scholarly journals On-The-Fly Ambiguity Resolution Based on Double-Differential Square Observation

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2495 ◽  
Author(s):  
Tengfei Wang ◽  
Zheng Yao ◽  
Mingquan Lu
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Base Stations ◽  
Navigation Systems ◽  
Phase Measurements ◽  
Positioning Systems ◽  
Key Factor ◽  
Fixed Solution ◽  
Geometric Changes ◽  
Global Navigation Systems

Global navigation systems provide worldwide positioning, navigation and navigation services. However, in some challenging environments, especially when the satellite is blocked, the performance of GNSS is seriously degraded or even unavailable. Ground based positioning systems, including pseudolites and Locata, have shown their potentials in centimeter-level positioning accuracy using carrier phase measurements. Ambiguity resolution (AR) is a key issue for such high precision positioning. Current methods for the ground based systems need code measurements for initialization and/or approximating linearization. If the code measurements show relatively large errors, current methods might suffer from convergence difficulties in ground based positioning. In this paper, the concept of double-differential square observation (DDS) is proposed, and an on-the-fly ambiguity resolution (OTF-AR) method is developed for ground based navigation systems using two-way measurements. An important advantage of the proposed method is that only the carrier phase measurements are used, and code measurements are not necessary. The clock error is canceled out by two-way measurements between the rover and the base stations. The squared observations are then differenced between different rover positions and different base stations, and a linear model is then obtained. The floating integer values are easy to compute via this model, and there is no need to do approximate linearization. In this procedure, the rover’s approximate coordinates are also directly obtained from the carrier measurements, therefore code measurements are not necessary. As an OTF-AR method, the proposed method relies on geometric changes caused by the rover’s motion. As shown by the simulations, the geometric diversity of observations is the key factor for the AR success rate. Moreover, the fine floating solutions given by our method also have a fairly good accuracy, which is valuable when fixed solutions are not reliable. A real experiment is conducted to validate the proposed method. The results show that the fixed solution could achieve centimeter-level accuracy.

Carrier Phase Relative RAIM Algorithms and Protection Level Derivation

2010 ◽  
Vol 63 (2) ◽  
pp. 215-231 ◽  
Author(s):  
Livio Gratton ◽  
Mathieu Joerger ◽  
Boris Pervan
Keyword(s):  
Fault Detection ◽  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Resolution Time ◽  
Protection Level ◽  
Integrity Monitoring ◽  
Phase Measurements ◽  
Aircraft Navigation ◽  
Time Differential ◽  
Receiver Autonomous Integrity Monitoring

The concept of Relative Receiver Autonomous Integrity Monitoring (RRAIM) using time differential carrier phase measurements is investigated in this paper. The precision of carrier phase measurements allows for mitigation of integrity hazards by implementing RRAIM monitors with tight thresholds without significantly affecting continuity. In order to avoid the need for cycle ambiguity resolution, time differences in carrier phase measurements are used as the basis for detection. In this work, we examine RRAIM within the context of the GNSS Evolutionary Architecture Study (GEAS), which explores potential architectures for aircraft navigation utilizing the satellite signals available in the mid-term future with GPS III. The objectives of the GEAS are focused on system implementations providing worldwide coverage to satisfy LPV-200 operations, and potentially beyond. In this work, we study two different GEAS implementations of RRAIM. General formulas are derived for positioning, fault detection, and protection level generation to meet a given set of integrity and continuity requirements.

scholarly journals Phase Ambiguity Resolution Method Using Processing of Code and Carrier Phase Pseudoranges in a Kalman-Type Filter

2021 ◽  
Vol 8 (3) ◽  
pp. 72-80
Author(s):  
V. E. Vovasov ◽  
◽  
R. B. Mazepa ◽  
D. A. Sukharev ◽  
A. V. Voropaeva ◽  
...  
Keyword(s):  
High Precision ◽  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Phase Ambiguity ◽  
Phase Measurements ◽  
Phase Ambiguity Resolution ◽  
Code Pseudorange ◽  
L1 And L2 ◽  
Base Network ◽  
Observation Period

The main problem of implementing high-precision pseudoranges by carrier phase lies in their ambiguity associated with the ambiguity of the phase measurements of the navigation receiver. Thus, the development of new methods for phase ambiguity resolution becomes a very important element of high-precision positioning. The paper considers relative methods for estimating the coordinates of a stationary object that involve the use of both user and base (network in the case of a network of base receivers) receivers with precisely known coordinates located at a distance of several thousand kilometers from each other. We propose an algorithm for phase ambiguity resolution (integer type) based on the use of a Kalman-type filter (KTF), which receives ionosphere-free combinations of code and carrier phase pseudoranges. It is shown that traditional methods of ambiguity resolution require a significant observation period (about 2,000 seconds). We propose a method for evaluating the linear combination of phase ambiguities in the L1 and L2 bands obtained from instantaneous phase measurements. Its application along with the estimation of KTF parameters makes it possible to resolve phase ambiguities from as early as 50 seconds of observation. Set forth are the results of an experiment, in which code pseudorange measurements are used prior to the resolution of phase ambiguities and carrier phase pseudorange measurements are used after ambiguity resolution.

scholarly journals Detecting Cycle Slips in Carrier-Phase Measurements of Single Frequency Navigation Receivers with Different Instabilities of Reference Oscillators

2021 ◽  
Vol 5 (2) ◽  
pp. 144-161
Author(s):  
A. S. Pustoshilov ◽  
◽  
S. P. Tsarev ◽  
Keyword(s):  
Carrier Phase ◽  
Single Frequency ◽  
Navigation Systems ◽  
Noise Component ◽  
Phase Measurements ◽  
Additional Information ◽  
Cycle Slips ◽  
Reference Oscillator ◽  
The Difference ◽  
Polynomial Filtering

The use of carrier-phase measurements significantly increases the accuracy of solutions when using the measurements of navigation receivers. One of the problems in carrier-phase measurements is discontinuities (cycle slips) in the measurements. The existing algorithms of detection and compensation of cycle slips in carrier-phase measurements of a singlefrequency navigation receiver either require additional information (for example, Doppler measurements), or operate only in differential mode, or can only detect large cycle slips. The purpose of the research is the development of algorithms for detecting small cycle slips in carrier-phase measurements of single-frequency receivers without using additional information. We use methods of filtering of the trend in the carrier-phase measurements using polynomial or adaptive bases, as well as modified sparse recovery algorithms to estimate cycle slips in the difference between code and carrier-phase measurements. The algorithm which is used to search cycle slips in carrier-phase measurements depends on the quality of the reference oscillator of the navigation receiver. For receivers with high-stability reference oscillators (e.g. active hydrogen maser), one can use polynomial filtering of the trend, the filtering result directly detects discontinuities in carrier-phase measurements with a probability close to unity. For navigation receivers with low-stability reference oscillators (quartz reference oscillators), a modified algorithm for minimization of the total variation with filtering of the trend applied to the difference between the code and carrier-phase single-frequency measurements detects discontinuities in 1 cycle slip against the background of the noise component of comparable magnitude with a probability of 0.8. The results may be applied in navigation systems with single-frequency receivers with low stability reference oscillators, as well as in a posteriori processing of receivers’ measurements to correct carrier-phase measurements on the preprocessing stage.

scholarly journals Indoor Carrier Phase Positioning Technology Based on OFDM System

Sensors ◽  
2021 ◽  
Vol 21 (20) ◽  
pp. 6731
Author(s):  
Zhenyu Zhang ◽  
Shaoli Kang ◽  
Xiang Zhang
Keyword(s):  
High Resolution ◽  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Phase Measurement ◽  
Research Direction ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Ofdm Systems ◽  
Carrier Phase Measurement ◽  
Phase Measurements

Carrier phase measurement is a ranging technique that uses the receiver to determine the phase difference between the received signal and the transmitted signal. Carrier phase ranging has a high resolution; thus, it is an important research direction for high precision positioning. It is widely used in global navigation satellite systems (GNSS) systems but is not yet commonly used inwireless orthogonal frequency division multiplex (OFDM) systems. Applying carrier phase technology to OFDM systems can significantly improve positioning accuracy. Like GNSS carrier phase positioning, using the OFDM carrier phase for positioning has the following two problems. First, multipath and non-line-of-sight (NLOS) propagation have severe effects on carrier phase measurements. Secondly, ambiguity resolution is also a primary issue in the carrier phase positioning. This paper presents a ranging scheme based on the carrier phase in a multipath environment. Moreover, an algorithm based on the extended Kalman filter (EKF) is developed for fast integer ambiguity resolution and NLOS error mitigation. The simulation results show that the EKF algorithm proposed in this paper solves the integer ambiguity quickly. Further, the high-resolution carrier phase measurements combined with the accurately estimated integer ambiguity lead to less than 30-centimeter positioning error for 90% of the terminals. In conclusion, the presented methods gain excellent performance, even when NLOS error occur.

scholarly journals RELIABILITY OF THE GPS CARRIER-PHASE FIX SOLUTION UNDER HARSH CONDITION

2022 ◽  
Vol XLVI-4/W3-2021 ◽  
pp. 223-227
Author(s):  
M. I. Mohd Dzukhi ◽  
T. A. Musa ◽  
W. A. Wan Aris ◽  
A. H. Omar ◽  
I. A. Musliman
Keyword(s):  
Carrier Phase ◽  
Estimation Procedure ◽  
Control Measures ◽  
Base Stations ◽  
Integer Ambiguity ◽  
Gps Positioning ◽  
Gps Observation ◽  
Ambiguity Validation ◽  
Fixed Solution ◽  
Harsh Condition

Abstract. Once the unknown integer ambiguity values are resolved, the GPS carrier phase observation will be transformed into a millimeter-level precision measurement. However, GPS observation are prone to a variety of errors, making it a biased measurement. There are two components in identifying integer ambiguities: estimation and validation. The estimation procedure aims to determine the ambiguity's integer values, and the validation step checks whether the estimated integer value is acceptable. Even though the theory and procedures for ambiguity estimates are well known, the topic of ambiguity validation is still being researched. The dependability of computed coordinates will be reduced if a false fixed solution emerges from an incorrectly estimated ambiguity integer value. In this study, the reliability of the fixed solution obtained by using several base stations in GPS positioning was investigated, and the coordinates received from these bases were compared. In a conclusion, quality control measures such as employing several base stations will improve the carrier phase measurement's accuracy.

scholarly journals Receiver Widelane Analysis and Its Effect on Precise Point Positioning

2014 ◽  
Vol XL-2 ◽  
pp. 133-136
Author(s):  
M. Elsobeiey
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Precise Point Positioning ◽  
The Other ◽  
Satellite Clock ◽  
Phase Measurements ◽  
Other Hand ◽  
Differential Methods ◽  
Point Positioning ◽  
Over Time

Typically, differential carrier-phase-based methods have been used in positioning applications that require high accuracy. The main advantage of differential methods is solving the carrier-phase ambiguities and obtain millimetre-level accuracy carrier-phase measurements. Recent studies showed that it is possible to fix the un-differenced carrier-phase ambiguities into integers which is well-known as un-differenced carrier-phase ambiguity resolution. Unfortunately, the IGS neglects satellite hardware delay during satellite clock corrections estimation process. In case of differential methods, however, this will not affect the user as all common errors between the reference and rover receivers will be cancelled out by. Point positioning, on the other hand, will be affected by neglecting satellite hardware delays as those hardware delays will be lumped into the carrier-phase ambiguities destroying its integer nature. To solve this problem, satellite clock corrections must be estimated based on clock correction for each observable bases. The user, on the other hand, can form the ionosphere-free linear combination and divide and fix its two components, namely widelane and narrowlane. If both ambiguities are successfully fixed, few millimetres level of accuracy measurements are then obtained. In this paper, one month (December, 2013) of GPS data is used to study the receiver widelane bias, its behaviour over time, and receiver dependency are provided. It is shown that the receiver widelane bias is receiver dependent, stable over time for high-grade geodetic receivers. These results are expected to have a great impact on precise point positioning (PPP) conversion time and PPP carrierphase ambiguity resolution.

scholarly journals Triple-Frequency GPS Precise Point Positioning Ambiguity Resolution Using Dual-Frequency Based IGS Precise Clock Products

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Fei Liu ◽  
Yang Gao
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Precise Point Positioning ◽  
Free Carrier ◽  
Convergence Time ◽  
Dual Frequency ◽  
Phase Measurements ◽  
Triple Frequency ◽  
Wide Lane ◽  
Point Positioning

With the availability of the third civil signal in the Global Positioning System, triple-frequency Precise Point Positioning ambiguity resolution methods have drawn increasing attention due to significantly reduced convergence time. However, the corresponding triple-frequency based precise clock products are not widely available and adopted by applications. Currently, most precise products are generated based on ionosphere-free combination of dual-frequency L1/L2 signals, which however are not consistent with the triple-frequency ionosphere-free carrier-phase measurements, resulting in inaccurate positioning and unstable float ambiguities. In this study, a GPS triple-frequency PPP ambiguity resolution method is developed using the widely used dual-frequency based clock products. In this method, the interfrequency clock biases between the triple-frequency and dual-frequency ionosphere-free carrier-phase measurements are first estimated and then applied to triple-frequency ionosphere-free carrier-phase measurements to obtain stable float ambiguities. After this, the wide-lane L2/L5 and wide-lane L1/L2 integer property of ambiguities are recovered by estimating the satellite fractional cycle biases. A test using a sparse network is conducted to verify the effectiveness of the method. The results show that the ambiguity resolution can be achieved in minutes even tens of seconds and the positioning accuracy is in decimeter level.

GPS MARINE KINEMATIC POSITIONING ACCURACY AND RELIABILITY

1987 ◽  
Vol 41 (2) ◽  
pp. 143-172 ◽  
Author(s):  
G. Lachapelle ◽  
M. Casey ◽  
R.M. Eaton ◽  
A. Kleusberg ◽  
J. Tranquilla ◽  
...  
Keyword(s):  
Carrier Phase ◽  
Point Of View ◽  
Navigation Systems ◽  
Inertial Navigation Systems ◽  
Error Sources ◽  
Positioning Accuracy ◽  
Phase Measurements ◽  
Marine Applications ◽  
The One ◽  
Two Parameters

Positioning accuracy and reliability are two parameters of major concern to GPS marine users. GPS limitations and error sources are analyzed from a user’s point of view. The coverage limitations inherent to the (18 + 3) satellite constellation are discussed and related outages inherent to specific geographical areas are described. Receiver and antenna characteristics are described in relation to their effect on positioning accuracy and reliability. Antenna requirements for shipborne applications are discussed. The effect of the troposphere and ionosphere on GPS measurements is quantified for various cases. Multipath and imaging effects on both P and CIA code and carrier phase measurements are discussed. A variety of user accuracy and reliability enhancements are described. These include the use of seven-channel receivers and that of height and time constraints to increase redundancy and limit poor geometry effects, the use of differential methods to reduce satellite and propagation medium errors, the integration of code and carrier phase measurements to increase positioning accuracy, and the use of external sensors such as pitch and roll sensors, and inertial navigation systems. It is concluded that GPS is capable of achieving the one metre accuracy level for marine applications provided that error sources specific to shipborne applications can be effectively controlled.

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