Ambiguity Resolution in Carrier Phase Based Positioning Using Lambda Method

2019 ◽  
Author(s):  
Adnan Ashraf ◽  
Najam Abbas Naqvi ◽  
Zohaib Afzal
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Lambda Method

Ambiguity Resolution in ZigBee Phase Shift Measurements Using MAFA Method

2017 ◽  
Author(s):  
Jacek Rapinski ◽  
Slawomir Cellmer ◽  
Joanna Janicka
Keyword(s):  
Phase Shift ◽  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Standard Procedure ◽  
Wave Length ◽  
Functional Model ◽  
Single Wave ◽  
Satellite Positioning ◽  
Phase Data ◽  
Gnss Measurements

This paper presents ZigBee module that is used for ranging in indoor positioning. The system is using the phase shift measurements to determine the distances between user and anchors. The nature of phase shift measurements is causing the results to be in the range of a single wave length. Thus, as in GNSS measurements, appears the problem with ambiguity resolution. In satellite positioning this issue is well described but in range-based ZigBee positioning this problem needs to be solved. The standard procedure to find the correct values of ambiguities is to search for a combination of observation equations with smallest RMS. The authors propose a different solution – the Modified Ambiguity Function Approach (MAFA). It is a method of GNSS carrier phase data processing. In this method, the integer nature of ambiguities is taken into account in the functional model of the adjustment.

Recent Developments in Precise Point Positioning

GEOMATICA ◽  
2012 ◽  
Vol 66 (2) ◽  
pp. 103-111 ◽  
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.

scholarly journals Kinematic ME-MAFA for Pseudolite Carrier-Phase Ambiguity Resolution in Precise Single-Point Positioning

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6197
Author(s):  
Kai Liu ◽  
Xiye Guo ◽  
Jun Yang ◽  
Xiaoyu Li ◽  
Changshui Liu ◽  
...  
Keyword(s):  
Success Rate ◽  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Single Point ◽  
Heuristic Method ◽  
Voronoi Cell ◽  
Static Mode ◽  
Single Point Positioning ◽  
Cycle Slips ◽  
Point Positioning

Precise single-point positioning using carrier-phase measurements can be provided by the synchronized pseudolite system. The primary task of carrier phase positioning is ambiguity resolution (AR) with rapidity and reliability. As the pseudolite system is usually operated in the dense multipath environment, cycle slips may lead the conventional least-squares ambiguity decorrelation adjustment (LAMBDA) method to incorrect AR. A new AR method based on the idea of the modified ambiguity function approach (MAFA), which is insensitive to the cycle slips, is studied in this paper. To improve the model strength of the MAFA and to eliminate the influence of constant multipath biases on the time-average model in static mode, the kinematic multi-epoch MAFA (kinematic ME-MAFA) algorithm is proposed. A heuristic method for predicting the ‘float position’ corresponding to every Voronoi cell of the next epoch, making use of Doppler-based velocity information, is implemented to improve the computational efficiency. If the success rate is very close to 1, it is possible to guarantee reliable centimeter-level accuracy positioning without further ambiguity validation. Therefore, a computing method of the success rate for the kinematic ME-MAFA is proposed. Both the numerical simulations and the kinematic experiment demonstrate the feasibility of the new AR algorithm according to its accuracy and reliability. The accuracy of the horizontal positioning solution is better than 1.7 centimeters in our pseudolite system.

scholarly journals On-the-fly Ambiguity Resolution Using an Estimator of the Modified Ambiguity Covariance Matrix for the GNSS Positioning Model Based on Phase Data

2012 ◽  
Vol 47 (3) ◽  
pp. 81-90 ◽  
Author(s):  
S. Cellmer
Keyword(s):  
Covariance Matrix ◽  
Ambiguity Resolution ◽  
Positive Definiteness ◽  
Small Data ◽  
Data Set ◽  
Gnss Positioning ◽  
Model Based ◽  
Lambda Method ◽  
Phase Data ◽  
Single Epoch

On-the-fly Ambiguity Resolution Using an Estimator of the Modified Ambiguity Covariance Matrix for the GNSS Positioning Model Based on Phase Data On-the-fly ambiguity resolution (OTF AR) is based on a small data set, obtained from a very short observation session or even from a single epoch observation. In these cases, a classical approach to ambiguity resolution (e.g. the Lambda method) can meet some numerical problems. The basis of the Lambda method is an integer decorrelation of the positive definite ambiguity covariance matrix (ACM). The necessary condition for the proper performing of this procedure is a positive definiteness of ACM. However, this condition is not satisfied in cases of very short observation sessions or single epoch positioning if phase-only observations are used. The subject of this contribution is such a case where phase-only observations are used in the final part of the computational process. The modification of ACM is proposed in order to ensure its positive definiteness. An estimator of modified ACM is a good ACM approximation for the purpose of performing the LAMBDA method. Another problem of short sessions (or a single epoch) positioning is the poor quality of the float solution. In this paper, a cascade adjustment with wide-lane combinations of signals L1 and L2 as a method of solving this problem is presented.

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