I'm making a declination chart (True North -> Grid North -> Magnetic North) for a map I plan on using, and I need some sanity check from the community:

The convergence from True to Grid north is 1° (positive east) the declination from True North to Magnetic North is 5° (positive east). If I want to physically orient the map to GN for my plotting, is my GM angle 4 or 6°?

I'm almost sure it is 4°, but some sanity check wouldn't hurt.

1 Answer 1


So I guess I'll answer my own question then... GM (or GMA) angle indicates only the declination or angular difference between Grid and Magnetic North. So in my case, it's 4°. If Grid north was west of True & Magnetic North, I would have to add the difference between Grid, True North, and Magnetic North. If Grid North is east of both True North & Magnetic North I'll have to subtract again the difference between Grid & True North.

Edit: Too bad I can't upvote my own question & answer since they were both useful for me.

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