@Keith
But i really don't get the idea as to how you can draw a great circle between any two points.Consider two places placed @ the same lattitude(eg.15 degrees N) but different longitudes(say 18 degree east and 20 degree east).. Now these two places are joined by the same parallel of lattitude(which is a small circle). So how can a great circle be drawn through these 2 points?A small circle joins these 2 places.And hence the shortest distance b/w these 2 should be the small circle!
Don't worry, lots of people have problems visualising this type of thing. But it is quite easy to demonstrate it to yourself.
Take an apple or some similar sperical(ish) fruit. The moreaccuarte will be the results.
Draw your line of latitude on it and draw two dots on that line to represent your two positions.
Place the apple on a table and roll it across the surface until one of the dots is at the top of the apple. Place a knife on that dot and while keeping the knife on the top dot, move the knife until it is also directly above the other dot. Now cut straight down through the apple to the table.
You will find that you have cut through both dots and also through the centre of the apple. The edges of the cut surfaces are the great circle on which the two dots lie.