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Off topic as it mentions GPS, but...

I recalled reading that my Garmin gave me great-circle distances between two
waypoints as standard.  I thought, what good is that when it gives me a
rhumb line course?  In fact, it gives a constantly updated great-circle
route.

Tried using simulation mode from home waypoint (Lafayette, IN) to a waypoint
40d 27' N and 93 W (same latitude, but opposite side off the globe).  Course
given was not 90d or 270d, but straight north over the pole.  Mercator
charts would have one steering due east or west for 8071 sm, as opposed to
5945 sm along the great-circle route.

(Yes, statute miles.  Had just used the GPS for bushwhacking, and had not
switched back to nautical miles--hard water now.  Despite the fact Great
Lakes charts are in statute miles, my friends do use nautical miles on the
water.  Just easier for most navigation.)

Then entered a waypoint just west of England at my latitude (due west of
Lafayette--over 4285 sm on the great circle) set to top speed of 1150 mph,
and turned the unit loose.  It started off with a course of 59d, then to 60d
and so on until the halfway mark (over 2142.5 sm) where is hit 90d.  Finally
approach to the waypoint was a course of 121d, which is what I had
anticipated given the starting course difference from 90d

Interesting to check in on its progress, and certainly not documented in my
76 instruction pamphlet.

Bill

   

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