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Garmin Forerunner GPS Tracking Issues
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Hi

i'm looking to get some other people's expertise and experience to understand what i'm getting.
I had a FR920 and experienced intermittent issues with delays initially picking up satellite reception pre-run, then intermittent loss of tracking mid-run. ie it would pick up satellites pre-start and be tracking nicely for a time, then suddenly have me disappearing off into the middle of the ocean or the like mid-run, sometimes coming back on track later.

after getting no real support from garmin (basically they said "its an old device, bad luck"), i decided to upgrade to a FR935 hoping that the newer device would solve this. unfortunately i have already had a significant instance of the exact same behaviour on my 935.

a couple of things i've noted about the times it fails:
- all have been long sessions - a run at the end of a HIM and long standalone runs - and the error periods have always been well into it. doesn't seem like that should be relevant on a device supposed to be appropriate for slow IMs
- in one instance i went through a ~100m tunnel just before it lost tracking, others had terrain around that could have interfered with satellite reception but not to the point of near complete loss of tracking (eg cliffs above, bush/hills). obviously in a tunnel tracking will be compromised but after 100m it should be able to pickup again instantly

it seems to me that the basic core functionality of these devices is to track your route (and hence provide pace etc metrics) and its not unreasonable to expect that to be reliable to the point where you rarely if ever get noticeable error.

garmin are offering to replace my 935 but i'm not sure there is much point in replacing a basically brand new watch with another given that this does not seem to be a one-off bad unit.
a few possibilities occur to me:
- my expectations are unrealistic and this is just how gps tracking is
- i have really bad luck to get the same bad unit fault twice
- i'm doing something wrong... i don't know what
- garmin have a fundamental fault in their hardware or software across multiple generations of devices

i have never seen the same behavior from either my Edge 500 or Edge 820, including in the same locations

anyone seen similar behaviour or have other relevant expertise?
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Re: Garmin Forerunner GPS Tracking Issues [pk1] [ In reply to ]
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There are a number of things I'm irritated with Garmin about related to my FR920XT, but not GPS. It's been replaced once (altimeter), but other than that, it's been solid. No GPS dropouts where dropouts are not expected (tunnels, tall urban buildings, etc.). I don't notice any different performance at 100% battery vs 20% battery (not on the same day/course/ event - I'm a sprint distance kind of guy). Are the problems in the same physical location for both devices - i.e. something about the environment? When we lived in Lausanne, my Polar would report max HR (I dunno - 245 bpm or something) every time I cycled along a particular road that paralleled the (electric) train...
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Re: Garmin Forerunner GPS Tracking Issues [giorgitd] [ In reply to ]
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battery level has never appeared to be relevant.

3 different locations in the 3 main incidents i'm focusing on. one was near an airport, one near a shipping port and one near a sawmill which did all occur to me as possible interference sources but i don't see why and i have used both forerunner and edge units in these exact same areas many times without issue.
i'm familiar with the polar HR issues around HV electricity from past, fortunately that is one issue i have not seen with garmin

when you have seen dropouts due to tunnels, buildings etc, does it reliably come back promptly when you come out of that area?
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Re: Garmin Forerunner GPS Tracking Issues [pk1] [ In reply to ]
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Yes, pretty rapid recovery. I don't have many tunnels, but enjoy urban running especially when traveling. Big cities, tall buildings, bad GPS. But within a block away from buildings, spot on GPS tracks, IME.
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