Galileo satellite navigation system - everything you need to know about the European GNSS

A total of 30 satellites are planned for the European Glalileo GNSS (Graphic: ESA).

What is Galileo satellite navigation? How accurate is it and how accurate is it compared to GPS or GLONASS? You will find out in this article. You will also learn how to get a satellite navigation device that works with Galileo. This article covers the basics of how Galileo works and the pros and cons of each system. We also look at the future of Galileo and what it means for industry.

What is the Galileo satellite navigation system?

What is Galileo satellite navigation? This global satellite navigation system was launched in October 2011. It is the most accurate system in the world, serving 2,3 billion users worldwide. Galileo has 26 satellites orbiting the earth at an altitude of about 23.000 km. These satellites are supported by sensors and terrestrial centers around the world. This makes Galileo an indispensable part of any transport system, because without Galileo millions of people would have been stranded and lost.

Galileo will provide users worldwide with free basic navigation services with an accuracy of one meter. In addition, users can take advantage of the system's improved location services, particularly at high latitudes. A unique feature of Galileo is its global search and rescue capability. If a person in distress is found, the transponder on the satellite sends a distress signal to the Rescue Coordination Center and initiates a rescue operation. The system then informs the user of the situation.

A Galileo ground station was inaugurated in November 2009 near Kourou, French Guiana. Since then, the number of Galileo satellites in orbit has increased. This has increased the reliability of the signals and the performance of the services. The system is expected to be fully operational by 2020, offering powerful services around the world. European Union transport ministers have agreed that the service should be fully operational by 2013. However, the latest press reports indicate that the commissioning will be delayed until 2014 at the latest.

So far, the Galileo system has three main functions: generating signals, transmitting signals, and storing and forwarding navigation messages. The Galileo ground segment sends navigation messages to the Galileo space segment, which sends signals with a specific Galileo signal structure. The Galileo space segment receives the navigation messages sent by the ground segment and sends them back to the satellites. High-precision atomic clocks on board the satellites control these functions.

How accurate is Galileo?

The accuracy of Galileo's satellite navigation is very good. Most of the error is caused by orbital errors and the other third is caused by clock errors. If the atomic clock is 3 nanoseconds behind, then the satellite looks a meter further away than it actually is. The accuracy is good enough to be used for navigation purposes, but it's still far from perfect. Galileo uses a high-precision ionospheric model called NeQuick. The resulting accuracy is comparable to that of GPS. The ephemeris are uploaded to the satellite several times a day to ensure high accuracy.

Here is an excerpt from the NeQuick ionospheric model, source: European Space Agency.
Here is an excerpt from the NeQuick ionospheric model, source: European Space Agency.

The Galileo system has been offering its services as part of the Initial Operational Capability (IOC) since December 2016. This is the first phase of the Galileo program. Positioning accuracy will be better than GPS, but the system still has problems. To date, only 21 of Galileo's 28 satellites are operational, meaning there will occasionally be gaps in coverage or poor positioning.

In March 2016, Galileo's accuracy was more than double that of GPS, but the system's improved interoperability with other GNSS systems has made it easier for users. For example, a receiver with multi-constellation capability can combine signals from multiple constellations to provide greater accuracy. the EUSPA also works closely with chip manufacturers to make Galileo compatible with current GPS receivers and to develop new ones.

The GSA is responsible for the maintenance of the Galileo system and publishes quarterly performance reports. The reports, while nice to look at, cannot prove Galileo's accuracy. For example, a recent failure affected only 5% of the Galileo satellites. While apologizing for the outage, GSA argued that Galileo is still in its early stages. However, most of the problems seem to be software-based.


Galileo and Russian GLONASS in comparison

The first question you should ask yourself is which satellite system is more accurate - Galileo or GLONASS? Both systems offer a similar level of accuracy, but have their own strengths and weaknesses. For example, while GPS provides better positional accuracy at higher latitudes, Galileo is more accurate at lower latitudes. The main difference between the two systems is the sensitivity, which plays an important role when choosing a satellite navigation system.

The advantages of Galileo are manifold. The higher accuracy is good for everyday products like cell phones and navigation systems. The emergency services will also benefit from this. European roads and railways will be safer thanks to Galileo services. Galileo will boost innovation and promote new products in Europe, so that in 2021 Europe will have a larger share of the global GNSS market.

The PDOP value for each system shows how many satellites are visible for 24 hours. Both GPS and GLONASS returned the highest number of satellites available, but the results were close. In this example, GPS provided the highest availability of satellites, while GLONASS and Galileo had similar visibility values. In the case of a GPS-GLONASS combination, they provided similar results.

Another important difference between Galileo and Glonass is the frequency of the signals. Glonass has a much lower frequency, but it doesn't work as well as Galileo. Galileo offers more precise signals, but it also requires a larger constellation of satellites. In order to get the best possible position data, a satellite needs to “see” four satellites.

A total of 30 satellites are planned for the European Glalileo GNSS (Graphic: ESA).
A total of 30 satellites are planned for the European Glalileo GNSS (Graphic: ESA).

Galileo and American GPS compared

The Galileo satellite navigation system, which will replace GPS satellites, is a GNSS constellation owned by the European Union. ESA, the European Space Agency, will build and operate the constellation, which will eventually have 30 operational satellites and six spare satellites in orbit. The Early Operational Capability was introduced in 2016 and is expected to be fully operational by 2020.

The European Union (EU) has its own concept for satellite navigation. She has divided the service into five categories: L1, L2, E5, E5A and E5. The signals will be compatible with the L1 GPS signal and the upcoming L5 signal. The European Union has defined these five levels, which it calls open services. This means that the signals can be used freely. However, this also has some disadvantages.

The difference in accuracy is not significant to users. A receiver must be linked to at least four satellites to determine its location. Devices with multiple satellites are faster and more accurate. Depending on the situation, one system may work better than the other in an urban environment. Also, GLONASS and Galileo are more accurate in urban areas. The GPS is often paired with a GNSS to provide users with better navigation accuracy.

The EU is not the only country using Galileo. Ukraine and Morocco have joined the project. Morocco has also joined the program and has a single service center in Madrid. While the UK and EU are at odds over the exact budget allocation for the project, there are signs the EU is considering more funding for the scheme.

What speaks for Galileo?

Here I simply quote the EUSPA website:

Galileo provides improved position and time information that will benefit many European services, businesses and users. An example:

  • Thanks to the multi-constellation of receivers that Galileo contributes to, users can now determine their exact position with greater accuracy.

  • Galileo's dual-frequency capability offers significant advantages in terms of the achievable accuracy, but also in terms of improved interference immunity.

  • The products people use every day, from the GPS in your car to your cell phone, benefit from the increased accuracy that Galileo offers.

  • Critical emergency services benefit from Galileo.

  • Galileo helps make Europe's roads and railways safer and more efficient.

  • Galileo boosts European innovation, contributes to the development of many new products and services, creates jobs and allows Europe to have a larger share of the world market for value-added services, which is forecast to reach €2029 billion in 166 (source: GSA GNSS Market Report Issue 6).

Alternatives for Galileo satellite navigation

A study published by the University of Sussex proposes an alternative to Galileo that would be cheaper, offer comparable levels of reliability, continuity and availability, and be five times more accurate. Prof Chris Chatwin from the University of Sussex presents his plans for an SBAS to be hosted on a national satellite. Such a system would be a cheaper alternative to Galileo, which is scheduled to be launched in 2026.

However, Galileo developed slowly and was marked by controversy and political disputes. Also, it's plagued by PR images of men in suits signing contracts. Despite these difficulties, the European Space Agency has launched four of the 30 satellites originally planned and is tasked with launching another 22 to complete the constellation. The satellite constellation is expected to have eighteen operational satellites by the end of 2014 and 2015 by the end of 26.

These systems are based on the same technology, which means that you can easily find and navigate around them in an unfamiliar city. However, one should keep in mind that GPS and Galileo are not suitable for use in areas where there are few or no cell towers. While GPS and Galileo are effective when traveling in urban areas, they are ineffective in sparsely populated or dark areas.

While the European Union is supporting the development of the Galileo project, it should not be forgotten that it is a largely civilian system, not military oriented. For example, 26 of the thirty satellites that will make up the system will be operational as early as 2020. The European Space Agency (ESA) has said it intends to make the European positioning system five times more accurate than GPS. It is therefore important to know that this system will not replace GPS in any country.



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