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Why does this happen


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I'd like to know if anyone can explain this phenomenon to me. Its happend fairly regularly, so I assume its common behavior.

 

I'm using an Garmin etrex Vista HCX. When I switch to arrow pointer mode, half the time the arrow points in the opposite direction from the cache location. In these circumstances I follow the declining distance to target and usually get on the cache fairly handily. Any idea why this would happen? To me it seems that since the distance is counting down correctly and since the unit is using the same data for distance and bearing they would both agree.

 

Not sure if it matters but I've never calibrated the compass.

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The Vista's have a 2-axis compass and have to be held perfectly level for the compass to work properly when you're not moving..

 

Unlike the 60 series (which also has just a 2-axis compass) the Vista won't actually warn you that you're not holding it level, the compass just reads wonky :blink:

 

Maybe that's your observation?

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Not sure if it matters but I've never calibrated the compass.

That would be a first good step. Do you ever get the "Hold Level" warning?:

1278473298.jpg

If so, when navigating you need to hold the unit level just like a real compass (ok, so my compass has a clinometer so I don't always hold it level). What maps do you have installed? Is "Lock on Road" enabled? Is your routing Guidance Method preference set to "Follow Road" or "Off Road"? Could be a combination of a couple of things...

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You need to calibrate it every time you change batteries.

that's not really true, at least not for all GPS devices. i've calibrated the compass on my oregon 450 once and never had to recalibrate since, and i'm using regular NiMH batteries which are a couple of years old.

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You need to calibrate it every time you change batteries.

that's not really true, at least not for all GPS devices. i've calibrated the compass on my oregon 450 once and never had to recalibrate since, and i'm using regular NiMH batteries which are a couple of years old.

 

For the Vista it is, and I own both the original and the HCx.

 

Page 28

http://www8.garmin.com/manuals/eTrexLegend...wnersManual.pdf

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Not sure if it matters but I've never calibrated the compass.

 

It matters a lot. Calibrate it and your problem should disappear. You need to calibrate it every time you change batteries.

I keep hearing that, and by the time you change, it's usually too late. The compass chip is voltage sensitive. I've only found two ways to keep the compass happy -- either change cells before they are discharged significantly, or use the NiZn cells with the dead flat discharge curve (still very happy with those, BTW).

 

When the charge on the cells drops, the calibration will be off. If you calibrate with cells that have been discharged some, then swap in fresh ones, the calibration will be off.

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You need to calibrate it every time you change batteries.

that's not really true, at least not for all GPS devices. i've calibrated the compass on my oregon 450 once and never had to recalibrate since, and i'm using regular NiMH batteries which are a couple of years old.

 

For the Vista it is, and I own both the original and the HCx.

 

Page 28

http://www8.garmin.com/manuals/eTrexLegend...wnersManual.pdf

 

I had never had this problem with my CSx until last weekend. a recalibration seemed to help for a bit but then it would point the wrong direction a short time later. I finally changed the batteries and the problem went away.

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Now look what I started!!!

 

1. I'll remove my watch next time and see what happens

2. I'll calibrate next time I swap batteries and see what happens

3. Checked this AM. there is no "hold level" message on the screen. tried holding both horizontal(correct) and vertical(incorrect) no complaints from the GPS.

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Now look what I started!!!

 

1. I'll remove my watch next time and see what happens

2. I'll calibrate next time I swap batteries and see what happens

3. Checked this AM. there is no "hold level" message on the screen. tried holding both horizontal(correct) and vertical(incorrect) no complaints from the GPS.

 

You need to recalibrate now and you might even benefit from letting the gps 'bake' under open sky for a half hour so the almanac can update. (just in case)

 

You won't get a hold level message but point it about 10 o'clock assuming the horizon at 9 and you'll do fine.

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Update: took the watch off after I found the cache, it seemed to swing the pointer a few degrees closer to the correct heading. Who woulda thought. I always assumed the compass was getting its heading off the GPS signals. Guess not.
Actually, you can configure it to do exactly that (not use the electronic compass), but you won't get any useful information unless you're moving - without the electronic compass, it has no way to know which way you're holding the unit.
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You need to calibrate it every time you change batteries.

that's not really true, at least not for all GPS devices. i've calibrated the compass on my oregon 450 once and never had to recalibrate since, and i'm using regular NiMH batteries which are a couple of years old.

Then why does the manual for the Oregon 450 tell you recalibrate after changing batteries? Just because you haven't been doing something, doesn't mean shouldn't be doing it.

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I've seen this question many times here and usually the same answer.

 

This also happens with my 60Cx and with the prior 60Cx which didn't survive a fall fro the truck at highway speed. No compass to calibrate. Turns to what appears to be 180° when I get ~100' from GZ. I just try to keep the same bearing & watch the distance count down...

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