"Dale DePriest" wrote in message


You mean your magnetic heading. You have your actual heading. You need
a table of magnetic variations and interprolate from the table based on
your location as there is no mathmatical model that will provide this
information reliably.


I found the post a little confusing because it seemed to be mixing
the problem of the course heading changing due to the great circle
route (mentioned in the subject) with heading changes due to changing
declination mentioned in the body. Two very different issues.

Steve