Great circle course

[brokesailor]

If you plot a course between two distant points on a GPS using vector charts is this the great circle route (shortest route)?

[Zanshin]

No, it is not a great circle route. Usually the GPS plotted course will have one compass course for the whole trip, whereas a great circle route has changes in compass course. If your course is N-S or less than a thousand miles, the distance differences are going to be less than those imposed by making one or two bad tacks.

[celenoglu]

I tried it with max sea with vector maps and the route is great circle.

[PBzeer]

It's going to depend on how your particular navigation program is set up.

[Zanshin]

I just checked Garmin's website and they state that

GPS normally uses great circle calculations for distance and desired track.

On an east-west crossing 90 degrees of longitude (1/4 of the earth's circumference) at around 20 degrees N, the difference between rhumb line and great circle is 124Km on a distance of 8166km. The difference at the equator is 0 but at higher latitudes it makes more of a difference.