[CQ-Contest] ITU Zone Definition Question

[Michael Adams]

So, I'm visiting my childhood home this week, and I'm hoping to get in a little time to play radio.

When doing a bit of log configuration in anticipation of this, I encountered a question I don't know the answer to:

Is there any kind of formal definition for how ITU zone is defined for stations that are located on a zone boundary?  Or, does it boil down to "just pick one"?

(At the moment, my car is parked at exactly 90 degrees west according to the GPS.   According to USGS topo maps, my butt is on the 90th meridian as I type this.)

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Michael Adams | N1EN/4 | mda at n1en.org