Functional augmentations of GNSS
The article explores satellite and ground-based augmentations to GNSS in aviation. It highlights their key features, advantages, and disadvantages. Their crucial role in enhancing the safety and efficiency of aviation navigation is emphasized
Functional augmentations
Reading time: ~12-15 minutes
In the previous article, we introduced the concept of area navigation in aviation. A further review and deep dive into the topic awaits us as part of the knowledge library we are preparing on the checkcrosscheck.space platform.
Area navigation is a method whereby an aircraft flies along a given path with a certain degree of accuracy. The main focus was on three primary types of area navigation: LNAV (lateral), VNAV (vertical), and 4D navigation, which includes a time parameter. Key conditions for successful flight using this technology were also outlined.
Area navigation is a method whereby an aircraft flies along a given path with a certain degree of accuracy. The main focus was on three primary types of area navigation: LNAV (lateral), VNAV (vertical), and 4D navigation, which includes a time parameter. Key conditions for successful flight using this technology were also outlined.
Pros of area navigation
1
Flexibility
Allows aircraft to follow optimal routes, potentially reducing flight time and cost
2
Accuracy
Ensures a high degree of route adherence, reducing collision risks and allowing more efficient use of airspace
3
Automation
Automated execution of complex maneuvers significantly reduces the workload on civil aircraft pilots, where crew numbers are minimized
Cons of area navigation
1
Technical complexity
Requires high-quality navigation systems and a trained crew
2
Signal dependence
The aircraft must consistently receive signals, creating potential risks if lost
3
Need for certification
All RNAV and RNP systems must be certified, leading to additional costs
However, despite all the advantages of area navigation, modern requirements for aviation safety and flight efficiency pose the challenge of seeking new technological solutions.
One such solution is the GNSS (Global Navigation Satellite System) and its functional additions. These additions are seen as the key to improving accuracy, reliability, and integrity of navigation information, especially important in adverse weather conditions or in areas with a high degree of airspace congestion.
One such solution is the GNSS (Global Navigation Satellite System) and its functional additions. These additions are seen as the key to improving accuracy, reliability, and integrity of navigation information, especially important in adverse weather conditions or in areas with a high degree of airspace congestion.
What's the article about?
Chapter 1
Chapter 5
Introduction
As a strengthening link in the world of aviation navigation, Global Navigation Satellite Systems (GNSS) represent a potent tool, ensuring safe and efficient air traffic management. However, like any other technology, GNSS has its limitations and drawbacks. It's precisely to overcome these constraints that functional augmentations were developed.
Three primary types of augmentations - airborne, ground-based, and satellite-based - each with its unique application and functionality. Airborne augmentations, in particular, include Receiver Autonomous Integrity Monitoring (RAIM) and Aircraft Autonomous Integrity Monitoring (AAIM). These systems play a pivotal role in monitoring and ensuring the accuracy of data received from satellites.
Satellite-based augmentations, known as SBAS, operate by extending GNSS capabilities and providing additional information for enhancing accuracy and reliability. Ground-based augmentations, on the other hand, have a localized scope, as evidenced by the LCCS-A-2000 station, which allows for high-precision landing approaches. Some, like the Australian Ground Regional System (GRAS), might even have an extended area of operation, covering vast territories.
In a world where air traffic congestion is ever-increasing, these augmentations play a crucial role in ensuring flight safety and efficiency. They act as a bridge, linking technological constraints with the needs of a burgeoning aviation sector. Crossing this bridge, we delve deeper into understanding each of these augmentations in more detail.
In a world where air traffic congestion is ever-increasing, these augmentations play a crucial role in ensuring flight safety and efficiency. They act as a bridge, linking technological constraints with the needs of a burgeoning aviation sector. Crossing this bridge, we delve deeper into understanding each of these augmentations in more detail.
On-board augmentations to satellite navigation systems (ABAS)
In modern air traffic, navigation systems are an integral part of ensuring flight safety and efficiency.
However, since the main Global Navigation Satellite Systems (GNSS) cannot guarantee 100% accuracy and reliability under all conditions, there arose a need for onboard augmentations that help monitor and correct the information received.
However, since the main Global Navigation Satellite Systems (GNSS) cannot guarantee 100% accuracy and reliability under all conditions, there arose a need for onboard augmentations that help monitor and correct the information received.
Classification and Primary Functions
Satellite navigation systems are divided into classes: A, B, C. Each is designed for specific types of aircraft and corresponding tasks.
All these equipment classes have built-in functions for verifying the accuracy of information received from satellites.
All these equipment classes have built-in functions for verifying the accuracy of information received from satellites.
The primary method to achieve this is the use of Aircraft Autonomous Integrity Monitoring, or AAIM. Unlike RAIM, which requires a signal from at least five satellites to ensure information reliability, AAIM can manage with data from just four satellites. This approach ensures the ability to continue navigational calculations even with limited satellite visibility.
Combining with Other Systems
An additional way to enhance information reliability is by comparing GNSS data with information from other navigation systems, such as Inertial Navigation Systems (INS) or VOR/DME.
This data "reconciliation" is often referred to as "RAIM equivalent" or AAIM.
This data "reconciliation" is often referred to as "RAIM equivalent" or AAIM.
A significant augmentation to GNSS is the use of barometric altitude. This information can be used for "aligning" navigational calculations, "supporting" RAIM when data from a fifth satellite is lacking, or even for smoothing navigational definitions when only three satellites are visible.
Conducting RAIM Forecast
RAIM forecasting is at the heart of flight preparation. It's an assessment of the GNSS's operational readiness throughout the flight route.
Pilots use RAIM forecasts to determine the most accurate and reliable routes, especially when planning GNSS-based landing approaches.
The flight crew can check RAIM readiness for RNAV/RNP operations via NOTAM (if available) or through a GNSS forecasting service.
The flight crew can check RAIM readiness for RNAV/RNP operations via NOTAM (if available) or through a GNSS forecasting service.
Onboard augmentations to GNSS provide the necessary correction and control over data received from satellites. They play a pivotal role in ensuring flight safety and efficiency under various conditions and are a crucial link in modern aviation navigation. Alongside them, satellite and ground-based functional augmentations operate, which will be discussed next.
Ground-Based Augmentation Systems (GBAS)
Ground-Based Augmentation Systems (GBAS) are augmentation systems to the primary Global Navigation Satellite Systems (GNSS) that provide correctional information and GNSS signal integrity monitoring directly within a specific area, typically near an aerodrome.
The main objective of GBAS is to enhance the accuracy, integrity, availability, and reliability of GNSS data, allowing these systems to be used for approach procedures even in high precision conditions, such as ICAO categories IIIA/IIIB.
The main objective of GBAS is to enhance the accuracy, integrity, availability, and reliability of GNSS data, allowing these systems to be used for approach procedures even in high precision conditions, such as ICAO categories IIIA/IIIB.
- Local Area Augmentation SystemThis is the American version of GBAS, designed to enhance the accuracy of the WAAS system at the local level, especially during the approach to the final landing phaseLAAS
- GNSS Landing SystemThis is a landing system based on GNSS and uses GBAS for correction. It allows for landings in complex conditions that require high precisionGLS
Advantages of GBAS compared to Other Augmentations
GBAS provides high precision correctional signals, allowing aircraft to approach with a high level of accuracy.
As GBAS operates at a local level, it can offer data specific to a particular area, especially beneficial in challenging geographic or meteorological conditions.
Compared to some traditional navigation systems, GBAS can be more cost-effective in terms of infrastructure.
Disadvantages of GBAS compared to Other Augmentations
GBAS offers data only within a specific area, making them less versatile compared to other augmentation systems like SBAS.
As GBAS relies on ground stations, they can be susceptible to interference from local sources.
GBAS offers a valuable augmentation to primary GNSS, especially in areas where high navigation accuracy is needed. However, like any technology, GBAS has its pros and cons and is best suited for specific applications and usage scenarios.
Satellite-Based Augmentation Systems (SBAS)
Satellite-Based Augmentation Systems (SBAS) are navigational systems designed to improve the reliability, accuracy, and integrity of the information provided by Global Navigation Satellite Systems (GNSS).
They deliver correctional signals and essential integrity information through geostationary satellites, enabling aircraft pilots to determine location coordinates with a high degree of accuracy.
SBAS consists of three distinct segments:
SBAS consists of three distinct segments:
- SBAS geostationary satellites;
- ground-based infrastructure;
- onboard SBAS receivers.
The ground-based infrastructure includes:
The ground-based infrastructure comprises monitoring and processing stations that shape the SBAS space signal and receive data from navigation satellites, which calculate integrity, corrections, and ranging information. SBAS satellites relay data from the ground infrastructure to onboard SBAS receivers, which determine coordinate and time information using the primary orbital system(s) and SBAS satellites.
Onboard SBAS receivers acquire ranging information and corrections and use this data to determine integrity and refine the measured location. The ground network of SBAS measures pseudorange between a ranging source and an SBAS receiver set at a point with known coordinates and calculates individual corrections for ranging source ephemeris errors, clock errors, and ionospheric inaccuracies.
By providing differential correction signals, additional ranging signals through geostationary satellites, and integrity information for each navigation satellite, SBAS offers much higher operational service availability than the primary satellite constellation when combined only with ABAS.
- a network of ground reference stations that monitor satellite signals;
- master stations that collect and process the data from the reference stations and generate SBAS messages;
- communication stations that transmit these messages to geostationary satellites;
- transponders on these satellites that relay SBAS messages.
The ground-based infrastructure comprises monitoring and processing stations that shape the SBAS space signal and receive data from navigation satellites, which calculate integrity, corrections, and ranging information. SBAS satellites relay data from the ground infrastructure to onboard SBAS receivers, which determine coordinate and time information using the primary orbital system(s) and SBAS satellites.
Onboard SBAS receivers acquire ranging information and corrections and use this data to determine integrity and refine the measured location. The ground network of SBAS measures pseudorange between a ranging source and an SBAS receiver set at a point with known coordinates and calculates individual corrections for ranging source ephemeris errors, clock errors, and ionospheric inaccuracies.
By providing differential correction signals, additional ranging signals through geostationary satellites, and integrity information for each navigation satellite, SBAS offers much higher operational service availability than the primary satellite constellation when combined only with ABAS.
Description of the Operational Areas of Various Systems
WAAS (Wide Area Augmentation System): This system is designated for the North American region, particularly the USA territory. WAAS was developed by the US Federal Aviation Administration (FAA) to cater to aviation applications in all flight phases.
EGNOS (European Geostationary Navigation Overlay Service): EGNOS is a European system covering a significant part of Europe. This system was developed by the European Space Agency (ESA), the European Commission, and Eurocontrol.
SDCM (System of Differential Corrections and Monitoring): This is a Russian system designed to provide correction signals for the GLONASS system and other GNSS in the Russian region.
GAGAN (GPS Aided GEO Augmented Navigation): This system is developed for the Indian region and is aimed at enhancing navigation in aviation and other sectors.
MSAS (MTSAT Satellite-based Augmentation System): This system is designed for the Japanese region and is established by the Japan Civil Aviation Bureau.
EGNOS (European Geostationary Navigation Overlay Service): EGNOS is a European system covering a significant part of Europe. This system was developed by the European Space Agency (ESA), the European Commission, and Eurocontrol.
SDCM (System of Differential Corrections and Monitoring): This is a Russian system designed to provide correction signals for the GLONASS system and other GNSS in the Russian region.
GAGAN (GPS Aided GEO Augmented Navigation): This system is developed for the Indian region and is aimed at enhancing navigation in aviation and other sectors.
MSAS (MTSAT Satellite-based Augmentation System): This system is designed for the Japanese region and is established by the Japan Civil Aviation Bureau.
Key Characteristics and Their Impact on Aviation Navigation
- 1Enhanced AccuracySBAS correct errors related to signal distortion, Doppler effect, and other sources of GNSS inaccuracies.
This allows aircraft to precisely determine their location during all flight phases - 2IntegritySBAS quickly identify and inform users about any GNSS issues, ensuring the safe use of GNSS data in aviation
- 3ContinuityAugmentation systems guarantee a consistent and uninterrupted provision of correctional information, critically essential for aviation operations
- 4ReliabilitySBAS improve the overall reliability of GNSS by providing an added layer of verification and correction
- 5Global CoverageWith various regional SBAS systems, airlines and pilots can count on high-quality GNSS data anywhere in the world
SBAS are a crucial complement to global navigation satellite systems, offering a high degree of accuracy and reliability for aviation navigation. These systems play a pivotal role in the safety and operational efficiency of aircraft in civil aviation.
Conclusion
In the modern aviation industry, the importance of precise and reliable navigation cannot be overstated. As our analysis shows, satellite and ground-based augmentations play a pivotal role in enhancing the quality, accuracy, and integrity of data provided by global navigation satellite systems.
Satellite augmentations, like SBAS, offer a broad coverage area and enhanced accuracy over vast distances, whereas ground-based augmentations, such as GBAS, provide high precision at the local level, especially in the vicinity of airfields.
Nevertheless, like any technology, these augmentations have their pros and cons. Despite these, their implementation represents a significant leap forward in the realm of aviation safety and efficiency.
Transitioning smoothly to the next point, it's worth noting that the introduction of new navigation systems, particularly area navigation, inevitably brings about changes in the air traffic management system (ATM). These changes and their implications for the global aviation infrastructure will be discussed in the following section.
Satellite augmentations, like SBAS, offer a broad coverage area and enhanced accuracy over vast distances, whereas ground-based augmentations, such as GBAS, provide high precision at the local level, especially in the vicinity of airfields.
Nevertheless, like any technology, these augmentations have their pros and cons. Despite these, their implementation represents a significant leap forward in the realm of aviation safety and efficiency.
Transitioning smoothly to the next point, it's worth noting that the introduction of new navigation systems, particularly area navigation, inevitably brings about changes in the air traffic management system (ATM). These changes and their implications for the global aviation infrastructure will be discussed in the following section.
Area navigation
In the modern world of aviation, where safety and efficiency are integral parts of every flight, area navigation plays a key role.
This complex, yet extremely important element allows us to navigate airspace, minimizing risks and ensuring maximum safety for passengers and crew.
This complex, yet extremely important element allows us to navigate airspace, minimizing risks and ensuring maximum safety for passengers and crew.
Name of article: Functional augmentations
Release date: 8/17/2023
Acrticle author: Georgii Kurbatskii
Release date: 8/17/2023
Acrticle author: Georgii Kurbatskii
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