GPS won't lock.

[Neil]

All of a sudden my gps is unable to get a lock onto even a single satellite even though I had been using it in the same location 2 days earlier.
I e-mailed Garmin and this is the very prompt reply I received.

Satellite acquisition can be interrupted by many factors. Please attempt
the following. From the Main Menu highlight and select the Satellite
option. Here, highlight the soft key in the top right of your screen that
looks like a single page. Choose this option and then New Location. After
New Location choose Automatic. Once this has been done allow for the device
to set in an open sky view for no less than 20 minutes. This will allow the
unit to select new satellites and begin to give you navigation data.

I will try this out this evening. In the meanwhile, any comments?

 

[Artex]

I may be going out on a limb here, but I wonder if sunspot activity is the culprit. I just got done running, and my Forerunner GPS gave me "weak GPS signal" readings several times more than normal. I'm not sure how much weather plays a factor, but there wasn't a cloud in the sky.

 

[Pucknuts61]

Hi Neil,
I know that you, Dougpaul, and Bob&geri, are probably the most proficient users of GPS and the most knowledgable but I'll throw my experience in on this one in hopes it might be this simple.
When mine wouldn't lock I found that it was my batteries. A quick change to some new lithiums and I was set.
The only other time I had this problem was in a valley so I could only get 1 or 2 satelites from overhead and none of the horizontal ones. The GPS could never triangulate correctly until I got a little higher.
Hope this helps,
Bill

 

[SAR-EMT40]

I did a check and the USNO isn't reporting any problems with the sats. I would just chalk it up to the sats may not have been in a good orientation to get a lock last time or the you couldn't see enough of them. That of course is assumming that resetting it and after 20 minutes or so you get a lock this time. My unit (my cheap, old 12Xl) isn't having any problems. I haven't tested my vista C but I don't doubt that it is OK.

I have had similar things happen in the past. Sometimes I could explain it (sat problem) and other times I couldn't.

Let us know what happens.
Keith

 

[DougPaul]

Neil,
Just did a check (1:30pm) from the top floor (2 story, wood frame house, antennas and wires in the attic which can degrade signals)--got a good 6 sat fix (better than usual).

I presume you were looking at the satelliite page--it is the best source of information about what is happening with the satellites/signals.

(Packnuts61:
A bad constellation will not interfere with satellite reception. It only means that you cannot compute a meaningful fix from the available data.)

Garmin's instructions are just generic "no prior information" start instructions. This will correct a bad almanac (coarse orbits), bad clock, and bad initial location. But even with bad initial info, you are likely to get at least one sat.

All sorts of possible reasons for not getting even 1 sat: Bad batts, local interference, blocked signals, defective GPS, water in the GPS, incompetent operator (you are probably safe on this one), etc.

Certainly, check or replace the batts. (At least some of the Garmins can be booted into a diagnostic screen which shows the battery voltage. Hold down "enter" (or press the click stick) and "power on", for the eTrex Vista and 60CS. Probably the same for some other models.)

When you make your next try, just try it normally before trying Garmin's instructions. Perhaps it will work. (However, given that you had problems once, it might still be worth following Garmin's instructions to guarantee that you get a good almanac.)

Let us know what happens.

Doug

 

[Quietman]

If you look at the attached link, sun spot activity and solar radiation has been quite high the last few days. This can cause satellite issues.

Solar radiation

 

[Remix]

Leave it out it in an open area for 2-3 hours..maybe the almanac got corrupted and it needs to acquire a new one.

 

[DougPaul]

Leave it out it in an open area for 2-3 hours..maybe the almanac got corrupted and it needs to acquire a new one.

IIRC, it takes about 20 min to receive the almanac under good signal conditions. Longer won't hurt. All satellites transmit the same almanac covering all of the GPS satellites.

If you are trying to find the WAAS satellites, it may take several hours the first time. Once you get it, it will transmit its own almanac and will be much easier to find next time. (Garmin shows the WAAS satellite on the northern horizion until it gets the almanac.)

Doug

 

[DougPaul]

If you look at the attached link, sun spot activity and solar radiation has been quite high the last few days. This can cause satellite issues.

High solar radiation isn't likley to shut down the GPS, but it is likely to decrease the accuracy of the fixes. The transit time through the ionosphere becomes less predictable.

Dual frequency GPSes can estimate the ionospheric delay by looking at the difference between the signal arrival times at the two frequencies and are therefore less affected. The military has it now, in the works for civilians.

The GPS satellites are radiation hardened. (They are a military system, after all.)

Doug

 

[Neil]

All is well. I ended up following the instructions from Garmin as posted above and got a sat fix with that. Who knows what went wrong. I'm glad to know of this feature now. BTW what does the info on the diagnosis bootup mean?

 

[DougPaul]

All is well. I ended up following the instructions from Garmin as posted above and got a sat fix with that. Who knows what went wrong. I'm glad to know of this feature now. BTW what does the info on the diagnosis bootup mean?

Did you try getting a fix before using the Garmin "no info" procedure?

I only understand some of the fields on the diagostic screen. Some are obvious, some not. (Don't even recall what model GPS you have, and unless is the same as mine, I wouldn't know what it displays.)

Glad it works...

Doug

 

[Neil]

Did you try getting a fix before using the Garmin "no info" procedure?

I tried first with the rechargeable batteries that were in the unit then changed over to Duracells and left it out in the open for 15 minutes with no acquisition. Then I tried the Garmin procedure and got a fix. I put the rechargeable batteries back in and got a fix immediately under a big maple tree in my back yard. Thanks everyone for your input.

-Neil

 

[DougPaul]

I tried first with the rechargeable batteries that were in the unit then changed over to Duracells and left it out in the open for 15 minutes with no acquisition. Then I tried the Garmin procedure and got a fix. I put the rechargeable batteries back in and got a fix immediately under a big maple tree in my back yard. Thanks everyone for your input.

OK. Sounds like the unit had some bad data in it that needed purging.

Doug

 

[Rick]

...Then I tried the Garmin procedure and got a fix....
-Neil

I must be off on a limb somewhere. This is the normal procedure that I use whenever I travel more than a couple of hundred miles from home and then turn on my GPS. I thought this was the standard procedure to pick up a signal faster, if you are not near where you last used the GPS.
Do most just turn on their GPS if they are far from their home base and just wait for the signal to acquire and not use the new location feature??
Meaning I am simply taking an unneccesary step to acquire in a new location?
Thanks,
Rick

 

[Neil]

Until now I was ignorant of the procedure. I would just turn the unit on and go. In May I was near the Ontario-Manitoba border. (North of Minnesota). I switched the gps on and got a fix just like that (snaps fingers). Same thing when I got back home.
This am. I turned it on and tried using the new location function but it was greyed out so the gps knows I haven't changed location since yesterday.
I wonder what else it knows?

 

[Rik]

Glad it's working. I was worried about you finding your way home yesterday!

 

[DougPaul]

I must be off on a limb somewhere. This is the normal procedure that I use whenever I travel more than a couple of hundred miles from home and then turn on my GPS. I thought this was the standard procedure to pick up a signal faster, if you are not near where you last used the GPS.
Do most just turn on their GPS if they are far from their home base and just wait for the signal to acquire and not use the new location feature??
Meaning I am simply taking an unneccesary step to acquire in a new location?

You can do either. If you just turn it on, it will soon realize that it has moved and start a wider search.

There are three pieces of prior information used to perform a cold start: approximate time, approximate location, and almanac (coarse orbital info used to help locate the sats). The only thing you want to invalidate is the location if you have moved a significant distance--but as noted above, the unit will do it for you after a short period.

Doug