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hzoi

GPS + GLONASS anomaly this weekend

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Had an odd occurrence with my Garmin Montana 610 this weekend.

 

I was driving down the highway near Richmond, Virginia, minding my own business, when I noticed the map had frozen. Restarted the GPSr and found that it refused to lock on to sats -- the sat status page would home in on more and more sats, then suddenly all would vanish and I got the "Lost satellite reception" error I normally only see in tunnels. We were on open road, no obstructions, sunny and blue skies.

 

Used the phone to get to our destination (no issues with reception there) and then started fiddling with settings. I had been using GPS + GLONASS since I got the unit months ago, with WAAS/EGNOS enabled. But on this occasion, the GPSr refused to lock in on sats until I set it to GPS only, plus WAAS/EGNOS.

 

Today I was able to get a lock with first just GPS and WAAS/EGNOS, then turned GPS + GLONASS back on and got a lock as well.

 

I'm chalking this up to a one-time anomaly, similar to the one time I went hiking and suddenly discovered that the GPSr thought I had magically teleported from southern New Mexico to the Gulf of Guinea (which lasted for about an hour before suddenly undoing itself). But I was curious as to whether anyone else had experienced this.

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"Gulf of Guinea", also known as Null Island, is special in electronic cartography as it's coordinates "0, 0" The intersection of the equator and the prime meridian is where you describe.

 

I'm doubtful that toggling GLONASS was actually involved. More likely, the passing of time while the unit was recovering from an internal crash or inconsistency was the "fix". It probably had a very confused idea of your location (corrupt time or saved location) and you had to wait for a cold start for "first fix".

 

If it happens again, I'd consider the unit slightly defective.

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One of my Montana units would suffer the same 'glitch', where I would be driving down the road along a highway (etc), and suddenly it would briefly show me at the 0, 0 coordinates, then return to my current location, all in a matter of seconds. Maybe a minute total. Never did determine why....

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I'm doubtful that toggling GLONASS was actually involved. More likely, the passing of time while the unit was recovering from an internal crash or inconsistency was the "fix". It probably had a very confused idea of your location (corrupt time or saved location) and you had to wait for a cold start for "first fix".

 

If it happens again, I'd consider the unit slightly defective.

I've actually seen the same problem on an Oregon 600 and Oregon 650, at different times about a year apart. The behavior was just like hzoi described: it would gradually lock onto more satellites for about a minute with the EPE also increasing until it got very high, and then they'd all disappear and you'd get the "Lost satellite reception" message. It would then restart the same process and keep going in a loop. In both cases, turning off GLONASS broke the loop and the device was able to start working normally. On my 600, I turned GLONASS back on about a week later and it worked as expected. The 650 is my caching partner's and she only just had the issue a little over a week ago, so we haven't tried turning GLONASS back on yet. We'll try that on Saturday.

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I'm doubtful that toggling GLONASS was actually involved. More likely, the passing of time while the unit was recovering from an internal crash or inconsistency was the "fix". It probably had a very confused idea of your location (corrupt time or saved location) and you had to wait for a cold start for "first fix".

 

If it happens again, I'd consider the unit slightly defective.

I've actually seen the same problem on an Oregon 600 and Oregon 650, at different times about a year apart. The behavior was just like hzoi described: it would gradually lock onto more satellites for about a minute with the EPE also increasing until it got very high, and then they'd all disappear and you'd get the "Lost satellite reception" message. It would then restart the same process and keep going in a loop. In both cases, turning off GLONASS broke the loop and the device was able to start working normally. On my 600, I turned GLONASS back on about a week later and it worked as expected. The 650 is my caching partner's and she only just had the issue a little over a week ago, so we haven't tried turning GLONASS back on yet. We'll try that on Saturday.

Had GPS + GLONASS back on today while I was out on a trail, as well as car nav - no issues.

 

Glad I'm not the only one, that this isn't permanent, and that giving GLONASS a rest seems to address it. I guess the question is whether it's a Garmin issue or a GLONASS issue, but I doubt either one would be interested in disclosing it.

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