Partial ambiguity resolution for reliable GNSS positioning — A useful tool?

2016 ◽  
Author(s):  
Andreas Brack
Keyword(s):  
Ambiguity Resolution ◽  
Partial Ambiguity Resolution ◽  
Gnss Positioning

scholarly journals Partial Carrier-Phase Integer Ambiguity Resolution for High Accuracy GNSS Positioning

2020 ◽  
Author(s):  
Andreas Brack
Keyword(s):  
Ambiguity Resolution ◽  
Carrier Phase ◽  
Real Data ◽  
Global Navigation Satellite Systems ◽  
Integer Ambiguity ◽  
Phase Measurements ◽  
Satellite Systems ◽  
Partial Ambiguity Resolution ◽  
Gnss Positioning ◽  
Global Navigation Satellite

Global navigation satellite systems provide ranging based positioning and timing services. The use of the periodic carrier-phase signals is the key to fast and accurate solutions, given that the inherent ambiguities of the carrier-phase measurements are correctly resolved. The idea of partial ambiguity resolution is to resolve a subset of all ambiguities, which enables faster solutions but does not fully exploit the high precision of the carrier-phase measurements. Theory, methods, and algorithms for partial ambiguity resolution are discussed and analyzed with simulated and real data.

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.

scholarly journals GLONASS FDMA data for RTK positioning: a five-system analysis

GPS Solutions ◽  
2020 ◽  
Vol 25 (1) ◽  
Author(s):  
Andreas Brack ◽  
Benjamin Männel ◽  
Harald Schuh
Keyword(s):  
Ambiguity Resolution ◽  
System Analysis ◽  
Formal Analysis ◽  
Real Data ◽  
Strong Impact ◽  
Combined Model ◽  
Partial Ambiguity Resolution ◽  
Long Baseline ◽  
Weighted Model ◽  
Difference Test

Abstract The use of the GLONASS legacy signals for real-time kinematic positioning is considered. Due to the FDMA multiplexing scheme, the conventional CDMA observation model has to be modified to restore the integer estimability of the ambiguities. This modification has a strong impact on positioning capabilities. In particular, the ambiguity resolution performance of this model is clearly weaker than for CDMA systems, so that fast and reliable full ambiguity resolution is usually not feasible for standalone GLONASS, and adding GLONASS data in a multi-GNSS approach can reduce the ambiguity resolution performance of the combined model. Partial ambiguity resolution was demonstrated to be a suitable tool to overcome this weakness (Teunissen in GPS Solut 23(4):100, 2019). We provide an exhaustive formal analysis of the positioning precision and ambiguity resolution capabilities for short, medium, and long baselines in a multi-GNSS environment with GPS, Galileo, BeiDou, QZSS, and GLONASS. Simulations are used to show that with a difference test-based partial ambiguity resolution method, adding GLONASS data improves the positioning performance in all considered cases. Real data from different baselines are used to verify these findings. When using all five available systems, instantaneous centimeter-level positioning is possible on an 88.5 km baseline with the ionosphere weighted model, and on average, only 3.27 epochs are required for a long baseline with the ionosphere float model, thereby enabling near instantaneous solutions.

scholarly journals Predicting the Success Rate of Long-baseline GPS+Galileo (Partial) Ambiguity Resolution

2014 ◽  
Vol 67 (3) ◽  
pp. 385-401 ◽  
Author(s):  
Dennis Odijk ◽  
Balwinder S. Arora ◽  
Peter J.G. Teunissen
Keyword(s):  
Ambiguity Resolution ◽  
Satellite System ◽  
Observation Time ◽  
Baseline Length ◽  
Success Rates ◽  
Dual Frequency ◽  
Variance Matrix ◽  
Partial Ambiguity Resolution ◽  
Long Baseline ◽  
Triple Frequency

This contribution covers precise (cm-level) relative Global Navigation Satellite System (GNSS) positioning for which the baseline length can reach up to a few hundred km. Carrier-phase ambiguity resolution is required to obtain this high positioning accuracy within manageable observation time spans. However, for such long baselines, the differential ionospheric delays hamper fast ambiguity resolution as based on current dual-frequency Global Positioning System (GPS). It is expected that the modernization of GPS towards a triple-frequency system, as well as the development of Galileo towards a full constellation will be beneficial in speeding up long-baseline ambiguity resolution. In this article we will predict ambiguity resolution success rates for GPS+Galileo for a 250 km baseline based on the ambiguity variance matrix, where the Galileo constellation is simulated by means of Yuma almanac data. From our studies it can be concluded that ambiguity resolution will likely become faster (less than ten minutes) in the case of GPS+Galileo when based on triple-frequency data of both systems, however much shorter times to fix the ambiguities (one-two minutes) can be expected when only a subset of ambiguities is fixed instead of the complete vector (partial ambiguity resolution).

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