Countering GNSS high Accuracy applications Limitations due to Ionospheric disturbances in Brazil
Background & Objectives
GNSS supports applications where high accuracy is required, such as in precision agriculture, surveying, land management and off-shore operations. Relevant GNSS techniques are especially sensitive to ionospheric perturbations occurring in Brazil with the rise of the solar cycle, due to its location in one of the most affected regions of the Earth. CALIBRA will advance current algorithms to mitigate the effects of these perturbations and implement them in state of the art GNSS receivers.
Why this project is important for EGNOS/GSA/SatNav?
CALIBRA will counter the effects of Brazil’s disturbed ionosphere on GNSS, representing a positive blueprint for implementation at SBAS level, consequently leveraging the use of EGNOS in Brazil.
CALIBRA aims to study and devise commercially applicable solutions to mitigate the impact of ionospheric disturbances on high accuracy GNSS positioning techniques. Such techniques support an increasing range of operations requiring accuracy better than 10cm, which are particularly badly affected in Brazil due to the country’s geographical location across the magnetic equator. CALIBRA builds on the outcome of the CIGALA project, which led to solutions for improving signal tracking performance under ionospheric disturbances. Taking advantage of this head-start, CALIBRA’s objectives are to:
- Identify and describe vulnerabilities of GNSS carrier phase based techniques and reliant services/applications to ionospheric disturbances;
- Establish metric and characterise ionosphere related effects that degrade applications supported by GNSS techniques – RTK, NRTK and PPP in particular, in terms of accuracy, integrity and availability;
- Develop local empirical models for ionospheric TEC (Total Electron Content) climatology and scintillation that can assist the development of new algorithms for a ‘cleaner’ observable in order to enable improved positioning performance;
- Implement these algorithms on Septentrio’s state of the art multi-frequency multi-GNSS receivers;
- Carry out application specific field tests to validate and fine tune these algorithms.
How does it work?
In order to develop mitigation algorithms for GNSS carrier phase observables and implement them in GNSS receivers, CALIBRA will identify how these observables and existing algorithms are degraded by ionospheric phenomena, in terms of accuracy, integrity and availability. Using experimental evidence it will develop suitable countermeasures by building on expertise gathered by partners in this field through related projects and by exploiting data from established GNSS networks in Brazil.
CALIBRA will put in place a strategy involving research and industrial expertise to underpin user requirements for GNSS technology and build awareness of Galileo in a strategic market.
Work performed & results
- Characterise ionosphere driven shortcomings affecting RTK, PPP and related high accuracy GNSS techniques in Brazil through a multi-frequency multi GNSS perspective, addressing typical low latitude ionospheric disturbances, such as scintillation and strong TEC variations;
- Describe, assess and model the geophysical conditions causing these shortcomings, through continuous monitoring of the ionosphere from existing RTK networks and the CIGALA network;
- Develop novel and improved algorithms to counter these shortcomings through direct alignment with application driven requirements;
- Prototype and implement these algorithms in the CIGALA network receivers;
- Develop improved prototype RTK network software;
- Update Septentrio’s general RTK and PPP receivers’ firmware based on successful field testing/validation of the technical advancements resulting from the above.