h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

If you draw a great circle through any two points on the Earth's surface, you have a choice of two routes between the points, both of which lie along the circle. One will be short, the other, generally, not.

Well, mathematically you are correct - except in the case where they are equal, one is the minimum distance and the other is the maximum. In navigation, only one of the routes is of interest, so I had not troubled about the other. A change to the first sentence may be in order - I will give it some thought. Thanks

I find this useful for planning routes to eclipse tracks & c.

http://williams.best.vwh.net/gccalc.htm

Excellent link Thanks! I've been using excel, but it's a little clunky for this kind of thing. Ok, more than a little.

I'm forced into using that product too, sometimes. Here's one about the electricity consumption hereabouts...


http://newolder.netfirms.com/Screw%20Loose%20electricity.htm