Application of ionospheric tomography to real-time GPS carrier-phase ambiguities Resolution, at scales of 400-1000 km and with high geomagnetic activity

This paper proposes a model for combined Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) Real-Time Kinematic (RTK) positioning. The approach uses only one common reference ambiguity, for example, that of GPS L1, and estimates the pseudo-range and carrier phase system and frequency biases. The validations show that these biases are stable during a continuous reference ambiguity period and can be easily estimated, and the other estimated double-differenced ambiguities, such as those of GPS L2, BDS L1, and BDS L2, are not affected. Therefore, our approach solves the problems of a frequently changing reference satellite. In addition, because all the carrier phase observations use the same reference ambiguity, a relationship is established between the different systems and frequencies, and the strength of the combined model is thus increased.

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Recent Developments in Precise Point Positioning

GEOMATICA ◽

10.5623/cig2012-023 ◽

2012 ◽

Vol 66 (2) ◽

pp. 103-111 ◽

Cited By ~ 13

Author(s):

S. Bisnath ◽

P. Collins

Keyword(s):

Real Time ◽

Ambiguity Resolution ◽

Carrier Phase ◽

Precise Point Positioning ◽

Solution Convergence ◽

Similar Information ◽

Recent Developments ◽

Significant Step ◽

Point Positioning ◽

New Processing

In standard Precise Point Positioning (PPP), the carrier phase ambiguities are estimated as real-valued constants, so that the carrier-phases can provide similar information as the pseudoranges. As a consequence, it can take tens of minutes to several hours for the ambiguities to converge to suitably precise values. Recently, new processing methods have been identified that permit the ambiguities to be estimated more appropriately as integer-valued constants, as they are in relative Real-Time Kinematic (RTK) positioning. Under these conditions, standard ambiguity resolution techniques can be applied to strengthen the PPP solution. The result can be a greatly reduced solution convergence and re-convergence period, representing a significant step toward improving the performance of PPP with respect to that of RTK processing. This paper describes the underlying principles of the method, why the enhancements work, and presents some results.

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Covariance Analysis of Real-Time Precise GPS Orbit Estimated from Double-Differenced Carrier Phase Observations

Remote Sensing ◽

10.3390/rs11192271 ◽

2019 ◽

Vol 11 (19) ◽

pp. 2271 ◽

Cited By ~ 1

Author(s):

Sunkyoung Yu ◽

Donguk Kim ◽

Junesol Song ◽

Changdon Kee

Keyword(s):

Fault Detection ◽

Real Time ◽

Global Positioning System ◽

Carrier Phase ◽

Satellite System ◽

Additional Parameter ◽

Global Positioning ◽

Correlation Information ◽

Global Navigation Satellite ◽

Orbit Errors

The covariance of real-time global positioning system (GPS) orbits has been drawing attention in various fields such as user integrity, navigation performance improvement, and fault detection. The international global navigation satellite system (GNSS) service (IGS) provides real-time orbit standard deviations without correlations between the axes. However, without correlation information, the provided covariance cannot assure the performance of the orbit product, which would, in turn, causes significant problems in fault detection and user integrity. Therefore, we studied real-time GPS orbit covariance characteristics along various coordinates to effectively provide conservative covariance. To this end, the covariance and precise orbits are estimated by means of an extended Kalman filter using double-differenced carrier phase observations of 61 IGS reference stations. Furthermore, we propose a new method for providing covariance to minimize loss of correlation. The method adopted by the IGS, which neglects correlation, requires 4.5 times the size of the covariance to bind orbit errors. By comparison, our proposed method reduces this size from 4.5 to 1.3 using only one additional parameter. In conclusion, the proposed method effectively provides covariance to users.

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Integrity Monitoring for Carrier Phase Ambiguities

Journal of Navigation ◽

10.1017/s037346331100052x ◽

2011 ◽

Vol 65 (1) ◽

pp. 41-58 ◽

Cited By ~ 17

Author(s):

Shaojun Feng ◽

Washington Ochieng ◽

Jaron Samson ◽

Michel Tossaint ◽

Manuel Hernandez-Pajares ◽

...

Keyword(s):

Least Squares ◽

Real Time ◽

Ambiguity Resolution ◽

Carrier Phase ◽

Integer Number ◽

Integrity Monitoring ◽

Level Of Confidence ◽

F Distribution ◽

Position Solution ◽

T Distribution

The determination of the correct integer number of carrier cycles (integer ambiguity) is the key to high accuracy positioning with carrier phase measurements from Global Navigation Satellite Systems (GNSS). There are a number of current methods for resolving ambiguities including the Least-squares AMBiguity Decorrelation Adjustment (LAMBDA) method, which is a combination of least-squares and a transformation to reduce the search space. The current techniques to determine the level of confidence (integrity) of the resolved ambiguities (i.e. ambiguity validation), usually involve the construction of test statistics, characterisation of their distribution and definition of thresholds. Example tests applied include ratio, F-distribution, t-distribution and Chi-square distribution. However, the assumptions that underpin these tests have weaknesses. These include the application of a fixed threshold for all scenarios, and therefore, not always able to provide an acceptable integrity level in the computed ambiguities. A relatively recent technique referred to as Integer Aperture (IA) based on the ratio test with a large number of simulated samples of float ambiguities requires significant computational resources. This precludes the application of IA in real time.This paper proposes and demonstrates the power of an integrity monitoring technique that is applied at the ambiguity resolution and positioning stages. The technique has the important benefit of facilitating early detection of any potential threat to the position solution, originating in the ambiguity space, while at the same time giving overall protection in the position domain based on the required navigation performance. The proposed method uses the conventional test statistic for ratio testing together with a doubly non-central F distribution to compute the level of confidence (integrity) of the ambiguities. Specifically, this is determined as a function of geometry and the ambiguity residuals from least squares based ambiguity resolution algorithms including LAMBDA. A numerical method is implemented to compute the level of confidence in real time.The results for Precise Point Positioning (PPP) with simulated and real data demonstrate the power and efficiency of the proposed method in monitoring both the integrity of the ambiguity computation and position solution processes. Furthermore, due to the fact that the method only requires information from least squares based ambiguity resolution algorithms, it is easily transferable to conventional Real Time Kinematic (RTK) positioning.

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Highly-accurate real-time syntonization by use of a single-frequency receiver with GPS carrier phase

18th European Frequency and Time Forum (EFTF 2004) ◽

10.1049/cp:20040841 ◽

2004 ◽

Cited By ~ 1

Author(s):

C.L. Cheng ◽

F.R. Chang ◽

L.S. Wang ◽

K.Y. Tu

Keyword(s):

Real Time ◽

Carrier Phase ◽

Single Frequency

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Real-Time GPS Clock Monitoring with IGS Ultra-Rapid Products

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.301-303.1293 ◽

2011 ◽

Vol 301-303 ◽

pp. 1293-1298

Author(s):

Youn Jeong Heo ◽

Jeongho Cho ◽

Moon Beom Heo

Keyword(s):

Real Time ◽

Carrier Phase ◽

Time Transfer ◽

Satellite Clock ◽

Short Term ◽

Transfer Method ◽

The Stability

The objective of this study is to develop a real-time strategy that results in higher precision than any real-time solutions currently available for GPS satellite clock monitoring. A real-time time transfer methodology was employed for satellite clock monitoring, composed of carrier phase smoothed code measurements and IGS ultra-rapid products to obtain precise satellite positions. The performance of the time transfer method was assessed by comparison with the results based on the all-in-view method using the broadcasting ephemeredes. The results showed that the stability of satellite clock monitoring for a short-term period was improved by the proposed method.

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The Multipath Influence in Real-Time Kinematic of GNSS Observations at Different Antenna Heights

EMITTER International Journal of Engineering Technology ◽

10.24003/emitter.v7i2.427 ◽

2019 ◽

Vol 7 (2) ◽

Author(s):

Bakheet Agab Nour ◽

Ahmet Turan Ozdemir ◽

Peter Garang ◽

Oğuzhan Ağırbaş

Keyword(s):

Signal Processing ◽

Real Time ◽

Carrier Phase ◽

Inverse Relationship ◽

Antenna Design ◽

Error Source ◽

Multipath Error ◽

Real Time Kinematic ◽

Gnss Observations

Multipath is a dominant error source in Real-Time Kinematic (RTK) applications that reduces the position, time and velocity accuracy. Mitigation of such errors can be achieved by better signal processing and antenna design. This paper attempts to examine the different height of RTK system antenna with regards to the multipath error. The results obtained in this work show height significantly change of multipath in pseudo range (MP1) and multipath in the carrier phase (MP2). Different antenna height does not give the same multipath error result in the tests that we have conducted in this work. The optimal height of the antenna was achieved as two meters in order to obtain a minimum multipath error for MP1 and MP2. At the end of this work, we experimentally proved that there is an inverse relationship between the height of the antenna and multipath with RTK algorithm.

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