the standard deviations of the pseudorange multipath time series
to about one fourth its magnitude before correction and to about half in the case of carrier phase. The filter has been successfully
applied to the pseudorange multipath sequences derived from CGPS data. The benefit of this techniques is that the affected
observable sequences can be corrected, and then these corrected observables can be used to improve the quality of the GPS
coordinate results. ? 2000 John Wiley & Sons, Inc. 相似文献
4.
Phase center modeling for LEO GPS receiver antennas and its impact on precise orbit determination 总被引:12,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
5.
基于IGS的L2C信号跟踪站数据验证了具有L2C码的卫星的L2载波的信噪比高于没有L2C码的卫星的L2载波的信噪比,L2载波恢复的数据质量更好.针对不同的接收机,对比分析了C/A码和L2C码多路径效应及观测噪声水平,发现对TRIMBLE NETRS接收机,L2C码误差水平明显高于C/A码,与期望结果相反. 相似文献
6.
In this paper, we present the development of a local area differential GPS testbed of the ground-based augmentation system (GBAS) as the future airport navigation facility in the Taipei Flight Information Region (FIR) in Taiwan. The testbed is mainly a GBAS ground facility, which consists of a ground station, three GBAS receivers, and a VDL (VHF data link) broadcast antenna. We also present an airborne GPS/GBAS prototype receiver in this paper. The airborne subsystem (a GPS/GBAS receiver) receives the correction messages from the ground subsystem to perform a differential GPS (DGPS) positioning. In order to provide an ILS-look-alike approach and landing, the output messages of the airborne receiver are packed in an ARINC 429 format. The proposed airborne system has a software-based global navigation satellite system (GNSS) receiver structure. 相似文献
7.
A multi-technique approach for characterizing the SVN49 signal anomaly, part 2: chip shape analysis 总被引:2,自引:1,他引:1
Steffen Thoelert Michael Meurer Stefan Erker Oliver Montenbruck André Hauschild Pat Fenton 《GPS Solutions》2012,16(1):29-39
Due to a satellite internal reflection at the L5 test payload, the SVN49 (PRN1) GPS satellite exhibits a static multipath
on the L1 and L2 signals, which results in elevation-dependent tracking errors for terrestrial receivers. Using a 30-m high-gain
antenna, code and carrier phase measurements as well as raw in-phase and quadrature radio frequency samples have been collected
during a series of zenith passes in mid-April 2010 to characterize the SVN49 multipath and its impact on common users. Following
an analysis of the receiver tracking data and the IQ constellation provided in Part 1 of this study, the present Part 2 provides
an in-depth investigation into chip shapes for the L1 and L2 signals. A single reflection model is found to be compatible
with the observed chip shape distortions and key parameters for an elevation dependent multipath model are derived. A good
agreement is found between multipath parameters derived independently from raw IQ-samples and measurements of a so-called
Vision Correlator. The chip shapes and their observed variation with elevation can be used to predict the multipath response
of different correlator types within a tracking receiver. The multipath model itself is suitable for implementation in a signal
simulator and thus enables laboratory testing of actual receiver hardware. 相似文献
8.
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
9.
GPS接收机天线相位中心偏差的三维检定研究 总被引:11,自引:1,他引:11
根据GPS接收机天线相位中心的几何关系,在超短基线相对定位法的基础上,利用旋转天线,结合精密水准测量,给出了一种天线相位中心偏差三雏检验的方法。实例表明,该方法具有较高的精度和可靠性,适合于在野外对GPS接收机天线相位中心偏差进行实际检定。 相似文献
10.
Carrier phase multipath is currently one source of unmodeled signals that may bias GPS coordinate time series significantly.
We investigate the effect of simulated carrier phase multipath on time series of several sites covering the period 2002.0–2008.0
and spanning a range of observation geometries. High-, mid-, and low-latitude IGS sites are investigated as well as sites
with significant signal obstructions. We examine the effect of multipath in different sectors of the sky, considering time-constant,
horizontal reflectors at each of 0.1, 0.2, and 1.5 m below the antenna. The differences between a horizontally uniform multipath
source are analyzed, and it is shown that positioning errors are generally larger when unmodeled carrier phase multipath is
azimuthally heterogeneous. Using the adopted multipath model, height biases reach ±1 mm in case of the symmetric multipath
and ±5 mm for the asymmetric multipath but this increases to being ±10 mm in the worst case. In addition to mean bias, low-frequency
variations in the bias also exist, including periodic signals and leading to velocity biases of up to ±0.1 mm/year in the
symmetric case and ±1 mm/year in the asymmetric case over the considered period. In contrast to the generally slowly varying
observation geometry that is typically experienced, we show the effects of an abrupt change in geometry due to receiver/antenna
hardware changes; in the case considered, we see changed pattern of temporal variation in the bias in addition to an instantaneous
offset. 相似文献
11.
12.
13.
An open source GPS multipath simulator in Matlab/Octave 总被引:2,自引:1,他引:1
Multipath is detrimental for both GPS positioning and timing applications. However, the benefits of GPS multipath for reflectometry have become increasingly clear for monitoring soil moisture, snow depth, and vegetation growth. In positioning applications, a simulator can support multipath mitigation efforts in terms of, e.g., site selection, antenna design, receiver performance assessment, and in relating different observations to a common parameterization. For reflectometry, in order to convert observed multipath parameters into useable environmental products, it is important to be able to explicitly link the GPS observables to known characteristics of the GPS receiver/antenna and the reflecting environment. Existing GPS multipath software simulators are generally not readily available for the general scientific community to use and/or modify. Here, a simulator has been implemented in Matlab/Octave and is made available as open source code. It can produce signal-to-noise ratio, carrier phase, and code pseudorange observables, based on L1 and L2 carrier frequencies and C/A, P(Y), and L2C modulations. It couples different surface and antenna types with due consideration for polarization and coherence. In addition to offering predefined material types (water, concrete, soil, etc.), it allows certain dimensional properties to be varied, such as soil moisture and snow density. 相似文献
14.
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
15.
广域差分参考站两种伪距平滑算法的再评估 总被引:4,自引:0,他引:4
广域差分GPS系统(WADGPS)参考站上,需要利用载波相位平滑伪距算法来减小多路径效应的影响。伪距平滑算法有Hatch滤波和加权Hatch滤波两种。文中基于我国WADGPS参考站的实际数据,对这两种平滑算法进行重新评估。实际数据显示,如果不能获得可靠的伪距观测值的方差,在抑制伪距中噪声的影响方面,Hatch滤波明显优于加权Hatch滤波。 相似文献
16.
GLONASS pseudorange inter-channel biases and their effects on combined GPS/GLONASS precise point positioning 总被引:6,自引:5,他引:1
Combined GPS/GLONASS precise point positioning (PPP) can obtain a more precise and reliable position than GPS PPP. However, because of frequency division multiple access, GLONASS carrier phase and pseudorange observations suffer from inter-channel biases (ICBs) which will influence the accuracy and convergence speed of combined GPS/GLONASS PPP. With clear understanding of the characteristics of carrier phase ICBs, we estimated undifferenced GLONASS pseudorange ICBs for 133 receivers from five manufacturers and analyzed their characteristics. In general, pseudorange ICBs corresponding to the same firmware have strong correlations. The ICB values of two receivers with the same firmware may be different because of different antenna types, and their differences are closely related to frequency. Pseudorange ICBs should be provided for each satellite to obtain more precise ICBs as the pseudorange ICBs may vary even on the same frequency. For the solutions of standard point positioning (SPP), after pseudorange ICB calibration, the mean root mean square (RMS) improvements of GLONASS SPP reach up to 57, 48, and 53 % for the East, North, and Up components, while combined GPS/GLONASS SPP reach up to 27, 17, and 23 %, respectively. The combined GPS/GLONASS PPP after pseudorange ICB calibration evidently improved the convergence speed, and the mean RMS of PPP improved by almost 50 % during the convergence period. 相似文献
17.
High-frequency multipath would be problematic for studies at seismic or antenna dynamical frequencies as one could mistakenly
interpret them as signals. A simple procedure to identify high-frequency multipath from global positioning system (GPS) time
series records is presented. For this purpose, data from four GPS base stations are analyzed using spectral analyses techniques.
Additional data, such as TEQC report files of L1 pseudorange multipath, are also used to analyze the high-frequency multipath
and confirmation of the high-frequency multipath inferred from the phase records. Results show that this simple procedure
is effective in identification of high-frequency multipath. The inferred information can aid interpretation of multipath at
the GPS site, and is important for a number of reasons. For example, the information can be used to study GPS site selections
and/or installations.
相似文献
Clement OgajaEmail: |
18.
We have inferred the temperature sensitivity of Dorne Margolin choke ring antennas by direct estimation from differential
clock estimates for two GPS sites separated by 2400 km. At each site, the cable and receiver systems are very well isolated
from environmental variations. By direct comparison of the observed clock variations between these sites with local temperature
measurements, empirical temperature coefficients for each system have been estimated. These thermal coefficients most likely
apply to the only uncontrolled components of the systems, the Dorne Margolin choke ring antennas. Based on these results,
the short-term (diurnal) stability of the antennas appears to be better than 2 ps/°C. The possibility that longer-term effects
exist due to sensitivity in the daily average of the pseudorange observations has not been tested and cannot be excluded.
? 2001 John Wiley & Sons, Inc. 相似文献
19.
We provide a comprehensive overview of pseudorange biases and their dependency on receiver front-end bandwidth and correlator design. Differences in the chip shape distortions among GNSS satellites are the cause of individual pseudorange biases. The different biases must be corrected for in a number of applications, such as positioning with mixed signals or PPP with ambiguity resolution. Current state-of-the-art is to split the pseudorange bias into a receiver- and a satellite-dependent part. As soon as different receivers with different front-end bandwidths or correlator designs are involved, the satellite biases differ between the receivers and this separation is no longer practicable. A test with a special receiver firmware, which allows tracking a satellite with a range of different correlator spacings, has been conducted with live signals as well as a signal simulator. In addition, the variability of satellite biases is assessed through zero-baseline tests with different GNSS receivers using live satellite signals. The receivers are operated with different settings for multipath mitigation, and the changes in the satellite-dependent biases depending on the receivers’ configuration are observed. 相似文献
20.
Forward modeling of GPS multipath for near-surface reflectometry and positioning applications 总被引:4,自引:2,他引:2
Multipath is detrimental for both GPS positioning and timing applications. However, the benefits of GPS multipath for reflectometry have become increasingly clear for soil moisture, snow depth, and vegetation growth monitoring. Most multipath forward models focus on the code modulation, adopting arbitrary values for the reflection power, phase, and delay, or they calculate the reflection delay based on a given geometry and keep reflection power empirically defined. Here, a fully polarimetric forward model is presented, accounting for right- and left-handed circularly polarized components of the GPS broadcast signal and of the antenna and surface responses as well. Starting from the fundamental direct and reflected voltages, we have defined the interferometric and error voltages, which are of more interest in reflectometry and positioning applications. We examined the effect of varying coherence on signal-to-noise ratio, carrier phase, and code pseudorange observables. The main features of the forward model are subsequently illustrated as they relate to the broadcast signal, reflector height, random surface roughness, surface material, antenna pattern, and antenna orientation. We demonstrated how the antenna orientation—upright, tipped, or upside-down—involves a number of trade-offs regarding the neglect of the antenna gain pattern, the minimization of CDMA self-interference, and the maximization of the number of satellites visible. The forward model was also used to understand the multipath signature in GPS positioning applications. For example, we have shown how geodetic GPS antennas offer little impediment for the intake of near-grazing reflections off natural surfaces, in contrast to off metal, because of the lack of diversity with respect to the direct signal—small interferometric delay and Doppler, same sense of polarization, and similar direction of arrival. 相似文献