Ephemeris missing

I would say that ephemeris on the phone was missing? I would go outside and do a GNSS fix with the phone app. If GC has no data, it cannot pass it on the watch. Would also control positioning permissions for GC.

global_local said:

I would go outside and do a GNSS fix with the phone app. If GC has no data, it cannot pass it on the watch. Would also control positioning permissions for GC.

No.

All of that has clearly nothing to do with the „ephemeris file missing“.
This file is not generated at your phone. It is provided by Garmin and Garmin gets the satellite information from specialized services and „just“ needs to convert it to a format, their devices can read.
This file is also provided for devices like eTrex and will be synced with Garmin Express on a PC - which obviously has no GPS data itself.

If you know the format, you could even create an ephemeris file yourself, the satellite infos for GPS, Glonass, Galileo etc. are available on the net, see the site I posted above.

What MIGHT be the case: That the Phone provides ADDITIONAL aGPS (=assisted GPS) information to the watch, when synchronizing. That means an info like „You are now in the range of position ….“, which will of course also help to speed up getting a fix, because the device already knows it is at e.g. New York City, Manhattan, Hudson River.

Grumpy from dawn till dusk said:

This file is not generated at your phone.

/smartass mode on/

Nobody says that. To get the file you need your approximate location to make an request. For this you need position of your phone (+-100km). Where does the file come from I don't care. But if you don't have permission to request position, you can't make a request either. That's why I wanted to point out this point. ;)

/smartass mode off/

So the ephemeris file is location specific? There has been some global issues with these files before, where they are wrong all over the world because of a bug in the file (like wrong week number).

I found this info on a Garmin site: "Satellite location information is refreshed periodically when your Garmin product syncs data with your Garmin Connect account. This data needs to be refreshed if the product has not been used in over 30 days, or when it has traveled more than 200 miles from its last satellite connection."

Right, I saw that documentation as well. It talks about "the product", not "the phone".  But now I wonder if they are consistent with that in the GCM app to use the watch's last location to localize the ephemeris download process.

I do usually have the Android location toggle disabled unless I am actively trying to use mapping software, just like I have the bluetooth toggle disabled unless I am actively trying to connect to someting. So, if this silently prevents GCM from being able to produce an ephemeris file, that's annoying.

The 200 miles thing is also annoying. I wish these products did not assume online functionality like that. My usual trip to the mountains could be 200 miles of driving which ends up out of phone service range and staying there for a week or two. I can easily see that I am going to mess this up and forget to do a watch sync before I lose network service but close enough to my destination area.  They should have some kind of prefetch function to select an area on a map and get data ahead of time, much like tools to select offline map regions.

I do the same as you. Location and bluetooth are off by default in my devices unless i am actively using them. I do however have the Music-edition of the Forerunner 255, so I use WiFi to keep it updated. I have WiFi always enabled, but automatic sync off, so it is only used when I ask it to sync.

global_local said:

/smartass mode on/

Nobody says that. To get the file you need your approximate location to make an request.

Ok, good point.

If you had written that in your original posting, I would not have misinterpreted what you meant…

But still one question remains:

How can Garmin Express on a PC deliver the right ephemeris file for a device, if it doesn’t have a GPS based location?

Like I suggested above, I wish they anticipated travel to no signal areas and let me prefetch the ephemeris before my trip. That should allow for large travel distances within the 30 days without assuming I'll have Internet when I get to the new region.

Maybe something like picking zones on a map so GCM can fetch multiple files and then provide the right one to the watch during later syncs without internet.

Or maybe something like allowing the watch to sync and store multiple ephemeris files for different regions and switch between them. Maybe an option to get region files to cover all loaded courses?

Maybe Garmin Express asks the watch for location for the Ephemeris file?