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 23rd Jun 2012, 07:14 #1 (permalink) Join Date: Nov 2009 Location: PK Posts: 125 Lat Long Calculations Hi An aircraft departs a point 0400N 17000W and flies 600 nm South, followed by 600 nm East, then 600 nm North, then 600 nm West. What is its final position? a) 0400N 17000W b) 0600S 17000W c) 0400N 16958.1W d) 0400N 17001.8W c) marked correct, however I am ending up at (d). Can anyone please check the calculations: Starting at 0400N 17000W Flying 600nm South (600/60 = 10 deg) the position becomes 0600S 17000W Flying 600nm East (600/cos6 = 10.055 deg. 170+10.055 = 180.055. 360-180.05= 179.9449) the position becomes 0600S 179.9449E Flying 600nm North (600/60 = 10 deg) the position becomes 0400N 179.9449E Flying 600nm West (600/cos4 = 10.024 deg. 179.9449+10.024 = 189.9689. 360-180.9689= 170.03) the position becomes 04°00'N 170°1.8'W Regards
23rd Jun 2012, 07:29   #2 (permalink)

Join Date: Feb 2001
Location: Planet Earth (sometimes)
Posts: 2,039
Just by looking at this over breakfast, no calculator to hand so I can't check the sums but IMHO I reckon C is most probably correct. Your 600 n.m. of eastbound flight at 6 degrees south covers more degrees of longitude than the opposite direction 600 n.m westbound at 4 north ( because the earth is "thinner" at 6 south than at 4 north , i.e; the lines of longitude are closer together ) , therefore having flown your 600 n.m box you must end up east of where you started....

After after closer inspection and another coffee I think it might be worth taking a look at your leg two calculation:

I agree the leg starts at 0600S 17000W, - the question states you fly east for 600 nm.

You've written:

Quote:
 Flying 600nm East (600/cos6 = 10.055 deg. 170+10.055 = 180.055. 360-180.05= 179.9449) the position becomes 0600S 179.9449 E
I've emphasised a few points ...., this might be a classic case of a quick picture or rough diagram being worth a thousand calculations.

Last edited by wiggy; 23rd Jun 2012 at 08:28.

23rd Jun 2012, 09:34   #3 (permalink)

Join Date: Nov 2009
Location: PK
Posts: 125
Quote:
 picture or rough diagram being worth a thousand calculations
Provided it is correct. I went west instead of east

Thanks Wiggy

 23rd Jun 2012, 09:51 #4 (permalink) Join Date: Feb 2001 Location: Planet Earth (sometimes) Posts: 2,039 You're welcome, good luck with the exams.

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