共查询到20条相似文献，搜索用时 687 毫秒
1.
Partial integer decorrelation: optimum trade-off between variance reduction and bias amplification 总被引：2，自引：2，他引：0
Different techniques have been developed for determining carrier phase ambiguities, ranging from float approximations to the
efficient solution of the integer least square problem by the LAMBDA method. The focus so far was on double-differenced measurements.
Practical implementations of the LAMBDA method lead to a residual probability of wrong fixing of the order one percent. For
safety critical applications, this probability had to be reduced by eight orders of magnitude, which could be achieved by
linear multi-frequency code–carrier combinations. Scenarios with single or no differences include biases due to orbit errors,
satellite clock offsets, as well as residual code and phase biases. For this case, a linear combination of Galileo E1 and
E5 code and carrier phase measurements with a wavelength of 3.285 m and a noise level of a few centimeters is derived. This
ionosphere-free combination preserves the orbit and clock errors, and suppresses the E1 code multipath by 12.6 dB. Since integer
decorrelation transformations, as used in the LAMBDA method, inflate biases, the number of such transformations must be limited,
and applied in a judicious order. With a Galileo type constellation, this leads to a vertical standard deviation of ca. 20 cm,
while keeping the probability of wrong fixing extremely low for code biases of 10 cm, and phase biases of 0.1 cycle, combined
in a worst case. 相似文献
2.
Single receiver phase ambiguity resolution with GPS data 总被引：26，自引：12，他引：14
Willy Bertiger Shailen D. Desai Bruce Haines Nate Harvey Angelyn W. Moore Susan Owen Jan P. Weiss 《Journal of Geodesy》2010,84(5):327-337
Global positioning system (GPS) data processing algorithms typically improve positioning solution accuracy by fixing double-differenced
phase bias ambiguities to integer values. These “double-difference ambiguity resolution” methods usually invoke linear combinations
of GPS carrier phase bias estimates from pairs of transmitters and pairs of receivers, and traditionally require simultaneous
measurements from at least two receivers. However, many GPS users point position a single local receiver, based on publicly
available solutions for GPS orbits and clocks. These users cannot form double differences. We present an ambiguity resolution
algorithm that improves solution accuracy for single receiver point-positioning users. The algorithm processes dual- frequency
GPS data from a single receiver together with wide-lane and phase bias estimates from the global network of GPS receivers
that were used to generate the orbit and clock solutions for the GPS satellites. We constrain (rather than fix) linear combinations
of local phase biases to improve compatibility with global phase bias estimates. For this precise point positioning, no other
receiver data are required. When tested, our algorithm significantly improved repeatability of daily estimates of ground receiver
positions, most notably in the east component by approximately 30% with respect to the nominal case wherein the carrier biases
are estimated as real values. In this “static” test for terrestrial receiver positions, we achieved daily repeatability of
1.9, 2.1 and 6.0 mm in the east, north and vertical (ENV) components, respectively. For kinematic solutions, ENV repeatability
is 7.7, 8.4, and 11.7 mm, respectively, representing improvements of 22, 8, and 14% with respect to the nominal. Results from
precise orbit determination of the twin GRACE satellites demonstrated that the inter-satellite baseline accuracy improved
by a factor of three, from 6 to 2 mm up to a long-term bias. Jason-2/Ocean Surface Topography Mission precise orbit determination
tests results implied radial orbit accuracy significantly below the 10 mm level. Stability of time transfer, in low-Earth
orbit, improved from 40 to 7 ps. We produced these results by applying this algorithm within the Jet Propulsion Laboratory’s
(JPL’s) GIPSY/OASIS software package and using JPL’s orbit and clock products for the GPS constellation. These products now
include a record of the wide-lane and phase bias estimates from the underlying global network of GPS stations. This implies
that all GIPSY–OASIS positioning users can now benefit from this capability to perform single-receiver ambiguity resolution. 相似文献
3.
Oliver Montenbruck Miquel Garcia-Fernandez Yoke Yoon Steffen Schön Adrian Jäggi 《GPS Solutions》2009,13(1):23-34
Phase center variations of the receiver and transmitter antenna constitute a remaining uncertainty in the high precision orbit
determination (POD) of low Earth orbit (LEO) satellites using GPS measurements. Triggered by the adoption of absolute phase
patterns in the IGS processing standards, a calibration of the Sensor Systems S67-1575-14 antenna with GFZ choke ring has
been conducted that serves as POD antenna on various geodetic satellites such as CHAMP, GRACE and TerraSAR-X. Nominal phase
patterns have been obtained with a robotic measurement system in a field campaign and the results were used to assess the
impact of receiver antenna phase patterns on the achievable positioning accuracy. Along with this, phase center distortions
in the actual spacecraft environment were characterized based on POD carrier phase residuals for the GRACE and TerraSAR-X
missions. It is shown that the combined ground and in-flight calibration can improve the carrier phase modeling accuracy to
a level of 4 mm which is close to the pure receiver noise. A 3.5 cm (3D rms) consistency of kinematic and reduced dynamic
orbit determination solutions is achieved for TerraSAR-X, which presumably reflects the limitations of presently available
GPS ephemeris products. The reduced dynamic solutions themselves match the observations of high grade satellite laser ranging
stations to 1.5 cm but are potentially affected by cross-track biases at the cm-level. With respect to the GPS based relative
navigation of TerraSAR-X/TanDEM-X formation, the in-flight calibration of the antenna phase patterns is considered essential
for an accurate modeling of differential carrier phase measurements and a mm level baseline reconstruction.
相似文献
| Oliver MontenbruckEmail: |
4.
Jean-François Crétaux Stephane Calmant Vladimir Romanovski Anton Shabunin Florent Lyard Muriel Bergé-Nguyen Anny Cazenave Fabrice Hernandez Felix Perosanz 《Journal of Geodesy》2009,83(8):723-735
Altimetry missions such as Topex/Poseidon, Jason-1, GFO and ENVISAT have been widely used in the continental domain over lakes,
rivers and wetland although they were mostly dedicated to oceanic studies. Knowledge of the instrumental biases is a key issue.
Numerous sites have been dedicated to calibration purposes, either in the oceanic domain (Harvest offshore platform in California,
Corsica, Bass Strait in Australia) or over lakes (Lake Erie in United States). A new site (Lake Issykkul in Kirghizstan) is
proposed for calibration in the continental domain. This lake is covered by past (T/P) and current radar altimetry satellites
(Jason-1, T/P, GFO, and ENVISAT). Several in situ water levels and local meteorological variables are available at the site.
Located in a mountainous area, it offers an opportunity for calibration far away from all other existing sites and very different
environment contexts. Two GPS campaigns have been conducted on the lake in 2004 and in 2005. They consisted of cruises with
stations installed onboard a boat following the satellite ground tracks, and onshore settings. This enabled estimating a bias
for each altimeter and each tracking algorithm available. Biases obtained for Envisat, GFO, T/P and Jason-1 using the default
ocean tracker (respectively, 48.1 ± 6.6, 7.5 ± 4.0, 0 ± 4.3 and 7.0 ± 5.5 cm) agree with biases published at the other calibration
sites. For Jason-1, there is a significant disagreement with results obtained in the ocean field (7 cm instead of 13 cm) but
is coherent with bias obtained on the Lake Erie site. Erroneous estimates of the sea state bias correction from non-oceanic-like
waveforms is discussed as a possible explanation. Errors in the ionospheric, wet and dry tropospheric corrections for the
continental domain are also highlighted and quantified. 相似文献
5.
We examine the electromagnetic coupling of a GPS antenna–monument pair in terms of its simulated affect on long GPS coordinate
time series. We focus on the Earth and Polar Observing System (POLENET) monument design widely deployed in Antarctica and
Greenland in projects interested particularly in vertical velocities. We base our tests on an absolute robot calibration that
included the top ~0.15 m of the monument and use simulations to assess its effect on site coordinate time series at eight
representative POLENET sites in Antarctica over the period 2000.0–2011.0. We show that the neglect of this calibration would
introduce mean coordinate bias, and most importantly for velocity estimation, coordinate noise which is highly sensitive to
observation geometry and hence site location and observation period. Considering only sub-periods longer than 2.5 years, we
show vertical site velocities may be biased by up to ±0.4 mm/year, and biases up to 0.2 mm/year may persist for observation
spans of 8 years. Changing between uniform and elevation-dependent observation weighting alters the time series but does not
remove the velocity biases, nor does ambiguity fixing. The effect on the horizontal coordinates is negligible. The ambiguities
fixed series spectra show noise between flicker and random walk with near-white noise at the highest frequencies, with mean
spectral indices (frequencies <20 cycles per year) of approximately −1.3 (uniform weighting) and −1.4 (elevation-dependent
weighting). While the results are likely highly monument specific, they highlight the importance of accounting for monument
effects when analysing vertical coordinate time series and velocities for the highest precision and accuracy geophysical studies. 相似文献
6.
北斗天线电气相位中心偏差检验试验研究 总被引：1，自引：0，他引：1
为满足北斗双星定位系统精密定位、定向的工程需要,提出一种北斗天线电气相位中心常值偏差3维检验方法,并建立了相应的数学模型.该方法通过基线旋转、单天线旋转、交换天线,利用载波相位单差、基线长度、天线高差测量信息来估计天线电气相位中心偏差,并且在单天线旋转条件下对不同方向、不同天线间单差观测方程求差,以减少未知参数个数.最后,应用此模型检验一对北斗天线,检验结果表明,在单差均方差为0.005周,基线长度、天线间高差均方差为1 mm的条件下,天线间电气相位中心偏差水平分量的检验精度达0.3 mm.论文所述方法操作简单,适合在野外对北斗天线进行电气相位中心偏差检验. 相似文献
7.
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
8.
A preliminary study was conducted to evaluate the amount of pseudorange multipath at 390+ sites in the National Continuously Operating Reference Station (CORS) Network. The National CORS Network is a cooperative effort involving over 110 different agencies, universities, and private companies who seek to make GPS data from dual-frequency receivers located throughout the United States and its territories available to the general public. For CORS users, pseudorange multipath can seriously degrade the accuracy of any application that relies on precise measurements of the pseudorange observable over a short period of time, including differential pseudorange navigation, kinematic and rapid-static surveying, and ionospheric monitoring. The main objectives of this study were to identify the most affected and least affected sites in the network, to closely investigate problematic sites, and to compare various receiver/antenna combinations. Dual-frequency carrier phase and pseudorange measurements were used to estimate the amount of L1 and L2 pseudorange multipath at each site over a one-year period. Some of the most severely affected sites were maritime Differential GPS and Nationwide Differential GPS (DGPS/NDGPS) sites. Photographs obtained for these sites verified the presence of transmission towers and other reflectors in close proximity to the GPS antennas. Plotting the variations of the L1 and L2 pseudorange multipath with respect to azimuth and elevation further verified that even above a 60° elevation angle there was still as much as five meters of pseudorange multipath at some sites. The least affected sites were the state networks installed in Ohio and Michigan; these sites used excellent antenna mounts, choke ring antennas, and new receiver technology. A comparison of the 12 most commonly used receiver/antenna combinations in the CORS Network indicated that newer receivers such as the Ashtech UZ-12, Leica RS-500, and Trimble 5700 help to significantly mitigate pseudorange multipath, while the receivers/antennas at some DGPS/NDGPS sites, and the antennas formerly used at the Wide Area Augmentation System (WAAS) sites, are among those most affected by pseudorange multipath. The receiver/antenna comparison did not take into account the potential presence of reflectors at the sites (i.e., it is possible that a well-performing receiver/antenna combination could have been consistently placed at very poor site locations, and vice-versa).Product Disclaimer: Mention of a commercial company or product does not constitute an endorsement by the National Oceanic and Atmospheric Administration. Use for publicity or advertisement purposes of information from this paper concerning proprietary products or the comparison of such products is not authorized. 相似文献
9.
Vehicles such as passing trains produce significant short-term biases in coordinates of nearby GPS stations, preventing these coordinates from being used for structural monitoring of bridges. In order to study this problem, we carried out experiments with receivers recording at 100 Hz and located on both sides of a rail next to passing trains. The experiments focused on trains with similar characteristics and velocity. The analysis of the data revealed a short-duration bias in coordinates with amplitude up to 10 cm and high spectral frequencies. This bias is not due to wrong integer ambiguity fixing, software defects, and changing geometry of satellites and it does not significantly improve with the addition of GLONASS satellites. It is partly due to temporary blocking of certain satellites by passing vehicles and a dynamic multipath due to fast-moving, near-field reflective surfaces. This dynamic multipath seems to depend on the geometry of satellites and to be characterized by a shift of coordinates during the whole interval of the vehicle passage, as well as by very short-period coordinate fluctuations which are related to specific morphological characteristics of the train reflective surfaces. The amplitude of the dynamic multipath is smaller in the horizontal coordinates, which are also characterized by a clearer pattern than the vertical coordinates. On the basis of the above results, certain strategies for the modeling of the dynamic multipath are proposed. 相似文献
10.
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
11.
LIU Jiyu CHEN Xiaoming 《地球空间信息科学学报》2000,3(1):50-56
l lntroductionIn the winter Of l989 Wuhan Technical Universi-ty of Surveying and Mapping COntracted withTrimble Navigation Ltd. to purchase fOur TrimbIe4000SST receivers. They were required tO suit theaeriaI phWetric work without intreducing avelocity limitation. In February, l993 twO of thereceivers were uPgraded to provide two eventrnarker plugfords and one pulse Per second(lPPS) output axkets. The uPgradd receivers canincormrate external event markers, e. g. the shutter.oPening … 相似文献
12.
比较了IGS发布的相对天线相位中心改正模型与绝对天线相位中心改正模型,分析了两种不同模型对精密单点定位（PPP）参数估计的影响。结果表明,采用不同的天线相位中心改正模型,天顶对流层延迟（ZPD）的估值存在5mm左右的差异,接收机钟差参数存在3ns左右的差异,估计的测站坐标高程方向有1cm左右的差异。使用绝对天线相位中心模型估计得到的ZPD精度优于5mm,高程方向定位精度约为1cm,接收机钟差估计的精度达0.1ns。 相似文献
13.
Results of the estimation of azimuth-dependent phase center variations (PCVs) of GPS satellite antennas using global GPS data
are presented. Significant variations of up to ±3–4 mm that are demonstrated show excellent repeatability over eight years.
The application of the azimuthal PCVs besides the nadir-dependent ones will lead to a further reduction in systematic antenna
effects. In addition, the paper focuses on the benefit of a possible transition from relative to absolute PCVs. Apart from
systematic changes in the global station coordinates, one can expect the GPS results to be less dependent on the elevation
cut-off angle. This, together with the significant reduction of tropospheric zenith delay biases between GPS and VLBI, stands
for an important step toward more consistency between different space geodetic techniques. 相似文献
14.
Michael Moore Christopher Watson Matt King Simon McClusky Paul Tregoning 《Journal of Geodesy》2014,88(9):887-900
Continuous global positioning system (GPS) stations propagate biases and spurious signals into the derived parameter time series when the measurements are subject to site-specific effects, such as multipath. This is a particular problem in the investigation of geophysical and atmospheric phenomena where signals may be small in magnitude. A methodology to remove these erroneous signals from long-term time series will significantly increase the usefulness of the derived time series. This work provides the theoretical basis for use of an empirical site model (ESM) derived from post-fit phase residuals to mitigate unmodelled site-specific errors. Additionally, we also investigate the effectiveness of applying an ESM to a regional GPS network and a short baseline solution. Under most observing scenarios, we show that the ESM approach is predicted to improve the precision and accuracy of the site coordinates. However, it is important to note that we found some scenarios where the ESM can introduce a bias. For instance, when the antenna is mounted close to the ground. In this scenario, for a short baseline, we observed the introduction of a 4-mm bias in height. Use of an ESM for the same short baseline with an uncalibrated radome substantially improves the results by removing a large bias of over 10 mm in height. Similarly, application of an ESM derived from historic data yields similar improvements. This demonstrates that the ESM can be a powerful tool when applied to appropriate site-specific configurations and could potentially be implemented in routine GPS analysis for a broad range of applications. 相似文献
15.
16.
Daniela Thaller Rolf Dach Manuela Seitz Gerhard Beutler Maria Mareyen Bernd Richter 《Journal of Geodesy》2011,85(5):257-272
Satellite Laser Ranging (SLR) observations to Global Navigation Satellite System (GNSS) satellites may be used for several
purposes. On one hand, the range measurement may be used as an independent validation for satellite orbits derived solely
from GNSS microwave observations. On the other hand, both observation types may be analyzed together to generate a combined
orbit. The latter procedure implies that one common set of orbit parameters is estimated from GNSS and SLR data. We performed
such a combined processing of GNSS and SLR using the data of the year 2008. During this period, two GPS and four GLONASS satellites
could be used as satellite co-locations. We focus on the general procedure for this type of combined processing and the impact
on the terrestrial reference frame (including scale and geocenter), the GNSS satellite antenna offsets (SAO) and the SLR range
biases. We show that the combination using only satellite co-locations as connection between GNSS and SLR is possible and
allows the estimation of SLR station coordinates at the level of 1–2 cm. The SLR observations to GNSS satellites provide the
scale allowing the estimation of GNSS SAO without relying on the scale of any a priori terrestrial reference frame. We show
that the necessity to estimate SLR range biases does not prohibit the estimation of GNSS SAO. A good distribution of SLR observations
allows a common estimation of the two parameter types. The estimated corrections for the GNSS SAO are 119 mm and −13 mm on
average for the GPS and GLONASS satellites, respectively. The resulting SLR range biases suggest that it might be sufficient
to estimate one parameter per station representing a range bias common to all GNSS satellites. The estimated biases are in
the range of a few centimeters up to 5 cm. Scale differences of 0.9 ppb are seen between GNSS and SLR. 相似文献
17.
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
18.
Multipath is one of the most important error sources in Global Navigation Satellite System (GNSS) carrier-phase-based precise
relative positioning. Its theoretical maximum is a quarter of the carrier wavelength (about 4.8 cm for the Global Positioning
System (GPS) L1 carrier) and, although it rarely reaches this size, it must clearly be mitigated if millimetre-accuracy positioning
is to be achieved. In most static applications, this may be accomplished by averaging over a sufficiently long period of observation,
but in kinematic applications, a modelling approach must be used. This paper is concerned with one such approach: the use
of ray-tracing to reconstruct the error and therefore remove it. In order to apply such an approach, it is necessary to have
a detailed understanding of the signal transmitted from the satellite, the reflection process, the antenna characteristics
and the way that the reflected and direct signal are processed within the receiver. This paper reviews all of these and introduces
a formal ray-tracing method for multipath estimation based on precise knowledge of the satellite–reflector–antenna geometry
and of the reflector material and antenna characteristics. It is validated experimentally using GPS signals reflected from
metal, water and a brick building, and is shown to be able to model most of the main multipath characteristics. The method
will have important practical applications for correcting for multipath in well-constrained environments (such as at base
stations for local area GPS networks, at International GNSS Service (IGS) reference stations, and on spacecraft), and it can
be used to simulate realistic multipath errors for various performance analyses in high-precision positioning. 相似文献
19.
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
20.
GLONASS processing from mixed receiver types is typically subject to unmodeled inter-frequency phase biases which prevent carrier phase ambiguity parameters from converging to integers. Receiver-dependent values have been proposed to mitigate the contribution of these biases, but are still subject to a number of issues, such as firmware updates. Recent studies have demonstrated that the origin of inter-frequency biases is a misalignment between phase and code observations, and could be calibrated to first order by manufacturers. In this contribution, a calibration-free method for GLONASS ambiguity resolution is presented in which ambiguities naturally converge to integers. A mandatory condition is that two GLONASS satellites with adjacent frequency numbers are observed simultaneously, although this condition can be relaxed once a fixed solution has been obtained. This approach then permits the integration of different receiver types and firmware versions into seamless processing. 相似文献