Not necessarilly. Great Lake charts are in statute miles and use Poly
Conic projection, rather than the Mercator that the off shore charts
use.
Reply
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An exception somewhat proving the rule.
I'm not familiar with charts for the Great Lakes, of course, but it's
surprising they wouldn't follow the convention of the majority of the
world.
Do Great Lakes sailors discuss vessel speed or wind speeds in knots or
MPH?
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I'm told that the Lakes use statute miles because of the land mass
involved in the charts. However, had the St. Lawrence Seaway came into
being sooner, bringing "salties" to the Lakes, the chartmakers might
have decided to use the "off-shore" type of chart and nautical miles to
avoid confusion. As far as speed terminology, you hear both.