GNSS: Advantages and Disadvantages

This page explores the advantages and disadvantages of GNSS (Global Navigation Satellite System). It details the benefits and drawbacks of using GNSS technology.

What is GNSS?

GNSS stands for Global Navigation Satellite System. It encompasses both global and regional navigation systems.

Global GNSS systems include:

• GPS (operational in the US)
• GLONASS (in Russia)
• BeiDou (in China)
• Galileo (in Europe)

Regional GNSS systems include:

• QZSS (in Japan)
• IRNSS (in India)

Global systems are often augmented by additional systems to improve accuracy. These augmentation systems include WAAS, EGNOS, GAGAN, and MSAS.

GNSS operates based on the concept of Time of Arrival ranging.

GNSS system architecture

The figure above illustrates the GNSS system architecture. As shown, there are three primary segments:

• Space Segment: This includes the satellites themselves. For GPS, GLONASS, BeiDou, and Galileo, the space segments differ in terms of the number of satellites and their coverage areas.
• Control Segment: This consists of monitoring stations and a master control station. The control segment maintains all information about the satellites and ensures they remain in their respective orbits.
• User Segment: This includes devices equipped with GNSS receivers, enabling them to determine their location using radio signals from the GNSS satellites.

Here’s a brief overview of some of the global systems:

• GPS: Employs approximately 32 satellites across six orbital planes. Primarily used in the United States.
• GLONASS: Uses about 24 satellites across three orbital planes. Operated by Russia.
• BeiDou: Utilizes around 22 satellites. Used in China.
• Galileo: Employs about 14 satellites. Developed by Europe. Offers more accurate positioning, especially at high altitudes.

Benefits or Advantages of GNSS

Here are the key benefits of using GNSS:

• Simultaneous Availability: All global navigation systems are available concurrently. GNSS leverages the advantages of all these systems, providing operators with increased access and availability of signals.
• Accurate Timing: GNSS provides precise timing information, which is crucial for developing high-precision IoT networks.
• Improved Navigation Solution Availability: Multiple GNSS constellations enhance the availability of navigation solutions. This leads to improved TTFF (Time to First Fix).
• Time and Cost Savings: GNSS delivers increased location accuracy at enhanced performance, ultimately saving time and money.
• Uninterrupted Connectivity: Multiple GNSS systems offer uninterrupted connectivity in various environments, including dense forests, vast open areas, and densely populated cities.
• Automatic Satellite Filtering: GNSS receivers automatically exclude any failed satellites from their navigation solution calculations.

Drawbacks or Disadvantages of GNSS

While GNSS offers many advantages, there are also some drawbacks:

• Limitations in Flight Applications: GNSS alone cannot support all phases of flight, especially those requiring stringent precision approaches. Therefore, augmentation systems are needed alongside GNSS systems.
• Insufficient Accuracy: The vertical accuracy of GNSS can be greater than 10 meters, which may not be sufficient for all applications.
• Need for Augmentation Systems: GNSS alone may not meet all requirements for availability, integrity, accuracy, and continuity. This necessitates the deployment of augmentation systems like ABAS, GBAS, and SBAS.
• Impact on Aviation Stakeholders: GNSS impacts aircraft operators, air traffic services, pilots, and regulatory personnel.
• Dependence on Navigation Database Accuracy: The safety of GNSS navigation relies heavily on the accuracy of the navigation databases used by the system.