ATPL NAV Q?- Great Circles & Rhumb Lines

[frogone]

Hi guys,

I'm currently studying for the JAA ATPL exams through a distance learning course. Anyone got any advice on Great Circles and Rhumb lines?? The penny is droping, but, slowly! Links and advice is apprciated

Cheers,

KOMN :(

[Teroc]

Can you be more specific as to what info you need Komn?
As for definitions Great circles are circles whose diameter and centre is that of the earth itslf. I.E. The equator and any line of longitude. If you cut the earth perfectly in half each circumference would be a great circle. Apart from the equator no line of latitude is a great circle.
Rhumb lines are straight lines which cross lines of lontitude at the same angle. Great circle lines cross each successive lines of long. at different angles and is the shortest distance between 2 points on earth

If you bang it into any search engine you'll get links to sites which explain it better than me.

Thats what I rememeber anyway. Shoot me down folks as my memory aint what it used to be :)

[tunneler]

Easy peasy..........

Firstly, go out and buy a green pen and a red pen.

Use the Green pen for a great circle.
Use the Red pen for a rhumb line.

Now all you have to remember that the great circle will always be shorter than the rhumb line and hence will always be closer to the pole......

Northern Hemisphere - Rhumb Line = Smiley Face & Great Cricle = Sad face

Southern Hemisp`here - Swop em around :)

All the best.

Tunny :)

[Rob 747]

Thank God someone asked this question. Its been doing my head in for ages now.

Thats a damn fine explanation Teroc http://www.stopstart.fsnet.co.uk/smilie/cheers.gif

Now how about conversion angles? http://www.stopstart.fsnet.co.uk/smilie/huh.gif

[jar man]

a good way of thinking about 'rhumb lines' vs 'great circles' is to think of the earth as an orange. If you slice the orange through the middle and get 2 equal halves then you sliced a great circle. If you don't slice through the middle and get one big bit and one smaller bit then you sliced a rhumb line....it doesn't matter what angle...or where on the orange you slice...the principle is the same.

[Capt Wannabe]

Tunny, sorry to be really pedantic, but a GC will not always be shorter than a Rhumb Line. It could be the same length, but never longer :D

[Chirpy Pilot]

Never understood all that stuff.
Just answer C
It worked for me

[tunneler]

Smartarse! :D :D :D

[Rote 8]

Rhumb line always on the equatorial side of the Great Circle. I remember this by thinking about rum - it always comes from hot, equatorial countries.