Garmin Fenix 7 – is ‘All Satellites Mode’ More Accurate than GPS?

Must Read: Garmin Fenix 7 Review

In late 2021, the Coros Vertix 2 debuted the Airoha/MediaTek AG3335M GPS chip and, more recently, the Garmin Fenix 7 saw Garmin ditch the Sony chip in favour of Airoha, presumably, for the exact same one that Coros uses.

Every new sports watch and GPS chip seems to claim to be more accurate than the previous one but the truth is far from that. Indeed, over the last 5 years or so the focus has been on sports watches using components that use less power and hence extend battery life. As a result, accuracy has suffered, my Fenix 6 Pro (six) being a prime example of accuracy meh-ness.

Much talk has been made on how case materials and antenna design affect accuracy. Whilst true, there are many other factors at play including GPS algorithms and the use of available power.

Multi-constellation & Multi-frequency GNSS?

Airoha brings us two things of note that should increase accuracy – multi-constellation GNSS and multi-frequency reception.

Multi-Constellation GNSS accuracy is what this post looks at. My Fenix 7 is a non-Sapphire model and, as such, it does not have multi-frequency reception. I’ll save a look at multi-frequency accuracy later for my Garmin Epix 2 Sapphire.

Multi-constellation GNSS previously meant either GPS+GLONASS or GPS+GALILEO. Both combinations simply offer more satellites for your watch to find…the more the merrier when it comes to delivering accuracy in dicey reception conditions.

Well, now the Fenix 7 now has PLENTY of satellites to choose from. Probably for simplicity, Garmin gives Fenix 7 users the choice of GPS-only or GPS+every other constellation.

The Chinese Beidou satellites are now a global system and they are added to the full list that includes satellites from GPS (USA), GLONASS (Russia) and Galileo (EU) and if you like in India or Japan you might also benefit from NavIC and QZSS satellites.

To reiterate: multi-frequency is only on the Sapphire models. Multi-frequency improves accuracy differently to multi-constellation. Each satellite also transmits at the L5 frequency which is a different frequency to the L1 frequency. These different frequencies will be refracted and reflected differently to each other so if your watch finds a mismatch from any one satellite in the distances reported by L1 and L5 then information could be disregarded as being inaccurate.

Garmin Fenix 7 Accuracy

OK, I’ve bored you enough with satellite stuff. I’ve performed some workouts this week where I repeated a route with GPS-only and a  comparable ‘best’ mode with the Coros Vertix 2, Garmin Fenix 7, Apple Watch 7 and the 935. So for the Vertix 2 & Fenix 7, I used All constellations, I used the only available mode on the Apple Watch 7 and the 935 used Galileo in the hope it was better than GLONASS.

Test 1 – Suburban Grid – All Constellations

These are all fairly decent-looking tracks at a high level but the red (935) strays off the course more than the other 3 so I’ll remove that track for the subsequent zoom-ins.

Here are some more details where Fenix 7 (green), Vertix 2 (Yellow) and Apple Watch 7 (blue are compared). Of these 3 they are sometimes equal but on many of the corners the Vertix let me down slightly. The Fenix 7 probably edged out the Apple Watch 7 here and so was the best. I was surprised on two fronts. Firstly that the Apple Watch 7 (seven) performed well as I’ve found it to be not as good as the Apple Watch 6 and secondly that there was a clear difference between Coros and Garmin.

Now, don’t get me wrong here. I’m not belittling the Coros 2 or Apple Watch in any way. These 3 watches are some of the most accurate on the market today. I’ve done this test route many times and I’m pretty sure that the results you see here are generally superior to anything else currently sold by any other vendor’s watches.

Test 2 – Suburban Grid – GPS Only

This is the exact same route, in reverse and with GPS-only.

At a high level you can again see 4 similar tracks. You might even think they are not that much different from the previous test! And certainly, if all you are looking for is a pretty track on Strava then GPS-only is the de-facto recommendation.

Zooming in closer it was again the 935 that was clearly less accurate so I omitted that once again just to make these charts more readable. This time the winner is less clear cut but it is still the Fenix 7 with the Vertix 2 dropping slightly further behind.

Test 4, 5, 6 – Cycling

There’s nothing to see here folks! These 3 rides are all perfectly acceptable with only one glitch from the Wahoo Bolt 2. One ride is the Richmond Octopus which is 8 short but could-be-hard hill reps in a suburban town centre area, another is a 4 hour+ Surry hills ride with trees and hills and the last is a tempo ride from London to Windsor with no GPS challenges other than bad, bumpy roads.

Test 7 – Tall Buildings – All Satellites

Running close by tall buildings and encountering 6/7/8-storey high buildings in nearby Kingston is the closest I’m going to get to downtown Manhattan.

This image shows a bit more of a spaghetti mix of competing tracks and there is no clear winner at a high level despite them all just about agreeing on the approximate route. Even where the blue line appears to differ from the others it doesn’t mean it’s wrong in fact sometimes the blue line was correct and the others were not, although sometimes it was wrong as well!

One of the issues we look at in built-up areas is that of the effect of reflected signals from tall buildings. Just like your image appears to be behind a mirror so the GPS track is similarly affected by tall buildings although not quite in the same way. You will often find that if you run past a tall building on one side and a road on the other side, your GPS track will have you thrown out into the middle of the road. This is the effect of reflected signals.

The 935 (red) was close to the others this time but it was just the worst so, again, I’ve eliminated it to give clarity.

I can’t really decide which is best here. I’ve marked where tracks are in the wrong place or correct.

Apple Watch 7 (Blue) vs, Fenix 7 (Green) vs Vertix 2 (Yellow)

Test 8 – Tall Buildings – GPS

Here are the same watches and the same route, this time with GPS-only. Apple Watch 7 uses the same satellites as the previous test.

The yellow (Vertix 2) and Green (935) tracks are slightly worse so I’ll remove them for the detailed look which, remember, compares Fenix 7 GPS (Red)  to Apple Watch (Blue), the latter in ‘best’ mode. The Apple Watch probably does win this but it should as it is using a supposedly better mode.

Test 9 All-Satellites 10-mile test

Finally, this week is my formal test over a 10-mile route that has some quite tricky GPS reception issues in places.

The Fenix 7 turned in the second-ever best performance from a Garmin watch. The best is the 745. The performance is definitely not as good as the Ambit 3/Polar V800 from pre-Industrial Revolution days but Garmin has quite clearly closed the gap, as has Coros. With a bit more accuracy tinkering applied to their algorithms, Garmin and Coros might, just might, be ale able to match those old Polar and Suunto performances from years ago at some point toward the end of this year.

Full Methodology, results and data files here.

Test 10 – GPS-Only 10-Mile Test

Here’s the exact same test but on a different day and with GPS-only used. There’s not too much difference at first sight! In some cases, the GPS-only track is better. However, my strict scoring regime for key points on the route gives 73% for GPS-only (very average) and 81% for all-constellations (quite good). That might have been a bit harsh on GPS-only but All Constellations is a little bit more accurate.

So What?

Technology seems finally to be catching up with history.

Airoha probably has a chip that can match the performances of yesteryear, although it’s not quite there yet.

Will you get accurate instance pace? Hmmm. Probably not always, but you will start to get it more often. As always, if you want consistently accurate instant pace and distance then you need to use Stryd, if you want a pretty Strava track then do yourself a favour and save some battery juice and use the GPS-only mode. Those recommendations are unchanged.

I’m being a little unkind as Garmin really has made some quite significant strides here. Clearly, GNSS accuracy is now something they are focussing on and when Garmin focuses on something they eventually get it right. But the current situation is that Garmin’s GPS accuracy is probably pretty similar to everyone else right now rather than previously when it was a bit behind the competition.

Garmin product execs have recently been talking publically about their devices now having spare power to throw at the GPS chip. This is an important point, as with the spare power that is now available, Garmin and Coros can start to interrogate the chip data more intensively and use clever methods to weed out bad data points. The result is more accurate instant pace and distance.

This generation of chips might start to give us decent accuracy in forested areas but accuracy in urban canyons is probably still a tantalising step away from where we are today.

Q: Is ‘All Satellites Mode’ More Accurate than GPS-only for the Fenix 7?

A: Yes, but it doesn’t really matter.