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Can metal in your body effect GPS units?


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OK, I'm sort of joking here, but really wondering at the same time.

 

DH & I have 2 identical Garmin GPSmap 60cs units. They have same firmware upgrades. All settings the same. Calibrated the same at same time & place.

 

I have an 11" metal rod connected to my spine - attached with wingnuts. :laughing: I hold my GPS in my hand at about stomach height & somewhat close to my stomach.

 

It seems to never fail, that my GPS's arrow will always want to point back towards my stomach. While DH's says we need to head in another direction.

 

We'll trade GPS...and "mine" that he is now using will now point to the right direction; and "his" that I'm now using will point to my stomach. It's become somewhat of a joke, that I've eaten the cache. LOL

 

But seriously, can metal in a body (plates, pins, rods....) effect a GPS? I don't set off airport detectors even though I have more metal than my mom. She sets off detectors & she only has wires from a triple by-pass.

 

I THINK my rod is stainless steel if that helps.

 

Anyone else have this strange effect with GPS units. :laughing:

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I would imagine that the metal in your body is either stainless steel or titanium and neither should have a effect on your gps as both are non-ferrous. If you have a pacemaker or the like this certainly can effect the compass. In order for even iron to make the compass point to your body it would have to be magnetized. Maybe you have eaten a small magnet or the aliens have implanted a tracking device in you :laughing:

 

HummerH1

OK, I'm sort of joking here, but really wondering at the same time.

 

DH & I have 2 identical Garmin GPSmap 60cs units. They have same firmware upgrades. All settings the same. Calibrated the same at same time & place.

 

I have an 11" metal rod connected to my spine - attached with wingnuts. :unsure: I hold my GPS in my hand at about stomach height & somewhat close to my stomach.

 

It seems to never fail, that my GPS's arrow will always want to point back towards my stomach. While DH's says we need to head in another direction.

 

We'll trade GPS...and "mine" that he is now using will now point to the right direction; and "his" that I'm now using will point to my stomach. It's become somewhat of a joke, that I've eaten the cache. LOL

 

But seriously, can metal in a body (plates, pins, rods....) effect a GPS? I don't set off airport detectors even though I have more metal than my mom. She sets off detectors & she only has wires from a triple by-pass.

 

I THINK my rod is stainless steel if that helps.

 

Anyone else have this strange effect with GPS units. :laughing:

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Nope, no pacemaker. And if I swallowed a magnet, I sure hope it would have come out by now. :laughing: We noticed this anomoly about a year ago. Before that we only had 1 GPS, & DH was the one who mainly carried it.

 

This rod was put in 25 yrs ago. I've had several x-rays since then where my rod is visible. I actually have a set here at home taken 2 yrs ago. There doesn't appear to be any other foreign objects in me. lol

 

Aliens is a possiblity however. :laughing:

 

Really, I wonder if this happens to anyone else.

Edited by wandering4cache
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I would imagine that the metal in your body is either stainless steel or titanium and neither should have a effect on your gps as both are non-ferrous.

Um, stainless steel is always ferrous, since it is mostly iron!

 

Some stainless steels are non-magnetic; however, others can have a significant magnetic field, especially after cold-working.

 

If I were the OP, I would turn off the magnetic compass in the GPS (if it's possible) and see if the behavior changes.

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I contacted the techie at our local Magellan agency and he also confirmed that it would only be the compass that could be affected by metal body parts, and only if they exhibit a certain amount of magnetism themselves. The magnetic force would be minimal to cause a problem with compass readings.

 

Metal parts should NOT cause any anomolies with satellite reception.

 

The techies I spoke to are very intrigued by this question and have offered to find out more information.

 

I'll keep you informed.

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Holding the GPS too close to your body can block the GPS signals, since liquid water blocks them, and there is a considerable amount of salt water in your body. The stainless rod could have a magnetic field, but I know from personal experience, mostly in the military, that any ferrous metal, magnetized or not, will affect a compass. Having your rifle near the compass will cause error, as will any other iron you have around. It's easy to see the effect, by bringing an iron object close to a compass. That's why compasses have to be calibrated to be accurate. Put a compass in your car, and it will not point to north, most likely. You have to adjust the compensation screws, to move them closer or further away, to compensate for the metal in the car. Whether your rod is actually affecting the compass is hard to say, but it's easy enough to put the compass somewhere, have someone see what it reads, and then come up close to it and see if the needle moves.

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Could it be that the big bag of water that is your body is affecting sat lock?

 

I CERTAINLY hope that wasn't a shot at my size or weight. ???

 

Good info from everyone else.

It certainly wasn't, since I have no idea what your size or weight is.

 

However, the way you are holding your GPSr may cause interference with sat signals (since you are mostly made out of water). This could be resulting in your accuracy issues.

 

BTW, the rod and screws in my back do not appear to affect my GPSr or compass.

Edited by sbell111
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Could it be that the big bag of water that is your body is affecting sat lock?

 

I CERTAINLY hope that wasn't a shot at my size or weight. ???

 

Good info from everyone else.

It certainly wasn't, since I have no idea what your size or weight is.

 

However, the way you are holding your GPSr may cause interference with sat signals (since you are mostly made out of water). This could be resulting in your accuracy issues.

 

ok then. yes, we've played around with me holding arm out as far as possible. Can't remember results though since we've always just been joking around about this. I never really thought there could be some truth to it all.

 

Next time we go out, I hope to conduct some better "scientific" tests. :D

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When we are caching there are days when we have to hand off the GPSr to the other person to get accuracy. I agree that it's strange how two people can hold it and get consistently different readings from the same spot. (Incidentally, my wife cannot wear a watch because something in her body kills the battery very quickly.)

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I would imagine that the metal in your body is either stainless steel or titanium and neither should have a effect on your gps as both are non-ferrous.

Um, stainless steel is always ferrous, since it is mostly iron!

 

Some stainless steels are non-magnetic; however, others can have a significant magnetic field, especially after cold-working.

 

If I were the OP, I would turn off the magnetic compass in the GPS (if it's possible) and see if the behavior changes.

I suspect Surgical Stainless Steel is non magnetic. Else MRI's would be a problem.

 

As for the GPS itselef, I suspect the water in a persons body has more impact.

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Interesting comments about water content.

 

I wonder if this could be related to the body's conductivity. We were fooling around with a digital multimeter the other day, and several individuals took turns holding the probes with the meter set to resistance.

 

My resistance (holding a probe in each hand between forefinger and thumb) was a tad over 5 megohms.

 

Male 1 = 1.3 meg

Male 2 = 1.7 meg

Male 3 = 3.1 meg

Female = 130 kilo ohms! VERY low!

 

I found this to be fascinating - why such a vast difference. (I checked mine again - still very high)

 

So ...... if the body has a low resistance, there is an easier elctrical path to earth (ground), which, electrically speaking, means that the body is acting as a "grounded vertical conductor" which could cause the signals to weakened. Maybe!

 

Another weird observation ...... the older the test subject the higher the resistance. Now this is getting totally "X-Files"!

 

This is an interesting thread. I would love to get to the bottom of this one ......

Edited by Grawp
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Interesting comments about water content.

 

I wonder if this could be related to the body's conductivity. We were fooling around with a digital multimeter the other day, and several individuals took turns holding the probes with the meter set to resistance.

 

My resistance (holding a probe in each hand between forefinger and thumb) was a tad over 5 megohms.

 

Male 1 = 1.3 meg

Male 2 = 1.7 meg

Male 3 = 3.1 meg

Female = 130 kilo ohms! VERY low!

 

I found this to be fascinating - why such a vast difference. (I checked mine again - still very high)

 

So ...... if the body has a low resistance, there is an easier elctrical path to earth (ground), which, electrically speaking, means that the body is acting as a "grounded vertical conductor" which could cause the signals to weakened. Maybe!

 

Another weird observation ...... the older the test subject the higher the resistance. Now this is getting totally "X-Files"!

 

This is an interesting thread. I would love to get to the bottom of this one ......

Speakng as a scientist, a former electronics engineer, and a former ham radio operator, much of this can be explained... Here is my stab at it:

 

In general, the skin resistance measured for a person will vary across gender, with males, in general, tending to exhibit greater skin resistance than females in the same age range and of the same general health and hydration status. This is due simply to the fact that males -- due to across-sex differences dictated by genetics -- tend to have thicker skin and a thicker layer of dead skin cells in the outer layers of the skin; this introduces more resistance to the flow of current. Health and hydration levels will also affect skin resistance, and the better hydrated a person is -- and this depends not only upon water intake but upon general health status and particularly levels of major minerals and trace elements -- the more conductive their layers of skin will be, and thus, the better hydrated a person is, the lower will be their skin resistance. Lastly, skin resistance will, in general, with a few exceptions, tend to rise with age, due to gradual decline (on average) in hydration levels and due to slow and gradual shifts in health status, including circulatory status. Lastly, aging of the skin will -- due to oxidative-damage induced crosslinking and gradual accumulation over time of autoxidative glycosylation end products (AGE products) -- tend to cause a to gradual increase in observed skin resistance, and so, in general, an older person will exhibit a higher skin resistance than a younger person for all of the above-listed reasons.

 

Lastly, states of tension versus relaxation will also affect skin conductivity. When you are in a very relaxed state, your skin resistance will be much lower than when you are feeling stressed or tense. This is because there is greater blood flow to the skin and extremities during states of relaxation, versus lesser flow, and hence conconitant lesser conductivity of tissues, during times of autonomic nervous system arousal (aka autonomic arousal, known as "tension" in the popular vernacular.)

 

As for the effects of the body upon radio frequency (RF) signals at the frequencies used by the GPS system: In general, the body, due to its conductivity and concomitant shielding effects, will tend to block such RF signals quite strongly, and the greater the levels of hydration, the greater will be the degree of blocking of those signals. The presence of the aforementioned Harrington rod in the spine will only tend to increase the attenuation of signals by the body even more. Due largely to the factor of partial blocking/attenuation of such RF signals by the body, I tend, particularly when in areas of poor reception (such as dense forest cover), to hold the GPSr out from my body and at chin height or higher, to allow its antenna a more unobstructed view of the sky at the frequencies of interest.

Edited by Vinny & Sue Team
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It seems to never fail, that my GPS's arrow will always want to point back towards my stomach. While DH's says we need to head in another direction.

To find out for sure, hold the GPS like normal and see if it's pointing towards your stomach like you say. If so, have DH hold it in the same place (near your stomach, with your arms at your side) and see what happens. If it's no longer pointing towards your stomach then maybe it's your watch?

 

If it is pointing towards your stomach, have DH walk around you. If he gets around to your back and he arrow is pointing towards you the entire time, then maybe it's the rod in your back. If it's pointing away from you, maybe not.

 

Then turn and face the opposite direction and do it all again. If the arrow points towards your stomach, and away from your back (in the opposite direction from the first test) then again, maybe the rod does have a strong magnetic field.

 

Either way, you should be able to figure out if it's just you or not.

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It seems to never fail, that my GPS's arrow will always want to point back towards my stomach. While DH's says we need to head in another direction.

To find out for sure, hold the GPS like normal and see if it's pointing towards your stomach like you say. If so, have DH hold it in the same place (near your stomach, with your arms at your side) and see what happens. If it's no longer pointing towards your stomach then maybe it's your watch?

 

If it is pointing towards your stomach, have DH walk around you. If he gets around to your back and he arrow is pointing towards you the entire time, then maybe it's the rod in your back. If it's pointing away from you, maybe not.

 

Then turn and face the opposite direction and do it all again. If the arrow points towards your stomach, and away from your back (in the opposite direction from the first test) then again, maybe the rod does have a strong magnetic field.

 

Either way, you should be able to figure out if it's just you or not.

I support Mushtang's suggestions as an excellent way of performing some additonal diagnostics and troubleshooting regarding the GPSr arrow pointing toward your (the OP's) stomach. And, there seem to be some people around whom electronic equipment operates very oddly; have you repeatedly had other experiences of electronic equipment acting strangely when you are in the vicinity?

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It's not just the conductivity that blocks GPS signals. A very thin film of solid water will block the signals, even relatively pure water such as rainfall. Rain itself won't block the signals, but your hand, or a wet cover or such over the antenna will block all signals. A sheet of water on the windshield will also block the signals, but we generally don't allow a continuous sheet to stay there when driving. The wipers remove it well enough.

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I just successfully magnetized some of my stainless steel knives with a permanent magnet. So it is indeed possible the rod inside you can be affecting your flux gate compass in your gps. Why not call your local hospital and talk to the MRI techs and see if they have any suggestions to demagnetize it? The knife that I used only put my compass off 90 degrees max. I could not get it to point to it rather than mag north.

 

HummerH1

post deleted.

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Compasses in ship, 'aeroplanes', cars, and everything else have to be compensated. The reason they call them magnetic compasses is because the needle is a magnet, and will be attracted to any ferrous metal nearby. Being in the middle of a ship, the effect tends to be nullified somewhat by having steel all around, but they still have to be compensated. Hold your magnetic compass still, or lying on something, and bring a piece of iron close to it. The needle will move, as the magnet is attracted to the iron. The effect is of course greater if the iron is magnetized, since magnets attract each other (or repel each other, depending on the orientation).

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Holy smokes, you've all taken this to a whole new level. :D That's what I get for asking a question on a board full of geeks. LOL B) BTW, that was "geeks" in the nicest sense.

 

DH has guards Sunday, but weather permitting Monday, we'll try to do some of your tests. Thanks for all the help.

 

But its like talking to my dad, the electrical / mechanical engineer. I didn't understand 1/2 of it. lol j/k

Edited by wandering4cache
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Vinny & Sue Team: Wow!

 

Now THAT is a reply of note!

 

Very interesting (as this whole thread has been) so many thanks for the time to reply to my post in particular.

 

I look forward to seeing more about this whole topic, as I am learning a great deal - even at my advanced age!

 

For instance - I didn't know about the water affecting the gps. If my little Explorist is soaking wet in the rain will my reception be adversely affected?

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Vinny & Sue Team: Wow!

 

Now THAT is a reply of note!

 

Very interesting (as this whole thread has been) so many thanks for the time to reply to my post in particular.

 

I look forward to seeing more about this whole topic, as I am learning a great deal - even at my advanced age!

 

For instance - I didn't know about the water affecting the gps. If my little Explorist is soaking wet in the rain will my reception be adversely affected?

Thanks for your kind words. Regarding your question about water: a thin layer or film of water will have little attenuation to RF signals in the range used by the GPS satellites, and so if your Explorist is wet, there should not be any significant attenuation of signals. On the other hand, if you are standing in a dense forest, and all of the branches and leaves of all the trees are soaking wet from the same rainfall, you can usually expect to see the signals from the GPS satellites attenuated by anywhere from 3 decibels (3 dB, or a reduction to half strength) to 6 dB (a 4X change in signal strength) or more compared to standing in the same forest on a dry day, particularly for satellites which are located within about 30 degrees of the visual horizon. For satellites which are located more directly overhead, the attenuation will likely be somewhat less.

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