General Navigation question 1
Thread Starter
Join Date: Apr 2003
Location: england
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
General Navigation question 1
a lambert conformal conic chart has a constant of the cone 0.80.
A straight line course drawn on this chart from A (53N 004W) to B is 080 at A, course at B is 092 T.
What is longitude of B?
explaination please
A straight line course drawn on this chart from A (53N 004W) to B is 080 at A, course at B is 092 T.
What is longitude of B?
explaination please
Join Date: Nov 2001
Location: London
Posts: 60
Likes: 0
Received 0 Likes
on
0 Posts
The formula for Chart Convergency (CC) on a Lambert conformal conic chart is:
CC = dlong x sin P of O
Constant of the Cone is sin P of O calculated for you
Straight lines on Lamberts approximate to Great Circles (GC), so you are looking at a GC. If Initial GC is 080 and Final GC is 092 the convergency is the difference between the two = 12 degrees
Going back to your formula for CC
CC = dlong x sin P of O
12 = dlong x 0.8
dlong = 15 degrees
From 004W you end up at 011E
CC = dlong x sin P of O
Constant of the Cone is sin P of O calculated for you
Straight lines on Lamberts approximate to Great Circles (GC), so you are looking at a GC. If Initial GC is 080 and Final GC is 092 the convergency is the difference between the two = 12 degrees
Going back to your formula for CC
CC = dlong x sin P of O
12 = dlong x 0.8
dlong = 15 degrees
From 004W you end up at 011E
Jet Blast Rat
Join Date: Jan 2001
Location: Sarfend-on-Sea
Age: 51
Posts: 2,081
Likes: 0
Received 0 Likes
on
0 Posts
Aim High's answer is correct, theory is almost right. Sorry to be a pedant!
Chart convergence represents the change in bearing of a straight line drawn on that chart. Earth convergence gives change of great-circle bearing. The question gives the straight line bearings, from which we can work out the change, 12°. This is itself, therefore, chart convergence. The proximity of the straight line to a great circle is not required.
The formula AH used was for chart convergence, so the exact change of longitude is 15° as correctly calculated.
Chart convergence represents the change in bearing of a straight line drawn on that chart. Earth convergence gives change of great-circle bearing. The question gives the straight line bearings, from which we can work out the change, 12°. This is itself, therefore, chart convergence. The proximity of the straight line to a great circle is not required.
The formula AH used was for chart convergence, so the exact change of longitude is 15° as correctly calculated.
