Global Navigation Satellite System (GNSS)-based technology measures the global position and, in some cases, the orientation of vehicles, assets and personnel that are equipped with GNSS receivers. GNSS-based systems rely on radio signals, which have been broadcast from satellites orbiting the earth. GNSS technology is often referred to as the Global Positioning System (GPS); however, GPS refers to the satellite constellation owned by the United States Government. There are several other satellite constellations in operation, with others scheduled for operation in the near future. Examples include the GLONASS (Russia), BeiDou (China) and Galileo (European Union) GNSS constellations.
Working Principles
GNSS-based technology typically consists of one or more antenna, a receiver and, in some cases, Inertial Measurement Units (IMUs). The various satellites broadcast information relating to their identity, time, status and orbit. Broadcast radio signals are received by the GNSS antenna and processed by the GNSS receiver to determine the global position of the GNSS unit. The information contained in the broadcast radio signals is used to measure the distance between GNSS-unit and the satellites. Line-of-Sight (LoS) from at least four satellites are required to measure the global position of the GNSS-unit. Some GNSS units include IMUs for enhanced localization performance. Other commonly used methods for enhancing the performance of GNSS technology is through the use of differential GNSS corrections and Real-Time Kinematic techniques, which require the use of additional GNSS and communication infrastructure.
In Proximity Detection System (PDS) applications, GNSS units need to be installed on both the local and remote object, and a communication link is required between the two objects. The global position of both objects is then used to calculate the proximity between the objects.
Advantages
- GNSS is a mature technology (introduced in the late 1970s) and a vast range of commercial solutions are available
- GNSS allows for Geo-fencing (defining no-go or restricted areas)
- Suitable for long-range applications
- Relatively high accuracy
- Inertial-based solutions can provide high-frequency positioning information as well as attitude (orientation) measurements
- Relatively robust to environmental conditions
Limitations
- Requires infrastructure to be installed onto remote object(s)
- Requires LoS to external infrastructure
- Not suitable for underground applications
- Performance may change depending on the status of the satellite constellations