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GPS III Explained – What is GPS III?
What is GPS III (GPS 3)?
GPS III is America’s upgraded GPS system which will perform with a similar level of accuracy to Europe’s GALILEO. It is used to enable electronic devices to tell you where you are.
As of 2019/2020 the term “GPS” specifically refers to the current GPS II (GPS 2) system of American navigational satellites. We all use the term ‘GPS’ incorrectly in that sense. GLONASS is Russia’s version and GALILEO is Europe’s version. The correct term that we should all use is GNSS rather than GPS. GNSS stands for Global Navigation Satellite System. GLONASS is a GNSS, GPS is a GNSS and GALILEO is a GNSS. There are other regional systems too.
These systems can be used on their own but increasingly they can be combined.
Thus GPS+GLONASS usage is now fairly widespread in sports devices and GPS+GALILEO is now increasingly used in high-end SMART devices in phones and sports watches, including the new Garmin Fenix 6.
Let’s first talk a LITTLE bit about ACURACY, GLONASS and GALILEO as that then better sets the picture to explain where GPS III will fit. I’m also going to tbe talking about sports smartwatches but the exact same principle applies to car satnavs, smartphones and other handheld navigational devices.
NB: I’m using the term GPS to mean GPS II from now on…
There are many factors affecting the positional accuracy you will experience with your device on the ground.
I want you to put in the forefront of your mind two factors, namely the NUMBER of satellites and the transmission frequencies the satellites are using. It seems obvious that the number of satellites you use will increase accuracy (it’s not strictly true though) and the other point to bear in mind is that if two frequencies of positioning signals are used then there is a bit of physics that will mean that you will be able to reduce accuracy losses from the route the signal takes (ionospheric delay) to reach your device from the satellite.
Detail on accuracy eg looking at HDOP, PDOP
GLONASS is neither inherently better nor worse than GPS (GPS II)
HOWEVER, when GLONASS and GPS are used TOGETHER the likelihood of accuracy IS increased. Simply because there are more satellites available in both ‘constellations’ of satellites and hence a higher chance that your watch/smartphone will be able to see enough of them for a good positional fix.
It is said that using GPS+GLONASS can give accuracy down to 4.5/5m and can also improve accuracy in built-up areas; especially in the Northern Hemisphere. That is THE SAME level of accuracy as standalone GPS. It’s just that the LIKELIHOOD of achieving it MAY be increased.
GPS+GLONASS is NOT more accurate than GPS alone – I have consistently found that in my product testing here
GALILEO & GALILEO Accuracy
As of Q4.2019 Europe’s GALILEO constellation is nearly complete with the final 2 (of 30) satellites expected to be operational in 2020. However, 24 satellites are all that is required for the system to be fully live and, as far as I know, that is the situation now.
The same principle applies with using GALILEO satellites alongside the GPS ones as it did for GLONASS…the more the merrier.
HOWEVER, we have the potential for AWESOME levels of accuracy to better than +/-1m, even in cities, because of the use of dual frequencies. GALILEO has 3 frequencies and two of them, E1 and E5a, can be used together with the L1 and L5 frequencies from GPS.
Unfortunately, in order to achieve that, a special chip is required such as the Broadcom BCM47755. And whilst that chip IS eventually intended to be used in wearables, I don’t know of any wearables that use it right now. It is used in some smartphones such as the Xiaomi Mi 9.
The current situation right now with wearables is that the Sony CXD5603GFchip seems to be the de facto standard for GPS and GALILEO signals received by Garmin, Coros, Polar, Suunto and others. Whilst this Sony chip is very low-powered and GALILEO-enabled it does NOT support dual frequencies AFAIK. Consequently, the levels of accuracy we see are largely unchanged from the GPS chips in the wearables of 5 years ago…although the power consumption is dramatically lower and it is power consumption and battery life that is driving wearable tech usage NOT ACCURACY. 🙁
SBAS and Accuracy
SBAS? Where did that come from?
I threw that one in. SBAS is a mildly important factor that might further improve GPS accuracy which can be enhanced if corrective readings are available to be taken from ground-based transmitters. This is performing a similar task to a dual-frequency signal from satellites but instead from the ground. The availability of these ground-based signals will be less than that from satellites.
What is GPS III (GPS 3)?
Originally planned for 2014, the next generation of American GPS satellites, built by Lockheed, is finally being launched into orbit. One has already been launched by SpaceX and one last month by ULA. 8 more are planned with SpaceX sending up the next of those in January 2020. These should all be operational in 2023.
Beyond 2026 will see a further 22 GPS3F satellites take to the sky, culminating with the last launch around 2034.
GPS III has been designed to use the same mid-point frequencies as already used by GPS and GALILEO. Thus, from a consumer device standpoint, we should effectively just see this as an expansion of the existing GPS and GALILEO systems ie the availability of even more satellites. eg I’m hoping that the aforementioned Sony GNSS chip will ‘just work’ with GPS III
But these new GPS III satellites also open up a new civilian frequency – L2C.
Edit: Added/changed after original text due to comments below, I wasn’t planning to talk about dual-band GNSS too much
The following chart attempts to show that Galileo E1 and GPS L1 can be used together as ‘one band’ and that Galileo E5a and GPS L5 can similarly be used together or individually as another band. By inference E1+L1 and E5a+L5 and L2c represent 3 bands that give us more scope for better accuracy derived from dual-frequency signals
|Galileo||GLONASS – K||GPS II||GPS III|
|1.559–1.592 GHz (E1)||1.593–1.610 GHz (G1)||1.563–1.587 GHz (L1)||1575.42 MHz L1 (Civilian)|
|1.237–1.254 GHz (G2)||1.215–1.2396 GHz (L2)||1227.6 MHz L2C (Civilian)|
|1.189–1.214 GHz (G3)|
|1.164–1.215 GHz (E5a/b)||1.164–1.189 GHz (L5)||1176.45 MHz L5 (Civilian)|
|1.260–1.300 GHz (E6)|
From the comments below there are more smartphone chips than I thought that are dual-frequency GNSS ready/enabled. As well as the BCM47755 chip that I specifically mentioned as its specs claim readiness for WEARABLES, there is also the Snapdragon 855 (from 2018), the Huawei Kirin 980 (from 2018) and Huawei Kirin 990 (from Sep 2019). I’m assuming these are dual-frequency GPS+GALILEO (not GPS III) …so this section is going off at a bit of a tangent to the original intention.
If anyone can send me some dual frequency workout tracks GPX/TCX from a smartphone and a separate track(s) from a sports watch on the same RUN/Ride…I’d love to put up some comparative images here.
GPS III will bring more satellites into view, enabling many devices to stand a better chance of achieving current levels of GNSS accuracy ie +/-5m
When combined with a suitable consumer GNSS chip that can handle multiple frequencies, the opportunity to receive high precision readings will exist.
Opinion? – Contain your excitement for a year or two more. Sports-GNSS usage needs to see the adoption of a more capable GNSS chip beyond the Sony chip used widely in 2019. It’s more likely that we will first see this innovation in smartphones, with sports devices a year or so behind. Finally, let’s not get too hung up on the satellite signals, we see BETTER RESULTS FROM 5 YEARS ago with GPS-only sports watches, clearly all sports watch manufacturers need to look closely at, for example, the design of their antennae.
For Mirko 😉
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