NavList:

Magnus Sjoquist you wrote:  but: with my handheld GPS (Garmin GPS 12)            5152 NM!

I suspect that the handheld GPS did convert the GC-minutes into NM, but I am not very good at contruction of satellite navigators. If anyone on the NavList feels like explaining this discrepancy I would be truly grateful.

Good old Garmin GPS12.  I’m glad to see I’m not the only user.  Garmin don’t support them anymore, which is a pity.  Like Robin, I was going to suggest you tried a setting a few different datums to see which values came up.  I’d try it myself but I’m not sure how to make a GPS 12 stop at a false start point and not search for its true position.  Perhaps you can use the route function.  Also, how does it cope with height, if at all?  Is there an inside and outside of the running track possibility.  We know that indicating height is the least accurate GPS function.

Bearing in mind the distances involved, I don’t think 12nm difference is too bad.  I see that in Nov 2000, I calculated the great circle distance from 51°30’N 000°05’W (London) to 40°43’N 73°59’W (New York) as 5,578km using a hand-held calculator and the geodesic distance as 5,587km.  Don’t ask me to remember how to do it today.  That’s about 0.17% difference between the two.  Compared to your example, it’s about half the difference over about half the distance.  DaveP