Declination in Southern Hemisphere vs Northen Hemisphere

[darsenator]

Hi All,

Just hoping for input for a learning check/confirmation query.

Reading up about converting between Magnetic and Grid Bearings and how one must subtract or add depending on whether magnetic declination is east or west of true north.

In Victoria you subtract when converting from Map to land. The reverse applies when going from land to map (you Add)
In Western Australia you add when converting from Map to Land.The reverse applies when going from land to map (you Subtract)
<I'm aware that not all of W.A has a west-declination and that an agonic line passes through Kalgoorlie and Onslow,WA>
Obviously if one was navigating in this agonic line,then magnetic-declination is '0' so there would be no need to do any conversion.


GM = Grid TO Magnetic
MG = Magnetic TO Grid

Does the same conversion rule/formula apply when navigating in a 'Northern Hemisphere' and/or whether it's in reverse?
So if I'm in the US where there is a 20 Degree East declination, does the same formula apply or is it in reverse ?

http://geokov.com/education/magnetic-declination-inclination.aspx


My confusion stems from reading the following post and how the following gets noted
"Be careful if you go to the Northern hemisphere as you need to add the degrees there!!"

http://bushwalk.com/forum/viewtopic.php?f=5&t=9023

I hope my question makes sense.

[GPSGuided]

It's not northern vs Southern Hemisphere based. Declination varies over time and is location based. Check out a global map of magnetic declination.

http://www.ngdc.noaa.gov/geomag/declination.shtml

[icefest]

The bigger issue between NH and SH is the balancing of compass needles.

[walkerchris77]

Theres plenty of apps and websites that will use your current location and tell you the magnetic declination for where u are. And u can move your location anywhere in the world.

[GPSGuided]

I like global compasses.

[walkerchris77]

I like global compasses.

+1
I brought a suunto mc-2 great compass.

[darsenator]

Just checked out the link...so basically east(positive) declination will use the same formula when converting a magnetic to grid bearing (add the amount of declination) so long as your in an area that has east declination...
Example 'Victoria,Australia vs Chile, South America"?

[darsenator]

I like global compasses.

Yep...suunto m3 global is my field compass...

Guess I'm just making sure my learning is on check.

[darsenator]

It's not northern vs Southern Hemisphere based. Declination varies over time and is location based. Check out a global map of magnetic declination.

http://www.ngdc.noaa.gov/geomag/declination.shtml

Cheers....that's a good link

What do you think though the forum replier meant when they wrote that in northern hemisphere you add the degrees?

[GPSGuided]

What do you think though the forum replier meant when they wrote that in northern hemisphere you add the degrees?

Learn from dependable information sources eg. Wikipedia etc. When it comes to declination, the only things that are relevant are where you are on Earth and when. They change all the time (see global map). As Icefest pointed out, the relevance of Nth and Sth hemisphere is in the balance of the compass needle.
http://en.wikipedia.org/wiki/Magnetic_declination

[andrewp]

It's actally the grid magnetic angle, not the magnetic declination that you need to adjust your bearing by. The grid magnetic angle is the angle between grid north and magnetic north.

The grid lines on the map are not true north. Across Australia the grid convergance varies from ~ -1.5 - +1.5.

Andrew