Global Positioning System (GPS), Global Navigation Satellite System (GNSS), Ground-Based Augmentation System (GBAS), and Wide Area Augmentation System (WAAS)

   We have extensively studied GPS/GNSS, GBAS, as well as WAAS and have published on the matter to be of value-added proposition to the aviation and aeronautics ecosystem; we also have two granted patents: US 11,728,878 B2 "Systems and Methods for Locally Suppressing Interference in Radio Frequency Communications by Satellites" and US 12,007,486 B2 "Systems and Methods for Synchronizing Satellite-Based Clock Devices." GPS/GNSS Assessment Services have been one of our mainstay competencies, and some background information is provided as follows.


Source of figure: Federal Aviation Administration

Global Positioning System (GPS)/Global Navigation Satellite System (GNSS)

   Global Positioning System (GPS) (formally known as the Navstar Global Positioning System) refers to a space-based radio-navigation system, which is comprised of a constellation of satellites and a network of ground stations. GPS satellites orbit the Earth at an altitude of approximately 11,000 miles. GPS is operated and maintained by the U.S. Department of Defense. Established by presidential directive, the National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT) coordinates GPS-related matters across multiple federal agencies to ensure that the system addresses national priorities as well as military requirements. The National Space-Based Positioning, Navigation, and Timing (PNT) Executive Committee manages GPS, while the U.S. Coast Guard acts as the interface to the public for civil GPS service matters. The Federal Aviation Administration (FAA) Satellite Navigation Team provides GPS-based PNT in the United States to enable performance-based operations for all phases of flight ranging from en route, terminal, approach, to surface navigation. GPS-based PNT services are being examined for the purposes of overcoming the deficiencies in today's air traffic infrastructure and supporting implementation of the Next Generation Air Transportation (NextGen) system for the U.S. National Airspace System (NAS).


   In essence, GNSS (Global Navigation Satellite System) is an overarching term that refers to various satellite-based Positioning, Navigation, and Timing (PNT) systems, whereas GPS tends to refer to the U.S. satellite constellation. Manufacturers of precision timing products tend to now offer products that support the broader ecosystem of GNSS (not just GPS). As an example of our GPS/GNSS Assessment Services, traditionally, we have worked with a variety of GPS receivers for airport/airfield-related substation applications. Typically, high-stability oscillators are used to maintain continuous operation even during input signal loss. Some manufacturers allow for multiple input sources (beyond dual input sources), wherein various resiliency schemas can be employed. This capability is often termed Multi-Reference Sources (MRS). As the specifications vary, and some manufacturers have contended with various Common Vulnerabilities and Exposures (CVEs), such as listed on the National Institute of Standards and Technology (NIST) National Vulnerability Database (NVD), depending upon the requirements of the application and client specifications, we may make certain recommendations as to the apropos GPS/GNSS schema to utilize.


Source of figure: Federal Aviation Administration

Ground-Based Augmentation System (GBAS)

   Ground-Based Augmentation System (GBAS) (formerly known as the Local Area Augmentation System) is a system that provides differential corrections and integrity monitoring of Global Navigation Satellite Systems (GNSS). GBAS provides navigation and precision approach service in the vicinity of a host airport and broadcasts its differential correction message from a ground-based transmitter, via a very high frequency (VHF) radio data link. Current FAA-approved GBAS simply monitor and augment the legacy GPS civil signal, which is broadcast by all satellites. The original GPS design contains two ranging codes: the Coarse/Acquisition (C/A) code, which is freely available to the public, and the restricted Precision code (P-code), which is usually reserved for military applications. The C/A code is transmitted on the L1 frequency as a 1.023 MHz signal and is referred to as an L1 C/A broadcast.


   The FAA notes that "GBAS provides a satellite-based GPS alternative to the Instrument Landing System (ILS)." As part of the assessment reports, for which we have served as the principal performer, we have documented GPS/GNSS/GBAS issues for various International Air Transport Association (IATA) codes. For example, for one IATA code, we were asked to review the findings from a Frequency Spectrum Management Panel (FSMP) Working Group regarding GPS interference/signal degradation during the Area Navigation (RNAV) GNSS instrument approach phase, which resulted in unreliable Actual Navigation Performance (ANP). Along this vein, we have also conducted assessments regarding potential sources of interference.


Source of figure: Federal Aviation Administration

Wide Area Augmentation System (WAAS)

   The Wide Area Augmentation System (WAAS) is a system that provides navigation services across all of the U.S. National Airspace System (NAS). The WAAS provides augmentation information to Global Positioning System (GPS)/WAAS receivers to enhance the accuracy and integrity of position estimates. The signals from GPS satellites are received across the NAS at various Wide Area Reference Stations (WRS) sites. The GPS information collected by the WRS sites is transmitted to WAAS Master Stations (WMS). At the WMS, an augmentation message is created (the WMS generates a WAAS message broadcast or WAAS User Message every second). These augmentation messages contain information enabling GPS/WAAS receivers to remove errors in the GPS signal, thereby allowing for a significant increase in location accuracy and integrity. The augmentation messages are sent from the WMS to uplink stations for transmission to navigation payloads on Geostationary (GEO) communications satellites. The navigation payloads receive and then broadcast these augmentation messages on a GPS-like signal across the NAS. GPS/WAAS receivers process the augmentation messages as part of position estimation. The GPS-like signal from the navigation transponder can also be used by GPS/WAAS receivers as an additional source for calculation of a user's position. GPS/WAAS receivers can achieve position accuracy of a few meters across the NAS. WAAS also provides indications to GPS/WAAS receivers of where the GPS system is unusable due to system errors or other operational impact effects.


   The WAAS is the U.S. implementation of a Satellite-Based Augmentation System (SBAS), which is a geosynchronous satellite system that enhances basic GNSS (e.g., GPS) signals, via corrections to sources of error (e.g., clock drift, ionospheric delay, etc.) and a "certified level of integrity." SBAS can be especially useful for remote (whether terrestrial or oceanic) expansive areas. Apart from aviation, our experience with SBAS has been in the area of precision agriculture and autonomous vehicles.

We perform assessments

   Over the past several years, we have performed assessments at airfields around the world. In particular, our core competencies center around Global Positioning System (GPS) Assessments, Energy Resiliency Assessments, and Cyber Electromagnetic Spectrum Assessments. Our assessment methodologies have been affirmed by various governmental teams around the world and were feted at a scientific academy.

  • Our vision

    To become a premier service provider to the aviation community.

  • Our mission

    To provide value-added proposition to the aviation and aerospace sector, via certain assessment competencies.

  • Our assessment core competencies

    We are continually honing our skills in the field and are active within our sector. We specialize in using AI-centric tools and methodologies in our assessment work.

  • Our dedication to the community-at-large

    Our work over the past several years has had a definitive impact in enhancing resiliency at airfields around the world. We look forward to the privilege and honor of serving the aviation and aerospace communities as well as the global community-at-large for many years to come.

Contact Us

by email: info@vtaviationaerospace.com
by phone: +619 550-3058

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