Gauss Meters & Magnetic Fields?

[rgranger]

Hey All

I need to measure the magnetic field strength and direction at an outdoor research site and I figured my sailing buddies probably know as much about this as anyone.

When NOAA prints a chart that has magnetic deviations listed on them, how are those deviations measured? Are they simply charting the difference between true north and what a compass says is north or are they actually measuring magnetic fields? Seems like I could just take a GPS north vs. compass north for a deviation.

And I have heard of people hiring out to a specialist to locate the ideal position on a boat for a compass. Are they simply measuring magnetic field strengths in various locations on the boat? I found some simple Gauss Meters on line but I'm not confident that I'm in the right ball park here.

Thanks in advance,

r

 

[ifmdalvey]

I think you are mixing up variation and deviation.
The location of the compass on a boat will do nothing for variation, that is only dependent on your geographical location.
The physical location of the compass in relation to metal parts of the boat will chang readings of deviation, which will also change with heading, hence, why you should have a deviation card produce following a compass swing.

 

[Mark Maulden]

Variation is the angular difference between the geographical north pole and the magnetic north pole at a given location. That number is obviously different and dependent where on the planet you are located. The magnetic north pole is also constantly changing so the variation numbers do change every "few" yrs. Deviation is the differences induced by the compass surroundings and is a correction factor which produces the compass deviation card after the compass is swung.

Do not try to install a compass based on gauss meter readings. Magnetic field strength readings will be the same over the entire area of the boat. The differences will be pertubations of any ferrous materials all over the boat. You would go crazy mapping this all out assuming you have a "good" meter and know how to use it. Dont waste your time or money unless you just like to tinker...

 

[rgranger]

Okay guys... I can see this thread getting off topic and into the nuances of terms deviation and variation.... and everything and anything nautical.

I am NOT installing a compass (see original post). I need to measure the magnetic fields at an outdoor field site (it is for some research I'm doing). I'm asking how magnetic fields are typically measured outdoors.

 

[DayDreamer41]

You peaked my interest to go look for some information, here's what I found, kind of an interesting subject matter
https://www.nde-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/Measuring.htm