By Shahrizal Ide Moslin. Researcher Malaysian Space Agency (MYSA) (shahrizal@mysa.gov.my) and Ooi Wei Han Researcher Malaysian Space Agency (MYSA) (ooiweihan@mysa.gov.my)
GNSS and its limitation
Global Navigation Satellite Systems (GNSS), or what we know more as GPS, BeiDou, Galileo and GLONASS technologies, are now ubiquitous in daily life. They have transformed navigation, being incorporated into electronic devices and are regularly utilised by the general public, the military and geoscientists. In developing nations, GNSS applications provide cost-effective solutions that make it possible to foster economic and social development while preserving the environment, thereby encouraging sustainable development.
Despite its widespread use, GNSS is not without its limitations. Atmospheric delays, satellite clock inaccuracies, and orbital deviations can lead to diminished positioning accuracy, sometimes by several metres. While basic GNSS is adequate for everyday applications such as smartphone navigation, it lacks the precision and reliability required for critical operations like aircraft navigation, where safety is paramount and such errors are unacceptable. Similarly, other applications like autonomous vehicle operation and precision agriculture, also require high accuracy. This is where space and ground-based augmentation systems like SBAS come into play, monitoring and correcting these errors to ensure the accuracy necessary for these crucial operations.
But how did SBAS come into existence? Why was it necessary, and what is new in SBAS technology? Let us explore.
The Need for Augmentation
Satellite-Based Augmentation System, also known as SBAS, is a wide-area differential GNSS augmentation system that uses geostationary satellites to broadcast primary GNSS data that have been enhanced by integrity and correction information provided by a network of ground stations covering large areas. The system offers real-time corrections to improve GNSS accuracy from approximately 10 metres to 1-2 metres, or even better in some instances. Furthermore, SBAS introduces essential integrity monitoring capabilities in the aviation sector that immediately notify pilots when GNSS signals become unreliable, thereby addressing critical safety concerns.
Today, the United Sates’ Wide Area Augmentation System (WAAS), European Geostationary Navigation Overlay Service (EGNOS), Japanese Multi-functional Satellite Augmentation System (MSAS) and Indian GPS Aided GEO Augmented Navigation (GAGAN) are among the major SBAS systems that are performing vital and expanding roles in variety of fields, including aviation, transportation, maritime, agriculture, emergency services, engineering, spatial and mapping, mining and more.
The History of SBAS: Early Developments (1990s – 2000s)
Before SBAS was accessible, pilots were obliged to depend solely on Instrument Landing Systems (ILS), which necessitated installing and maintaining costly ground-based infrastructure at each airport. The aviation authorities acknowledged these constraints and developed SBAS as a more advanced solution to simultaneously overcome various challenges.
The WAAS, which was introduced in 2003, was the inception of SBAS by the U.S. Federal Aviation Administration (FAA). WAAS’s initial obstacles included signal delays, limited coverage and certification issues. But by the late 2000s, it had become a game-changer for aviation, allowing for Category I (CAT-I) precision approaches without using ground-based ILS.
Worldwide Expansion of SBAS Networks
Following the success of WAAS, other regions implemented their own SBAS, such as:
EGNOS (2009) in Europe, facilitates maritime and aviation navigation;
MSAS (2007) in Japan, improves GPS signals throughout the Asia-Pacific region;
GAGAN (2015) in India, enables aviation and farming in rural regions.
SBAS has emerged as a global standard in the 2010s, having been acknowledged by the International Civil Aviation Organisation (ICAO) for safety-critical operations. This recognition, along with numerous countries also acknowledging the importance of this system, underscores the global impact of SBAS. It is a testament to the collaborative efforts and shared vision of professionals and researchers in navigation, aviation, agriculture and technology.
The SBAS landscape is expanding with the development of new regional systems globally. The forthcoming KASS system in South Korea is expected to improve GPS signal precision throughout East Asia, especially for aviation and maritime uses. Simultaneously, Africa’s ambitious ASECNA SBAS initiative seeks to transform air traffic safety and navigation proficiency throughout the continent’s challenging airspace. The SouthPAN is a joint collaboration between the Australian and New Zealand governments that offers SBAS services in the Southern Hemisphere, with a goal of achieving Full Operational Capability (FOC) by 2028. It is expected to benefit all satellite positioning users, particularly those in regional and remote areas without mobile phone coverage.
The expanding networks illustrate SBAS’s role as essential infrastructure for global positioning, with an increasing number of countries acknowledging its capacity to enhance economic productivity and transportation safety.
How Does SBAS Work?
SBAS enhances GNSS accuracy via a straightforward three-step procedure. A network of ground-based reference stations continuously monitors signals from navigation satellites, detecting any errors in the data. These measurements are transmitted to master control centres, where advanced computers analyse the data and compute accurate correction factors. These corrections are then relayed to geostationary satellites that disseminate them over extensive regions, enabling GNSS receivers to modify their positioning in real-time for much greater accuracy. This system operates constantly to deliver more dependable location data to users in aviation, maritime and other essential applications.
Expanding Applications of SBAS
Initially developed to satisfy aviation’s rigorous safety standards, SBAS technology has been extensively embraced across various sectors. In agriculture, farmers utilise their centimetre-level accuracy to guide automated tractors and optimise crop monitoring via precision farming methods. The autonomous vehicle industry increasingly depends on SBAS for the safe navigation of driverless cars and delivery drones operating without human oversight. Maritime operators employ SBAS-enhanced positioning for optimised ship routing and harbour navigation. At the same time, surveyors and construction teams attain exceptional accuracy in land mapping and infrastructure projects due to these advanced correction signals.
The Future of SBAS
SBAS is evolving rapidly, with exciting possibilities:
Integration with LEO Satellites: Low Earth Orbit (LEO) networks may improve SBAS coverage and reduce latency.
AI-Enhanced Corrections: Machine learning may predict and fix GNSS errors more efficiently.
Urban Air Mobility (UAM): SBAS will be essential for drone taxis and air traffic management in cities.
Malaysia and SBAS
Malaysia can utilise advanced SBAS technology to promote both technological advancement and economic growth across various sectors.
The system’s high-precision positioning capabilities enhance sectoral impact by facilitating accurate operations, including asset tracking, surveying and safety management, resulting in improved operational efficiency. In transportation, SBAS facilitates the advancement of autonomous vehicles and drone delivery systems while improving safety and efficiency in aviation and maritime operations.
Economically, SBAS promotes innovation and technological advancement in the GNSS sector, fostering expertise and capabilities in satellite navigation technologies. The infrastructure will facilitate the adoption of Industry 4.0, enhancing manufacturing and logistics competitiveness while creating high-value employment opportunities in the emerging satellite navigation sector.
The Future is Accurate and Reliable
SBAS technology has attained a mature phase, with multiple operational systems in place globally and others under development at different stages. With technological advancements, SBAS will assume an increasingly significant role in smart transportation, space navigation and beyond. Furthermore, there is a growing availability of commercial-off-the-shelf (COTS) products from reputable system-level companies with a track record in SBAS-related areas.
The future of SBAS enhancements is promising, offering the prospect of expanded applications. Many successful SBAS projects have notably adopted a regional or continental scale, allowing for cost-sharing to alleviate individual expenses related to system development and operation. Utilising a broader reference monitoring network also enhances system performance
