Age of magnetic variation data on CAA charts
 

I'm currently writing a batch routine to update magnetic variation data based on future dates and differing models with the raw data being lat/long co-ordinates.

My initial findings are somewhat scary, the magnetic variation data on my 2004 chart is probably about 10 years old.

Can anybody confirm it's exact age?

Many thanks.

I can't help you directly but, if the UK CAA complies with ICAO Annex 4 then the magnetic declination shouldn't be more than 5 years old. The 5-year cycle is based on years that are divisible by 5, so, e.g. ... 1980, 1985, 1990, 1995, 2000, 2005, etc. There's a caveat or two on the 5-yr cycle, but that is the basis of the whole thing.

Which particular 2004 chart would this be? My 2004 CAA S England 1:500,000 has variation lines for July 2004, with an estimated decrease of 7 minutes per year. All stated in the legend in the bottom left.

...and if you are looking at enroute charts & magentic tracks, they are based on station declinations that may be different from the local magnetic variation....