New 2021 GPS accuracy issue affecting some Garmin, Suunto, and other GPS devices

Just a very quick post to provide a little context about an issue some (but not all) people see where your recorded GPS route is offset by a hundred meters or more. In general, the pattern of your path is correct, but it may get shifted to one side or the other. However, in many cases upon completion of the exercise, it excretes itself. In other words, it’s mostly a one-time problem.

The problem seems to be affecting to a large extent the companies that take advantage of Sony GPS chips in their devices, which are basically all the new Garmin devices in the last few years, most of the new Suunto devices in the last few years, all the Polar devices in the last few years, all the COROS devices. The Wahoo RIVAL and more. More or less than everyone except Apple.

Approximate list of affected devices (I miss a lot here, these are just the most common devices)

– COROS GPS watches (need to check back original Pace)
– Garmin Forerunner 45/245/745/945 / Fenix ​​6 / MARQ / Vivoactive 3/4 / Venu
– Garmin Edge 130 Plus 530/830/1030 Plus
– Polar Vantage V / M / V2, Grit X, Ignite
– Suunto 5 and Suunto 9
– Wahoo competitor

Again, I miss a boatload here, but those are the big tickets at the top of my head.

All of these have switched over to Sony GPS chipsets around 2018, with Polar and Suunto jumping in at first, quickly followed by Garmin, COROS, and more. GPS chipset from Sony is widely used by these companies due to the energy saving that provides longer battery life.

But – that’s all along with the main point, not the cause of the problem. The issue has something to do with Ephemeris data file, Also called an EPO (Extended Prediction Orbit) or Continuous Predictive Almanac (CPE) file. Or simply the satellite pre-cache file. This is the file that gets delivered to your device most frequently (usually every few days). This file is what makes your watch find GPS satellites almost instantly when you go out. It’s basically a cheat sheet about where the satellites are for the next few days, or up to a week or so.

A watch or bike computer gets this file automatically via Bluetooth Smart from your phone, WiFi or USB, depending on how your watch is connected. Most companies offer this any time your watch is syncing and you need a new version. So on your part, never do anything – it just happens quietly in the background.

Right now, the data in this file is wrong, so the data your watch is using for those first few minutes is wrong as well – which creates offsets. You can see an example of this below, from One DCR reader:

And another:

Since the watch maintains its connection with GPS satellites throughout the exercise period, It will generally correct itself As it pulls the updated data from the top. Most of the people report it Resolve itself either at the end of the exercise or the next exercise. You can see it here from another DCR reader:

Same here – identical starting point errors on my Fenix ​​6X Pro and my wife’s Forerunner 45S, then they sort themselves – I walked, ran, so my route was more accurate because it had more time to get a fix I guess … pic.twitter.com/tZ4ysgYPtW

– ac72 (@ ac72) January 2, 2021

To help solve this, You can simply tape your watch / bike computer to the outside and let it record a workout for an hour, then throw it away. It will likely have received the satellite information needed to repair itself.

But it will not affect everyone. For example, today I tried using 2 Sony watches (Garmin FR745 and FR945) to get them to trail incorrectly – and they won’t. I suspect the reason for this is that in my case, the watch got bumped several times while playing with my kids yesterday and today so I think it has re-downloaded what it needs to be correct outside the gate. I’ve also tried two non-Sony chipsets (Fenix ​​5S and Apple Watch SE), and I didn’t see any problems either.

Speaking to Garmin today, They are working on fixing the problem, Which they think will most likely only update the cache satellite data from the server, which in turn will get your watch just like you always do. But First, they (and others) work to pinpoint the exact data error that is causing this.

Speaking to another person in the industry who is dealing with this issue, they indicated that technically 2020 has 53 weeks, and that is the 53rd week. As such, a suspicious Sony data file issue may already be related to this complication.

See … just when you thought you ran away from 2020, he’s still out there waiting for you at the start of your run.

With that – thanks for reading!