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1.
The problem of phase ambiguity resolution in global positioning system (GPS) theory is considered. The Bayesian approach
is applied to this problem and, using Monte Carlo simulation to search over the integer candidates, a practical expression
for the Bayesian estimator is obtained. The analysis of the integer grid points inside the search ellipsoid and their evolution
with time, while measurements are accumulated, leads to the development of a Bayesian theory based on a mathematical mixture
model for the ambiguity.
Received: 29 March 2001 / Accepted: 3 September 2001 相似文献
2.
The global positioning system (GPS) model is distinctive in the way that the unknown parameters are not only real-valued,
the baseline coordinates, but also integers, the phase ambiguities. The GPS model therefore leads to a mixed integer–real-valued
estimation problem. Common solutions are the float solution, which ignores the ambiguities being integers, or the fixed solution,
where the ambiguities are estimated as integers and then are fixed. Confidence regions, so-called HPD (highest posterior density)
regions, for the GPS baselines are derived by Bayesian statistics. They take care of the integer character of the phase ambiguities
but still consider them as unknown parameters. Estimating these confidence regions leads to a numerical integration problem
which is solved by Monte Carlo methods. This is computationally expensive so that approximations of the confidence regions
are also developed. In an example it is shown that for a high confidence level the confidence region consists of more than
one region.
Received: 1 February 2001 / Accepted: 18 July 2001 相似文献
3.
Precise estimation of residual tropospheric delays using a regional GPS network for real-time kinematic applications 总被引：7，自引：0，他引：7
A new method called Trop_NetAdjust is described to predict in real time the residual tropospheric delays on the GPS carrier
phase observables using the redundant measurements from a network of GPS reference stations. This method can not only enhance
the effectiveness and reliability of real-time kinematic users within the network, but also provide a valid approach to tropospheric
parameter variation forecasting. Trop_NetAdjust is theoretically based upon LS prediction criteria and enables the prediction
of residual tropospheric delays remaining after a standard model has been applied to the raw GPS measurements. Two cases are
analyzed, namely a first case when the delay is required for an existing satellite at a new point within the network and a
second case when the delay is required for a new satellite. Field tests were conducted using data collected in a network of
11 reference stations covering a 400×600 km region in southern Norway. The results were analyzed in the measurement domain
(ionospheric-free double-difference residuals) and showed improvements of 20 to 65% RMS errors using Trop_NetAdjust. The estimates
of the Trop_NetAdjust prediction accuracy were also obtained using the covariance analysis method. The agreement was consistently
better than 30% when compared with data from a real network.
Received: 28 February 2000 / Accepted: 9 January 2001 相似文献
4.
Prediction of surface horizontal displacements, and gravity and tilt changes caused by filling the Three Gorges Reservoir 总被引：11，自引：0，他引：11
Horizontal displacements, and gravity and tilt changes induced by filling the Three Gorges Reservoir are modeled using elastic
loading Green functions. When the water surface reaches its highest level, the effects become maximum on the reservoir banks.
The longitudinal and latitudinal components of the horizontal displacements reach −8.2 and 7.7 mm respectively, gravity is
increased by up to 3.4 mGal, and the prime vertical and meridian components of the tilt changes are −7.8 and −17.5 arcseconds
respectively. Accordingly, the filling of the reservoir will influence values observed from global positioning system (GPS),
gravimetry and tilt measurements in the area. The results given can be used to provide important corrections for extracting
earthquake-related signals from observed data.
Received: 19 January 2001 / Accepted: 3 September 2001 相似文献
5.
Three different methods of handling topography in geoid determination were investigated. The first two methods employ the
residual terrain model (RTM) remove–restore technique, yielding the quasigeoid, whereas the third method uses the classical
Helmert condensation method, yielding the geoid. All three methods were used with the geopotential model Earth Gravity Model
(1996) (EGM96) as a reference, and the results were compared to precise global positioning system (GPS) levelling networks
in Scandinavia. An investigation of the Helmert method, focusing on the different types of indirect effects and their effects
on the geoid, was also carried out. The three different methods used produce almost identical results at the 5-cm level, when
compared to the GPS levelling networks. However, small systematic differences existed.
Received: 18 March 1999 / Accepted: 21 March 2000 相似文献
6.
Regularization of geopotential determination from satellite data by variance components 总被引：11，自引：18，他引：11
Different types of present or future satellite data have to be combined by applying appropriate weighting for the determination
of the gravity field of the Earth, for instance GPS observations for CHAMP with satellite to satellite tracking for the coming
mission GRACE as well as gradiometer measurements for GOCE. In addition, the estimate of the geopotential has to be smoothed
or regularized because of the inversion problem. It is proposed to solve these two tasks by Bayesian inference on variance
components. The estimates of the variance components are computed by a stochastic estimator of the traces of matrices connected
with the inverse of the matrix of normal equations, thus leading to a new method for determining variance components for large
linear systems. The posterior density function for the variance components, weighting factors and regularization parameters
are given in order to compute the confidence intervals for these quantities. Test computations with simulated gradiometer
observations for GOCE and satellite to satellite tracking for GRACE show the validity of the approach.
Received: 5 June 2001 / Accepted: 28 November 2001 相似文献
7.
G. Even-Tzur 《Journal of Geodesy》2002,76(8):455-461
The performance of geodetic monitoring networks is heavily influenced by the configuration of the measured GPS vectors. As
an effective design of the GPS measurements will decrease GPS campaign costs and increase the accuracy and reliability of
the entire network, the identification of the preferred GPS vectors for measurement has been highlighted as a core problem
in the process of deformation monitoring. An algorithm based on a sensitivity analysis of the network, as dependent upon a
postulated velocity field, is suggested for the selection of the optimal GPS vectors. Relevant mathematical and statistical
concepts are presented as the basis for an improved method of vector configuration design. A sensitivity analysis of the geodetic
geodynamic network in the north of Israel is presented, where the method is examined against two deformation models, the Simple
Transform Fault and the Locked Fault. The proposed method is suggested as a means for the improvement of the design of monitoring
networks, a common practice worldwide.
Received: 30 July 2001 / Accepted: 3 June 2002
Acknowledgments. It is my pleasant duty to thank the Survey of Israel and Dr. E. Ostrovsky for providing the variance–covariance matrix of
the G1 network in northern Israel. I would like to thank the reviewers of this paper for their constructive and helpful remarks. 相似文献
8.
The long-wavelength geoid errors on large-scale geoid solutions, and the use of modified kernels to mitigate these effects,
are studied. The geoid around the Nordic area, from Greenland to the Ural mountains, is considered. The effect of including
additional gravity data around the Nordic/Baltic land area, originating from both marine, satellite and ground-based measurements,
is studied. It is found that additional data appear to increase the noise level in computations, indicating the presence of
systematic errors. Therefore, the Wong–Gore modification to the Stokes kernel is applied. This method of removing lower-order
terms in the Stokes kernel appears to improve the geoid. The best fit to the global positioning system (GPS) leveling points
is obtained with a degree of modification of approximately 30. In addition to the study of modification errors, the results
of different methods of combining satellite altimetry gravity and other gravimetry are presented. They all gave comparable
results, at the 6-cm level, when evaluated for the Nordic GPS networks. One dimensional (1-D) and 2-D fast Fourier transform
(FFT) methods are also compared. It is shown that even though methods differ by up to 6 cm, the fit to the GPS is essentially
the same. A surprising conclusion is that the addition of more data does not always produce a better geoid, illustrating the
danger of systematic errors in data.
Received: 4 July 2001 / Accepted: 21 February 2002 相似文献
9.
A global plate motion model is established based on the ITRF97 velocity fields and geological model NUVEL1. Sub-plate models
are estimated by using the velocity fields derived from 45 global positioning system (GPS) sites under the ITRF97 reference
frame in China. Comparisons between space geodesy and geological models are given. It is found that the Euler vector of the
AFRC–EURA pair has an obvious discrepancy between space geodetic and geological models. The motion patterns of tectonic blocks
in China predicted by GPS are consistent with those of geological data on the whole.
Received: 9 November 2000 / Accepted: 17 September 2001 相似文献
10.
11.
P. J. G. Teunissen 《Journal of Geodesy》2001,75(7-8):399-407
Carrier phase ambiguity resolution is the key to fast and high-precision GNSS (Global Navigation Satellite System) kinematic
positioning. Critical in the application of ambiguity resolution is the quality of the computed integer ambiguities. Unsuccessful
ambiguity resolution, when passed unnoticed, will too often lead to unacceptable errors in the positioning results. Very high
success rates are therefore required for ambiguity resolution to be reliable. Biases which are unaccounted for will lower
the success rate and thus increase the chance of unsuccessful ambiguity resolution. The performance of integer ambiguity estimation
in the presence of such biases is studied. Particular attention is given to integer rounding, integer bootstrapping and integer
least squares. Lower and upper bounds, as well as an exact and easy-to-compute formula for the bias-affected success rate,
are presented. These results will enable the evaluation of the bias robustness of ambiguity resolution.
Received: 28 September 2000 / Accepted: 29 March 2001 相似文献
12.
GPS-based precise orbit determination of the very low Earth-orbiting gravity mission GOCE 总被引：5，自引：0，他引：5
A prerequisite for the success of future gravity missions like the European Gravity field and steady-state Ocean Circulation
Explorer (GOCE) is a precise orbit determination (POD). A detailed simulation study has been carried out to assess the achievable
orbit accuracy based on satellite-to-satellite tracking (SST) by the US global positioning system (GPS) and in conjunction
the implications for gravity field determination. An orbit accuracy at the few centimeter level seems possible, sufficient
to support the GOCE gravity mission and in particular its gravity gradiometer.
Received: 21 January 2000 / Accepted: 4 July 2000 相似文献
13.
R. Dach G. Beutler U. Hugentobler S. Schaer T. Schildknecht T. Springer G. Dudle L. Prost 《Journal of Geodesy》2003,77(1-2):1-14
A joint time-transfer project between the Astronomical Institute of the University of Berne (AIUB) and the Swiss Federal
Office of Metrology and Accreditation (METAS) was initiated to investigate the power of the time transfer using GPS carrier
phase observations. Studies carried out in the context of this project are presented. The error propagation for the time-transfer
solution using GPS carrier phase observations was investigated. To this purpose a simulation study was performed. Special
interest was focussed on errors in the vertical component of the station position, antenna phase-center variations and orbit
errors. A constant error in the vertical component introduces a drift in the time-transfer results for long baselines in east–west
directions. The simulation study was completed by investigating the profit for time transfer when introducing the integer
carrier phase ambiguities from a double-difference solution. This may reduce the drift in the time-transfer results caused
by constant vertical error sources. The results from the present time-transfer solution are shown in comparison to results
obtained with independent time-transfer techniques. The interpretation of the comparison benefits from the investigations
of the error propagation study. Two types of solutions are produced on a regular basis at AIUB: one based on the rapid orbits
from CODE, the other on the CODE final orbits. The rapid solution is available the day after the observations and has nearly
the same quality as the final solution, which has a latency of about one week. The differences between these two solutions
are below the nanosecond level. The differences from independent time-transfer techniques such as TWSTFT (two-way satellite
time and frequency transfer) are a few nanoseconds for both products.
Received: 15 November 2001 / Accepted: 6 September 2002
Correspondence to:R. Dach 相似文献
14.
An approach to GLONASS ambiguity resolution 总被引：9，自引：2，他引：7
J. Wang 《Journal of Geodesy》2000,74(5):421-430
When processing global navigation satellite system (GLONASS) carrier phases, the standard double-differencing (DD) procedure
cannot cancel receiver clock terms in the DD phase measurement equations due to the multiple frequencies of the carrier phases.
Consequently, a receiver clock parameter has to be set up in the measurement equations in addition to baseline components
and DD ambiguities. The resulting normal matrix unfortunately becomes singular. Methods to deal with this problem have been
proposed in the literature. However, these methods rely on the use of pseudo-ranges. As pseudo-ranges are contaminated by
multi-path and hardware delays, biases in these pseudo-ranges are significant, which may result in unreliable ambiguity resolution.
A new approach is addressed that is not sensitive to the biases in the pseudo-ranges. The proposed approach includes such
steps as converting the carrier phases to their distances to cancel the receiver clock errors, and searching for the most
likely single-differenced (SD) ambiguity. Based on the results from the theoretical investigation, a practical procedure for
GLONASS ambiguity resolution is presented. The initial experimental results demonstrate that the proposed approach is useable
in cases of GLONASS and combined global positioning system (GPS) and GLONASS positioning.
Received: 19 August 1998 / Accepted: 12 November 1999 相似文献
15.
In October 1998 the IGEX field campaign, the first coordinated international effort to monitor GLONASS satellites on global
basis, was started. Currently about 40 institutions worldwide support this effort either by providing GLONASS tracking data
or in operating related data and analysis centers. The increasing quality and consistency of the calculated GLONASS orbits
(about 25 cm early in 2000), even after the end of the official IGEX field campaign, are shown. Particular attention is drawn
to the combination of precise ephemerides in order to generate a robust, reliable and complete IGEX orbits product. Some problems
in modeling the effect of solar radiation pressure on GLONASS satellites are demonstrated. Finally, the expected benefits
and prospects of the upcoming International GLOnass Service-Pilot Project (IGLOS-PP) of the International GPS Service (IGS)
are discussed in more detail.
Received: 17 August 2000 / Accepted: 12 April 2001 相似文献
16.
Until recently, the Global Positioning System (GPS) was the only operational means of distributing time to an arbitrary number
of users and of synchronizing clocks over large distances with a high degree of precision and accuracy. Over the last few
years it has been shown that similar performance can be achieved using the Russian Global Navigation Satellite System (GLONASS).
GLONASS time transfer between continents was initially hampered by the lack of post-processed precise ephemerides. Results
from the International GLONASS Experiment (IGEX) campaign are now available, however, and this paper reports on the first
use of IGEX precise ephemerides for GLONASS P-code intercontinental time links. The results of GLONASS P-code and GPS C/A-code
time transfer are compared under similar conditions.
Received: 31 January 2000 / Accepted: 10 July 2000 相似文献
17.
An algorithm for very accurate absolute positioning through Global Positioning System (GPS) satellite clock estimation has
been developed. Using International GPS Service (IGS) precise orbits and measurements, GPS clock errors were estimated at
30-s intervals. Compared to values determined by the Jet Propulsion Laboratory, the agreement was at the level of about 0.1 ns
(3 cm). The clock error estimates were then applied to an absolute positioning algorithm in both static and kinematic modes.
For the static case, an IGS station was selected and the coordinates were estimated every 30 s. The estimated absolute position
coordinates and the known values had a mean difference of up to 18 cm with standard deviation less than 2 cm. For the kinematic
case, data obtained every second from a GPS buoy were tested and the result from the absolute positioning was compared to
a differential GPS (DGPS) solution. The mean differences between the coordinates estimated by the two methods are less than
40 cm and the standard deviations are less than 25 cm. It was verified that this poorer standard deviation on 1-s position
results is due to the clock error interpolation from 30-s estimates with Selective Availability (SA). After SA was turned
off, higher-rate clock error estimates (such as 1 s) could be obtained by a simple interpolation with negligible corruption.
Therefore, the proposed absolute positioning technique can be used to within a few centimeters' precision at any rate by estimating
30-s satellite clock errors and interpolating them.
Received: 16 May 2000 / Accepted: 23 October 2000 相似文献
18.
Due to the different signal frequencies for the GLONASS satellites, the commonly-used double-differencing procedure for carrier phase data processing can not be implemented in its straightforward form, as in the case of GPS. In this paper a novel data processing strategy, involving a three-step procedure, for integrated GPS/GLONASS positioning is proposed. The first is pseudo-range-based positioning, that uses double-differenced (DD) GPS pseudo-range and single-differenced (SD) GLONASS pseudo-range measurements to derive the initial position and receiver clock bias. The second is forming DD measurements (expressed in cycles) in order to estimate the ambiguities, by using the receiver clock bias estimated in the above step. The third is to form DD measurements (expressed in metric units) with the unknown SD integer ambiguity for the GLONASS reference satellite as the only parameter (which is constant before a cycle slip occurs for this satellite). A real-time stochastic model estimated by residual series over previous epochs is proposed for integrated GPS/GLONASS carrier phase and pseudo-range data processing. Other associated issues, such as cycle slip detection, validation criteria and adaptive procedure(s) for ambiguity resolution, is also discussed. The performance of this data processing strategy will be demonstrated through case study examples of rapid static positioning and kinematic positioning. From four experiments carried out to date, the results indicate that rapid static positioning requires 1 minute of single frequency GPS/GLONASS data for 100% positioning success rate. The single epoch positioning solution for kinematic positioning can achieve 94.6% success rate over short baselines (<6 km). 相似文献
19.
The parameter distributions of the integer GPS model 总被引：6，自引：0，他引：6
P. J. G. Teunissen 《Journal of Geodesy》2002,76(1):41-48
A parameter estimation theory is incomplete if no rigorous measures are available for describing the uncertainty of the parameter
estimators. Since the classical theory of linear estimation does not apply to the integer GPS model, rigorous probabilistic
statements cannot be made with reference to the classical results. The fact that integer parameters are involved in the estimation
process forces a reappraisal of the propagation of uncertainty. It is with this purpose in mind that the joint and marginal
distributional properties of both the integer and non-integer parameters of the GPS model are determined. These joint distributions
can also be used to determine the distribution of functions of the parameters. As an important example, the distribution of
the vector of ambiguity residuals is determined.
Received: 30 January 2001 / Accepted: 31 July 2001 相似文献
20.
The New Hebrides experiment consisted of setting up a pair of DORIS beacons in remote tropical islands in the southwestern
Pacific, between 1993 and 1997. Because of orbitography requirements on TOPEX/Poséidon, the beacons were only transmitting
to SPOT satellites. Root-mean-square (RMS) scatters at the centimeter level on the latitude and vertical components were achieved,
but 2-cm RMS scatters affected the longitude component. Nevertheless, results of relative velocity (123 mm/year N250°) are
very consistent with those obtained using the global positioning system (GPS) (126 mm/yr N246°). The co-seismic step (12 mm
N60°) related to the Walpole event (M
W = 7.7) is consistent with that derived from GPS (10 mm N30°) or from the centroid moment tensor (CMT) of the quake (12 mm
N000°).
Received: 19 November 1999 / Accepted: 17 May 2000 相似文献