31 May 2016 |
Research article |
Aeronautics and Aerospace
The Impact of Satellite Positioning System Failures on our Lives
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Global Navigation Satellite System (GNSS) receivers are integrated into numerous applications and, therefore they take an increasing part in human habits. Every year, the whole market of GNSS products and services increases at a rate of about 25% . According to some predictions in 2020  more than 1 billion satellite navigation units will be in operation, driven by growth in emerging economies. Some factors are facilitating the growth of GNSS applications: receivers are more powerful, smaller, cheaper and easier to handle, emerging economies are growing, etc. They provide a strong impact in the countries’ development.
This article discusses the impact of GNSS critical applications on society, via critical infrastructures. This investigation will show how our society is becoming more dependent on GNSS applications. One problem concerning GNSS systems is their reliability. GNSS systems cannot work completely without fail. We will highlight the principal sources of the SATCOM and GNSS spectrum interference, the effect of its outage and its consequences. Finally, we will review current and new mitigation techniques capable of resolving SATCOM and GNSS spectrum interference issues.
Criticality of GNSS Applications
Applications using GNSS cover a large array of sectors including all kinds of transport (road, air, maritime and rail), energy production and distribution, advanced technologies (timing, scientific surveying, earth observation, network synchronization), safety of life (surveillance, defense, emergency and location-based services) and even social networking and recreation, as shown in Figure 1. GNSS technology is important in real-time predictions of real or possible critical situations and natural disasters. Moreover, GNSS applications are linked with all levels of human security in our society.
GNSS and Critical Applications
In society, a critical infrastructure is an area composed of equipment and systems that require the support of critical functions (applications) to satisfy basic needs of society and provide public safety. The critical infrastructures are vital to a nation’s security, economy and survival. There are 8 categories of critical infrastructures , which include the following sectors (refer to Figure 2).
We can summarize the GNSS impact on services and activities and the minimal degree of performance needed to accomplish them. In reviewing GNSS main applications, they can be classified in different criticality categories : Safety of life applications and Mission applications.
By definition, safety of life applications are those where failures or errors may directly cause harm, injury or death to humans: aviation, rail, maritime, emergency management (ambulance, fire, police, search and rescue), traffic surveillance, personal protection, etc. Basically, these applications are vital to people’s health and integrity. Their main characteristics are the following: they must be error-free (high integrity) in any circumstances. They also need high availability and high continuity. In the end, because of their criticality, the devices intended for safety of life applications must be certified.
Mission applications are those where failures or errors may indirectly affect people’s integrity or health by causing destruction of systems, damaging property external to the system, or damaging the environment. These applications are deemed vital to an organization’s business success or existence. They need to be highly accurate, highly reliable and highly available. They include industries such as: oil and gas, mining, environment, space, construction/civil, fisheries, precision surveying, precision agriculture, forecasting, geodesy, timing, fleet management, engineering, vehicle control, and robotics. These kinds of services need high accuracy, high precision and high reliability GNSS receivers to perform adequately.
GNSS technology can be related to numerous types of accidents. They are involved in distracted driving. For example, GPS devices being fallible, some errors can lead to outdated or inaccurate information for driving guidance and navigation. Because of these factors, GNSS devices can increase the risk of accidents and take the thought process out of the driving equation or awareness. For example, it is estimated that GPS units were directly involved in 300,000 car accidents in the United Kingdom alone, in 2008 . In addition, virtually hundreds of thousands of civil aircrafts rely on GNSS devices. GNSS applications can be classified as mission critical or safety critical, as shown in Figure 4.
Connection between Applications and Infrastructures
The relationship between GNSS services and society can be explained by the following steps, graphically described in Figure 4:
- We know that a society is composed of many institutions. Some of them are critical, as previously stated. An example of critical infrastructure is health and emergency services with ambulances.
- We know that many elderly people in our society use health and emergency services for assistance or for public care. Some of these services use GNSS signals for ambulance tracking and to track patient health via wireless devices (heart, blood pressure, temperature, etc.). These services are critical.
- So we can make the assumption that GNSS has an impact on critical health and emergency services (critical infrastructure) in our society.
- Knowing that GNSS is embedded in health services, emergency services, defense, transportation, finance, food production, energy production, environment surveying, all sectors vital to society, we can conclude that GNSS services impact society via crucial infrastructures.
GNSS Effects on Critical Infrastructures
Critical infrastructure, seeking the increased efficiency made possible by GNSS, has also developed a reliance on GNSS that can lead to serious consequences if the service is disrupted and the applications are not equipped with mitigating devices and procedures. There is a real dependency on GNSS services. If crucial infrastructures are affected (as it is described in Table 1), the people’s confidence towards the systems will gradually lower.
Table 1. GNSS description of effects on infrastructures
Sources of Space Spectrum Interference
The technology of radio navigation via satellite is becoming increasingly precise and accurate. But under some circumstances, GNSS receivers may fail to work properly. The main sources of failure or malfunction a GNSS user can encounter are the following:
- Source n° 1: System Malfunction
- Source n° 2: Hazards in Propagation Channel
- Source n° 3: Unintentional Interference
- Source n° 4: Intentional Interference
- Source n° 5: Human Factors
Space Spectrum Interference Mitigation Strategies
There is no magic wand to cancel undesired Radio Frequency Interference (RFI) from satellite communication and GNSS signals. The protection of satellite communications and GNSS requires a set of measures to deal with the various aspects of RFI: regulatory protection and efficient mitigation techniques.
To understand how the sources of space spectrum interfere with GNSS and what kinds of strategies can be used to reduce or eliminate those interferences, please read the Research Paper available in the Journal “Positionning“ at the following link:
Do Alexis Sanou, René Jr. Landry (2013). Analysis of GNSS Interference Impact on Society and Evaluation of Spectrum Protection Strategies. Department of Electrical Engineering, École de Technologie Supérieure (ÉTS), Université du Québec, Montréal (Qc), Canada. Positioning, 2012, (Positionning Journal article)
This article is also available via Espace ÉTS.
René Jr Landry
René Jr Landry is a professor in the Electrical Engineering Department at ÉTS and the Director of LASSENA. His expertise in embedded systems, navigation, and avionics applies notably in transportation, aeronautics and space technologies.
Program : Electrical Engineering