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Galileo: Europe's version of GPS reaches key phase

another random user (2645241) writes | about 2 years ago

EU 1

another random user (2645241) writes "The third and fourth spacecraft in Europe's satellite navigation system have gone into orbit. The pair were launched on a Russian Soyuz rocket from French Guiana.

It is an important milestone for the multi-billion-euro project to create a European version of the US Global Positioning System.

With four satellites now in orbit — the first and second spacecraft were launched in 2011 — it becomes possible to test Galileo end-to-end. That is because a minimum of four satellites are required in the sky for a smartphone or vehicle to use their signals to calculate a positional fix."

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Great ! But, where are Galileo capable receivers ? (2)

macpacheco (1764378) | about 2 years ago | (#41645829)

Galileo is designed to be as compatible to GPS as it makes sense without including features that are extremely outdated into Galileo. GPS was designed in the 1970s, so 40 years later it would make sense to do things better.

GPS today broadcasts only one operational (healthy) civilian signal: L1 C/A. The L1 C/A signal is a pretty basic signal for today's technology, but it was state of the art in 1970s.

So Galileo doesn't broadcast L1 C/A at all, using L1C as its basic signal (same frequency band, quite different signal structure, far superior). E5a (same as the future L5 GPS signal) and E5b are also available, but use a different frequency, this might require two antennas or a more sophisticated one.

L1C will be supported by future GPS satellites (GPS IIIA and beyond), those satellites are still being manufactured, for launch 3-5 years from now (actual, realistic prediction, the US Air Force schedules says 2 years from now, but that schedule is for budget battles and for an extreme worst case of lots of satellites dying much faster than expected). Plus the Air Force plans to keep all new signals unhealthy until 18 satellites supporting that signal are operational, and that could take another 15 years easily. So don't count on L1C on GPS for as much as another 20 years !

In order to support Galileo, you need upgrades receivers that actually support at least L1C or E5a (the E5b signal will likely be used in conjunction with other signals, instead of used alone). For all low and medium cost receivers that means brand new hardwired circuits, its far from a simple software upgrade. You need a brand new receiver that supports GPS and Galileo.

The truly critical part of having 4 satellites available, is that GNSS receiver manufacturers designing Galileo upgrades are finally left with very little reason not to finish their work and release GPS+Galileo+GLONASS receivers (GLONASS is the Russian system). The launch schedule for the final operating version satellites is already defined, and should happen pretty quickly (fully operational in just 2 years or so). Designing a brand new receiver supporting Galileo could take that long from initial planning to delivery for sale.

Galileo is shaping up to be far superior than GPS and GLONASS, but using all three systems will always result in the most accurate results. Using all three, means knowing where you are in the world down to one meter (three feet) or less, even in situations when you don't have a great view of the sky, in times one system alone would be unable to provide you with a position fix at all. So if you already have GPS equipment, hold off on upgrades, until you have the option to buy a triple constellation version (there are already quite a few GPS+GLONASS receivers or dual constellation receivers). There's also a Chinese constellation, but China hasn't been playing very nicely in providing data for all but the Chinese vendors to design for their system.

Remember all the times when you're walking in New York, London, LA, Tokyo, Beijing, or other places full of very tall buildings and couldn't get a GPS lock ? Having all three (or even four) constellations available can be the difference from knowing where you are or not at all.

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