Historic variation
 

Here's an odd one. Anyone know where I can find records of magnetic variation at historic points in the past?

Specifically the need is to reinterpret maps drawn on the Western Front in the first world war, which were orientated in relation to magnetic North. But where was that in 1916-18 if you were in France?

Much appreciate the answer if anyone knows.

I googled "historic magnetic variation ?" and it gave me 1,400,000 results in 0.13 secs. From the quality of the first few sites, there should be enough to answer your query, using your specifics. Probably depends what accuracy you need and whether a degree of interpolation is acceptable. Good luck. LFH