Just a very quick post to provide some context about an issue that some (but not all) see where recorded GPS tracks are offset by over a hundred meters or more. In general, the pattern of your route is correct, but it can be shifted to one side or the other. However, in many cases, after training, it resolves. In other words, it is largely a unique issue.
The problem seems to greatly affect companies that use the Sony GPS chipset in their devices, which are virtually all new Garmin devices in recent years, most new Suunto devices in recent years, all Polar devices in recent years, all COROS devices, Wahoo RIVAL and many others. More or less everyone except Apple.
Very hard list of affected devices (I’m missing a ton here, these are just the most popular)
– COROS GPS watches (you have to double check the 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 RIVAL
Again, I’m missing a load of boats here, but these are the ones with the big tickets in my head.
All these companies switched to the Sony GPS chipset around 2018, Polar and Suunto initially jumping on board, quickly followed by Garmin, COROS and many more. The Sony GPS chipset is widely used by these companies due to the energy savings that ensure a longer battery life.
But – that’s all except the subject, and not the cause of the problem. The problem is with the ephemeris data file, also called the EPO (Extended Prediction Orbit) file or Connected Predictive Ephemeris (CPE). Or simply the satellite’s pre-cache file. This is the file that is delivered to your device frequently (usually every few days). This file is what makes your watch find GPS satellites almost instantly when you go out. It is essentially a sheet of deception in which the satellites are for the next few days, or up to a week or so.
The bike clock or computer automatically receives this file via Bluetooth Smart from your phone, WiFi or USB, depending on how you connect your watch. Most companies deliver it every time your watch syncs and needs a new version. So, on your part, you never do anything – it happens quietly in the background.
At this point, the data in this file is incorrect, and therefore the data that the watch uses in the first few minutes is also wrong – leading to offsets. You can see an example of this below, from a DCR reader:
Because the watch stays connected to GPS satellites throughout your workout, in general, it will be corrected again as it extracts updated data from above. Most people report that it will be it is solved either at the end of the training or at the next training. You can see this from another DCR reader:
Same thing – identical errors at the starting point on my wife’s Fenix 6X Pro and Forerunner 45S, then sorting – I went, she ran, so my route is more accurate because she had more time to solve , I guess … pic.twitter.com/tZ4ysgYPtW
– ac72 (@ ac72) January 2, 2021
To solve this, you can simply stick your watch / bike computer out and let it record an hour of training, then throw it away.. You will receive the requested information via satellite to probably correct it.
But it will not impact everyone. For example, I tried today with two Sony watches (Garmin FR745 and FR945) to make it set an incorrect track – and it wouldn’t. I guess this is because, in my case, the clock was hit a few times while playing with my kids yesterday and today, so I guess it has already re-downloaded what was supposed to be right from the gate. I also tried with two non-Sony chipsets (Fenix 5S and Apple Watch SE) and I didn’t see any problems.
Talking to Garmin today, is working on a solution to this problem, which I think will most likely just update the pre-cached satellite data on the server, which in turn will take over your clock as usual. But first they (and the others) work to fix exactly what is wrong with the data that is causing this.
Talking to another person in the industry who deals with this issue, they noted that technically 2020 was 53 weeks old, and this is the 53rd week. As such, the suspicious issue with the Sony data file could actually be related to this complexity.
See … just when you thought you escaped 2020, it’s still waiting for you at the beginning of your run.
With that – thanks for reading!