How to find true north not magnetic north?

[gary350]

Maybe I should make it clear that I have 4 compasses. 3 are low cost boy scout compasses. All 3 boy scout compasses appear to be identical and made by the same company except that 1 is green color the other 2 are black. I paid $2, $3 & $5 for the boy scout compasses so I am calling these cheap or low cost compasses. Needle sticks on the $2 green compass. The dial sticks on the $3 black compass. The $5 compass works best of the 3. I also have a more expensive compass that cost $20 but maybe the price should not be considered as making it be a better compass than the $5 compass. The $20 needle moves very smooth and the dial rotates very nice much better than the $5 compass. The more expensive compass has a stronger magnet field on the needle that is why it is more sensitive to metal objects near by. The $20 compass is hard to use to adjust my TV antenna because I have to stand too far away from the TV antenna to make adjustments. There you have it the details of my 4 compasses. I consider the $2 & $3 compass to be basically worthless. If I am lost in the wilderness I would like to have the $20 compass as long as I am not lost near a large iron ore deposit in the earth.

 

[Baluncore]

I consider the $2 & $3 compass to be basically worthless.

Do not rely on any magnetic compass, at any price. There is too much variation, local field or magnetic storm.

You read your Lat/Long with GPS earlier. Now go to a point as far away that you can see from the first site. Read the GPS there. Go back and check the first point. You now have two points on the WGS84 ellipsoid. Use navigation software to find the bearing from the first point to the second, remote point. Offset that bearing from that survey line to find the N-S meridian.

 

[Baluncore]

You can point the hour hand of a watch at the Sun, then split the angle between the hour hand and 12 o'clock, and that is True South.

But since I'm South of the equator, it gives me North.
That will only give an approximation of the North-South meridian line. It depends on your longitude in the time zone and a seasonal correction using the Analemma.
That sundial correction oscillates between –14min 15sec and +16min 25sec.
See; https://en.wikipedia.org/wiki/Analemma
https://en.wikipedia.org/wiki/Equation_of_time

 

[Dale]

The more expensive compass has a stronger magnet field on the needle that is why it is more sensitive to metal objects near by.

I doubt this is correct. I suspect that most of the difference in sensitivity is due to the better bearings

 

[anorlunda]

@gary350 , please answer the question. What are you trying to accomplish?

 

[gary350]

I doubt this is correct. I suspect that most of the difference in sensitivity is due to the better bearings

That is true the $20 does have a better needle movement. If I go out into the center of the front yard where there is no fence and no metal with 2 compasses the needle point at each other. If I put both compasses on the ground and move them apart soon Earth magnetic field becomes stronger than the other compass needle and they both stop pointing at each other and point at magnetic north.

 

[Baluncore]

If I put both compasses on the ground and move them apart soon Earth magnetic field becomes stronger than the other compass needle and they both stop pointing at each other and point at magnetic north.

When close, they should align, but with the North pole of one pointing to the South pole of the other.
When far apart, they do not both point to magnetic North, they will always influence each other.

There is no point buying a magnetic compass if you want to know true North.

QUESTION; Why do you need to know true North?

 

[anorlunda]

I think this thread has run its course.

Thread closed.