GLONASS vs GPS *A SIMPLE ENGLISH EXPLANATION* – which is best and what is GLONASS anyway? As used by Garmin, Suunto and others

Garmin 920XT 735XT Optical ELEVATE

GLONASS is Russia’s version of America’s GPS. It is used to tell electronic devices where you are.

“GPS” specifically refers to the American system of navigational satellites rather than generic satellite navigation. We all use the term ‘GPS’ incorrectly in that sense.

GLONASS capability is increasingly used in high-end SMART devices, including the new Garmin Fenix 5 and Suunto SPARTAN.

GLONASS is neither particularly better nor worse than GPS.

HOWEVER, when they are used TOGETHER the likelihood of accuracy *IS* increased. Simply because there are more satellites available in both ‘constellations’ and hence a higher chance that your watch 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 LIKLIHOOD of achieving it MAY be increased.

Downsides: None really. Might use more battery power though depending on how well the watch manufacturer has optimised the navigational chip inside the device. Well…I say “none really” but, in my experience, turning on GLONASS does take a hit on battery that in many cases seem to reduce battery life to between 80 & 90% of ‘normal’.

Do I really need it? It will help with tree cover and nearby tall buildings. It may also help in mountainous areas or areas of high latitude (nearer to Arctic circle). I would say “It shouldn’t hurt” but, from my experience, often it does NOT SEEM to improve positional tracking

Don’t be fooled: Just because a device is advertised to have GLONASS doesn’t mean that much for the ACTUAL level of accuracy you will receive. There are VERY MANY OTHER factors that will affect this such as: quality of GPS/GLONASS chip; position of antennae; electromagnetic shielding within the device; algorithm used by the manufacturer of the end device. Indeed my anecdotal evidence is that sometimes GLONASS might lower accuracy.

Q: Why?

A: One of the factors is the quality of the manufacturer’s algorithm might be sub-par.

Don’t think it will make the running PACE shown on your watch more accurate. If you want accurate, instant running pace/speed then you MUST buy a footpod. The most super-accurate is STRYD  and the cheapest sensible option is the MILESTONE. And yes this advice STILL applies even if you’ve just spend £600/$700 on a top-end Garmin Fenix 5X…eesh.

ESSENTIAL READING: (Here) are my GPS/GLONASS tests on sports watches – as of 11Feb 2017 best performers so far are: TomTom Adventurer/Spark/Runner 3; Suunto SPARTAN Sport (not ULTRA); and Garmin’s Fenix 3.

Future: Europe’s Galileo system will come into action around 2020. Many chips currently enabled with GPS and GLONASS also support Galileo. GREATLY increased accuracy is hopefully going to happen then with 1m accuracy. HOWEVER my suspicion is that there will be an increased USER-cost associated with obtaining the 1m accuracy of Galileo and hence the extra accuracy may not be passed on to you or, if it is, you may well be charged more for it. Thus, for most of us, Galileo may well make no difference other than, like GLONASS, giving more satellites for us to see and get a higher chance of achieving the 4.5/5m accuracy that we should have had all along!

FWIW I have changed my usage of GLONASS in 2017 and indeed now I tend to turn it OFF. From my testing of several devices it seems that OFF is OFTEN more accurate. Plus turning GPS to ‘OFF’ better enables a like-for-like comparison with the accuracy of other devices. Having said that I would have it ON when navigating with a bike computer. and I would certainly turn it off on occasions where I am doing a long exercise that might be battery dependent.

SUMMARY: It’s a nice-to-have for most people that will make little difference.

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