Simple- - - - -I was stationed at "Clark Field" in the Phillipines, which was built over enough WW II scrap iron that the the whole ramp had so many magnetic anomalies we couldn't calibrate a compass anywhere on the base. We had to send the planes to some other maintenance facility where the earth's magnetism was closer to normal. Hence the "magnetic field" reference!
LOL!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!