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GPS "Compass" Anomaly


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I'm the OP.

 

None of the replies were particularly helpful.

 

In 3 years, I've never before had this happen. I should be able to start walking in the direction of the pointer and, if I'm walking in a strength line, come somewhat close to GZ. It has alawys been like this in the desert. Here the straight line would have put me 100 to 150 feet off.

 

I'm ok with the idea that when I get close, the arrow does not help much. But, I should not have been walking giant "J" shapes in the open desert.

Now, any good explanations?

I was very interested in your issues and compared your Garmin GPS experiences with my Delorme GPS experiences over the last few years. But I was not interested enough to go out and buy a handheld Garmin for a test. I might however drive over to the Mojave Desert just for the memories of that being the first trip I took with my then new Magellan GPS over 15 years ago. I pulled off the highway and drove the car back and forth in a Rest Stop just to compare the GPS compass with a magnetic one with a suction cup mount.

 

Then two days later, I bought a "real" car compass with adjustable magnetic compensation screws as well as a suction cup.

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I'm the OP.

 

None of the replies were particularly helpful.

 

In 3 years, I've never before had this happen. I should be able to start walking in the direction of the pointer and, if I'm walking in a strength line, come somewhat close to GZ. It has alawys been like this in the desert. Here the straight line would have put me 100 to 150 feet off.

 

I'm ok with the idea that when I get close, the arrow does not help much. But, I should not have been walking giant "J" shapes in the open desert.

Now, any good explanations?

 

I just realized that I was also walking geoart in the Mojave on the same day about 100 miles S/W of you. While I wasn't walking "J" shapes, I pretty much could have if I wasn't constantly adjusting. Instead, I was walking in big arcs as the direction that I started in was constantly having to be adjusted. If I had continued in the exact direction that I started, I could have easily been 100'-200' off. I didn't make much of it as I had never done this type of caching before, when you set the next waypoint and walk cross country directly to it. I'm usually on winding trails and the needle is never pointing directly to the cache.

 

Who knows? Maybe it's mineral deposits in the ground?

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I'm the OP.

 

None of the replies were particularly helpful.

 

In 3 years, I've never before had this happen. I should be able to start walking in the direction of the pointer and, if I'm walking in a strength line, come somewhat close to GZ. It has alawys been like this in the desert. Here the straight line would have put me 100 to 150 feet off.

 

I'm ok with the idea that when I get close, the arrow does not help much. But, I should not have been walking giant "J" shapes in the open desert.

Now, any good explanations?

 

I just realized that I was also walking geoart in the Mojave on the same day about 100 miles S/W of you. While I wasn't walking "J" shapes, I pretty much could have if I wasn't constantly adjusting. Instead, I was walking in big arcs as the direction that I started in was constantly having to be adjusted. If I had continued in the exact direction that I started, I could have easily been 100'-200' off. I didn't make much of it as I had never done this type of caching before, when you set the next waypoint and walk cross country directly to it. I'm usually on winding trails and the needle is never pointing directly to the cache.

 

Who knows? Maybe it's mineral deposits in the ground?

 

I've cached in all types of terrain ( Mojave, swamps, etc)using several 3-axis GPS units and its not unusual for the unit to be " correcting " as you're walking.....as you say, sort of a big arc.

I'm not sure what causes these corrections but I end up at GZ.

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I have had units with 3 axis electronic compasses and units without. Compass alignment in a GPSr is something that I stopped worrying about when I realized that all I need do is line sun (or moon) on the GPS' compass rose with the actual sun (or moon). Once that is done, the GPS pointer will point at the cache even when you aren't moving.

 

Of course, I always carry a real compass when I'm caching, too. I take the 'bearing to target' from the GPSr and then simply rotate the compass' dial until number on the face lines up with the arrow on the base. Align the compass' arrow with North on the face, and the compass now points towards the cache.

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