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Ephemeris missing

6125703
over 2 years ago

My FR255 is showing "ephemeris missing" even after an hour activity with gps tracking and syncing several times with Garmin Connect Mobile on Android. I even tried powering it off and restarting, but another sync still didn't change the status.

This is the first time I tried to use the watch offline, without syncing for about 48 hours before using the gps only mode.

Doesn't Garmin save ephemeris being broadcast from satellites?  I am under the impression from other gps units that it should be possible after receiving for less than an hour. I expected to be able to use the watch in the mountains without any phone service for you to a week or two, so it's disappointing if it can't even handle a few days without the phone?

  • +1 over 2 years ago

    Uhh, where to begin?

    First of all, ephemeris means two things:
    1.
    “GPS satellites transmit information about their location (current and predicted), timing and "health" via what is known as ephemeris data. This data is used by the GPS receivers to estimate location relative to the satellites and thus position on earth.“
    2.
    “The Ephemeris Data can also be used to predict future satellite conditions (for a given place and time) providing a tool for planning when (or when not) to schedule GPS data collection.“

    https://cenv.wwu.edu/sal/gps-ephemeris-data

    The first thing always works. A GPS unit will always be able to find your position, if there are enough satellites visible. BUT time until finding the position (=fix) might take long - „cold start“ can be a minute or two.

    So the engineers thought of a way to speed that up, and there we are with the second thing: An „ephemeris file“, containing information about future satellite conditions. Your watch will know the date and time obviously, look it up in the file and have information about satellite constellation. This speeds up time until „fix“ to maybe 10-30 seconds, even with a „cold start“.

    “Ephemeris data is considered good for up to 30 days (maximum).“

    This file is NOT transmitted via satellite, or at least I never heard of something like that. As far as I know, it ALWAYS has to be synced via App or PC.

    6125703 said:
    My FR255 is showing "ephemeris missing"

    That is bad, as time to fix will be much longer.

    6125703 said:
    Doesn't Garmin save ephemeris being broadcast from satellites?

    As far as I know, nobody does.

    6125703 said:
    and syncing several times with Garmin Connect Mobile on Android

    That should not happen, it is a bug.
    Best tip I can give you: Try to connect the FR255 via cable to PC and sync it with „Garmin Express“. This fixed the problem for many, according to this forum, as the ephemeris file seems to be synced more reliable then.
    But still, it is a bug.

    6125703 said:
    I expected to be able to use the watch in the mountains without any phone service for you to a week or two, so it's disappointing if it can't even handle a few days without the phone?

    Of course it will always work and find your position, even if you never update the ephemeris file!
    It is only, that time to GPS fix can be much longer then.

  • 0 over 2 years ago in reply to Grumpy from dawn till dusk

    My experience with much older GPS receivers (without any USB port, etc.) was that they needed to receive for tens of minutes to an hour when you took them out of the box or out of storage.  But then you could turn them off for several days and when you turned them back on, they still could get a quicker fix. I assumed this was because the ephemeris data they had received was still fresh enough to not be a "cold start".

    To make things stranger, my watch still got its fix in about 15-30 seconds yesterday when the ephemeris is supposed to be missing. I wasn't timing it so cannot be more precise. It didn't feel much different than prior weeks when the watch indicated ephemeris current.

    Unfortunately, I don't have a Mac or Windows PC, only Linux.There is no Garmin Express offering for Linux though. And, I only see unanswered posts over multiple years when other people have inquired about this same problem.

  • 0 over 2 years ago in reply to Grumpy from dawn till dusk

    If you have the Music version, you can also sync it by WiFi without the phone.
    You can check if the watch has a current version of the file by looking into Settings - System - About. Scroll way down, and it should say Ephemeris: Current.

  • 0 over 2 years ago in reply to 6125703
    6125703 said:
    that they needed to receive for tens of minutes to an hour when you took them out of the box or out of storage.  But then you could turn them off for several days and when you turned them back on, they still could get a quicker fix.

    In my experience with that type of device it would rather be hours than days, but yes.
    That is the „warm start“ or even „hot start“.

    I SUPPOSE (but don’t know for sure), that a FR255 will also save this short term ephemeris data. But the

    6125703 said:
    "ephemeris missing"

    message means, the file with the long term data for 2-3 weeks is not there…

    6125703 said:
    Unfortunately, I don't have a Mac or Windows PC, only Linux.There is no Garmin Express offering for Linux though.

    Hmm, I am a Linux guy too, but to be honest: For firmware updates (various vendors) and Garmin Express (not primarily for the Forerunner, but for eTrex and Drive) I still keep an older Windows PC :/

  • 0 over 2 years ago in reply to ovekvam

    Unfortunately I have the non-music version so no WiFi. And that status screen is what I am talking about where it says "Ephemeris: missing".

  • 0 over 2 years ago in reply to Grumpy from dawn till dusk

    Do you know where Garmin Connect Mobile gets the ephemeris data?

    One other thing is I almost never have location enabled on my phone. So if the app gets it from the phone GPS subsystem rather than the internet, I guess that would explain it.

    But if that's the case, how long does phone location need to be enabled for it to recover? I don't want to be forced to leave all this stuff on all the time...

  • 0 over 2 years ago in reply to 6125703

    It comes from Garmin.

  • +1 over 2 years ago

    It's funny but it fixed itself while I was trying to make a video of the problem after a Garmin support chat. I must have synced it about 10 times in the last 24 hours, but it only changed from "missing" to "current" after the last attempt. I don't know if they somehow influenced Garmin Connect since I chatted with them or if that was mere coincidence.

    I did several rounds of initiating a sync from the device controls menu and then going back to the About screen to check the ephemeris status, while struggling to both operate the watch and keep it in view on the video. Maybe there is some delayed stuff still going on after the sync is indicated as complete...

  • 0 over 2 years ago in reply to 6125703

    I don't use the phone sync much, but I have the impression that the sync indicator on the front dashboard of the app shows finished after the activities are transferred, while the indicator under Garmin devices continues to show downloading of new firmware or other things.

  • 0 over 2 years ago in reply to ovekvam

    I never noticed that menu so don't know what it showed at the time. I thought the circle at the top of the dashboard around the icon of the watch was showing that device's sync status, since it brings up device settings if I touch it.

    Several of the syncs were initiated from the on-watch sync control and it showed the green sync complete status screen on the watch too. But the ephemeris didn't become "current" until about the third or fourth cycle of this.

    Between all these different GCM, watch, and CIQ screens, I wonder how many more different status values there are that we haven't discovered yet...  :-)