Will a magnetic mount screw up a GPS?

[spagthorpe]

I don't know if this is a stupid question or not, I've never seen anything on it. I was thinking of using a basic mount with a couple of strong magnets on it to mount a GPS V to a motorcycle. Is there anything in a GPS that would get screwed up?

[jvavrus2000]

There shouldn't be anything in a basic GPS system that a magnet will affect. Your handheld GPS unit should work fine in any reasonable magnetic field. Having said that there are a few caveats...

 

Units with electronic compasses will probably point at (or away from?) the magnets, not North.

 

Some high end vehicle navigation units (and maybe others???) use disk drives and/or CD/DVD drives for map storage. These devices will not like magnets....

[spagthorpe]

Well, I thought I would be bold, and called Garmin Tech Support. The answer I got was basically "I don't think so", so they don't seem to have any idea either. I guess I'll build a mount, and see what happens, maybe try it out on a known course, and see if it screws anything up.

[Morseman]

quote:

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Originally posted by spagthorpe:

I don't know if this is a stupid question or not, I've never seen anything on it. I was thinking of using a basic mount with a couple of strong magnets on it to mount a GPS V to a motorcycle. Is there anything in a GPS that would get screwed up?

---

 

Nope!

 

Radio waves (which are what GPS receivers use) are not affected. Even the compass on the GPS will be unaffected, as it takes its data from the received signals from the Sats.

 

However, if you use a "normal" compass, it will be affected by the magnet.

 

Don't let people, who don't understand radio wave theory, tell you that it will affect the 'magnetic' component of an E/H wave. It wont. :-)

 

To test this, hold a magnet near the antenna of your VHF radio (VHF = MHz, GPS =GHz signals). There will be no difference in signal received.

 

If, however, you put your magnet near the loudspeaker (which uses a large permanent magnet and coil to make the sound you hear) there will be an effect.

 

The thing to realise is, you don't have a loudspeaker on your GPS receiver. Well, not one that alters the display of where you are. ;-)

 

--... ...--

Morseman

[+Alan2]

quote:

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Originally posted by Morseman:

... Even the compass on the GPS will be unaffected, as it takes its data from the received signals from the Sats.

 

However, if you use a "normal" compass, it will be affected by the magnet.

 

Morseman

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The compasses in the Vista and Platinum are "normal" compasses that don't require sats so it seems to me you would screw up the compass direction with these unit if used near magnets. The only time you wouldn't would be when you are driving and the direction switches to the sats. Problem is would the magnets permenantly effect the accuracy of the built-in magnetic compass when you use in the bush??

 

A question better minds then mind will have to answer as I'm still trying to understand why opposite poles attract and similars repel!!

 

Alan

[Kerry.]

Many of the external antenna's have magnetic mount base options and there's no problems with them and it's the antenna and/or signal that would be subject to any magnetic effect if it existed.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

Many of the external antenna's have magnetic mount base options and there's no problems with them and it's the antenna and/or signal that would be subject to any magnetic effect if it existed.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+st_richardson]

quote:

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Originally posted by spagthorpe:

...I was thinking of using a basic mount with a couple of strong magnets on it to mount a GPS V to a motorcycle. Is there anything in a GPS that would get screwed up?

---

 

As others have said, the magnet is likely to influence an electronic compass but not a GPS direction reading. BTW... The metal of the bike is likely to influence an electronic compass also.

 

I'd be more concerned as vibration. Make sure its firmly attached if you deside to off road.

[+st_richardson]

quote:

---

Originally posted by spagthorpe:

...I was thinking of using a basic mount with a couple of strong magnets on it to mount a GPS V to a motorcycle. Is there anything in a GPS that would get screwed up?

---

 

As others have said, the magnet is likely to influence an electronic compass but not a GPS direction reading. BTW... The metal of the bike is likely to influence an electronic compass also.

 

I'd be more concerned as vibration. Make sure its firmly attached if you deside to off road.

[Couch_Potato]

quote:

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Originally posted by Alan2:

 

The compasses in the Vista and Platinum are "normal" compasses that don't require sats so it seems to me you would screw up the compass direction with these unit if used near magnets.

Alan

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The compasses in the Vsta and Plainum are not 'normal'. They are elecronic cmpasses which can be calibrated to minimize interfence from local external magetic fieds. I think the procedure of calibration is just to turn around in a couple of complete circles, i.e. more than 720º.

 

However, once you remove the unit from the magnetic base it would need to be recalibrated to work in the absence of the field from the base.

 

These are my opinions and may have nothing to do with the actual facts.

 

Mike

 

I'm not lost!

I just don't know where I am.

[Couch_Potato]

quote:

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Originally posted by Alan2:

 

The compasses in the Vista and Platinum are "normal" compasses that don't require sats so it seems to me you would screw up the compass direction with these unit if used near magnets.

Alan

---

 

The compasses in the Vsta and Plainum are not 'normal'. They are elecronic cmpasses which can be calibrated to minimize interfence from local external magetic fieds. I think the procedure of calibration is just to turn around in a couple of complete circles, i.e. more than 720º.

 

However, once you remove the unit from the magnetic base it would need to be recalibrated to work in the absence of the field from the base.

 

These are my opinions and may have nothing to do with the actual facts.

 

Mike

 

I'm not lost!

I just don't know where I am.

[+Alan2]

quote:

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Originally posted by mvwood:

Originally posted by Alan2:

 

The compasses in the Vista and Platinum are "normal" compasses that don't require sats so it seems to me you would screw up the compass direction with these unit if used near magnets.

Alan

---

 

The compasses in the Vsta and Plainum are not 'normal'. They are elecronic cmpasses which can be calibrated to minimize interfence from local external magetic fieds. I think the procedure of calibration is just to turn around in a couple of complete circles, i.e. more than 720º.

 

QUOTE]

 

Mike: This is just my opinion too and might not be the facts, but while it's true you can adjust out surrounding influences like ferrous metal, I don't think that would overcome strong magnets holding the GPS the original question.

 

My 2 cents. I'm stillwondering if the strong magnets though could permenantly effect the calibration??

 

Alan

[+apersson850]

First, the "compass" derived from the GPS satellites, and computed from observing the direction of movement, isn't affected by any magnet.

However, some units, like the Garmin Vista and GPS 76S (Got any yet, Hawkeye? ) have magnetic compasses too. Any normal magnetic compass will be completely confused by a magnet nearby. But these GPS units don't have a conventional magnetic needle spinning around in there. Instead, they use something called a fluxgate compass.

Since the fluxgate principle, as far as I've understood it, is based upon almost saturating coils, and then measuring the difference the earth's magnetic field causes, it could be that it works with a magnet nearby, as long as that magnet doesn't change its position, relative to the compass. The unit has to be calibrated with the magnet in place, of course. But it could also be that a strong magnet nearby may make it impossible to calibrate, since the current required to saturate the coils may be outside the possible range.

 

The varying magnetic field caused by varying electric current in the wiring of a vehicle, be it a car or motorbike, is probably a larger problem. Since it varies, it can't be calibrated away. Besides, not all units have a three-dimensional fluxgate, but require the unit to be horisontal for the compass to work.

 

The fluxgate principle was discovered around 1910-1920 or so. The first application I know about was airborne systems, used to detect submerged submarines in the sea during World War II. Since a large piece of steel, like the sub, made an influence on the geomagnetic field, this anomaly could be detected by flying over the sub.

 

 

Anders

[+apersson850]

First, the "compass" derived from the GPS satellites, and computed from observing the direction of movement, isn't affected by any magnet.

However, some units, like the Garmin Vista and GPS 76S (Got any yet, Hawkeye? ) have magnetic compasses too. Any normal magnetic compass will be completely confused by a magnet nearby. But these GPS units don't have a conventional magnetic needle spinning around in there. Instead, they use something called a fluxgate compass.

Since the fluxgate principle, as far as I've understood it, is based upon almost saturating coils, and then measuring the difference the earth's magnetic field causes, it could be that it works with a magnet nearby, as long as that magnet doesn't change its position, relative to the compass. The unit has to be calibrated with the magnet in place, of course. But it could also be that a strong magnet nearby may make it impossible to calibrate, since the current required to saturate the coils may be outside the possible range.

 

The varying magnetic field caused by varying electric current in the wiring of a vehicle, be it a car or motorbike, is probably a larger problem. Since it varies, it can't be calibrated away. Besides, not all units have a three-dimensional fluxgate, but require the unit to be horisontal for the compass to work.

 

The fluxgate principle was discovered around 1910-1920 or so. The first application I know about was airborne systems, used to detect submerged submarines in the sea during World War II. Since a large piece of steel, like the sub, made an influence on the geomagnetic field, this anomaly could be detected by flying over the sub.

 

 

Anders

[ecbaatz]

Why not just get a Ram mount. I use them in the car on my bicycle and on my quad. Very durable, easy to use and not that expensive.

 

Just a thought.

[+apersson850]

Or, if you are in a hurry or on a low budget, chew a chewing gum for a while, then use that to glue your GPS to whatever.

 

"I've actually seen this done..."

 

Anders

[John E Cache]

quote:

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Originally posted by Anders:

snip But these GPS units don't have a conventional magnetic needle spinning around in there. Instead, they use something called a fluxgate compass.

Since the fluxgate principle, as far as I've understood it, is based upon almost saturating coils, and then measuring the difference the earth's magnetic field causes, it could be that it works with a magnet nearby, as long as that magnet doesn't change its position, relative to the compass. The unit has to be calibrated with the magnet in place, of course. But it could also be that a strong magnet nearby may make it impossible to calibrate, since the current required to saturate the coils may be outside the possible range.

snip

http://img.Groundspeak.com/user/avatar/24148_200.jpg

 

Anders

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Wouldn't Hall Effect be cheaper because you already have a semi-conductor chip?

 

What kind of coils saturate? The coils I have seen are linear.

 

I think I read that the Platinum has an electronic bubble display that tells you when it is level. Is that why it needs a 3 axis sensor? I thought you only needed two axis to do NS and EW.