And thanks to you
V1... Ooops for a very well written post.
It seems that we speak the same language. Nice diagram by the way, I've copied it already
and fits very well with my own data, and the limitations incorporated to the revised FMC programme recently finished. A good confidence check!
For those with an interest in the "WHY?" of the normal 73 degrees North limit of most FMC Magnetic Variation databases, take a look at
V1... Ooops's excellent diagram where the keyhole cuts off at that latitude. The South Magnetic Pole is at a lower latitude than the North, leading to a 60 degrees latitude "cutoff" (Usually of little interest as very little traffic passes these regions as opposed to Northern regions).
411A, I agree with you regarding the KISS principal, but some folks have to manufacture the data for the end user to be able to keep it simple.
Regards,
Old Smokey