I understand that the suggestion I gave was simplistic... that was the point. Once Jim figures out the compass rose then add the next layer. You can't just throw a bunch of jargon out and expect Jim's light bulb to come on.
Now that magnetic variation is understood, we can add deviation.
What is deviation, how do we measure deviation, why is deviation important.
I've seen many posts on Sailnet where someone has a simple question and they get the most drawn out, lengthy, over the top answers you can imagine. Jim had a question about magnetic variation, so you all throw out the whole TVMDC..... just answer the V question and then build on it with the rest....it can be confusing if you are new to it.