Dusty, I believe Futenma had its own compass calibration area, right? I was involved in getting one set up there as a joint Marine/USAF effort in 1971, or somewhere around that time. It involved doing a survey of the area to avoid magnetic anomalies created by buried steel leftovers from the WW II invasion. My grandfather's younger brother died on the beach there in 1945 when he caught a piece of shrapnel in the forehead.
Clark AFB did not have any area magnetically stable enough to do a compass swing, due to buried debris under the ramp.
Jerry
