Lambert Chart
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Lambert Chart
Hey!
Can someone explain me or give me some hints how to pick out course and distances in a lambert chart?i have difficulties because the meridians are curved etc.
does somebody know a good webpage?
Thanks!
OD
Can someone explain me or give me some hints how to pick out course and distances in a lambert chart?i have difficulties because the meridians are curved etc.
does somebody know a good webpage?
Thanks!
OD
Join Date: Jan 2004
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A Lamberts chart has the following properties:
Convergency is constant across the chart and is equal to earth convergency at the parallel of origin.
To find the constant of the cone, either sin PO, or divide the angle of the projection by the coverage (can’t think of a better way to explain this without a diagram)
Scale is correct at the standard parallels.
Scale is expanded by 1% moving away form the standard parallels, and contracted by 1% moving towards the PO
Great circles are curved lines, concave to the PO
Rumb lines are curved lines concaved to the nearer pole
Now having said that. The degree of curvature in a great circle is so small that we can use the lamberts for plotting radio bearings as great circles. Convergency is not required like a mecator
When measuring the length of a track, the easiest way is to use a set compasses (what is plural for that?) and place between the two points. Then offer that to the nearest meridian of longitude. Meridians by the way are straight lines on a lamberts. They are converging towards the nearer pole, but they will not meet except on a polar stereo graphic chart.
When measuring the course that you’ve plotted, measuring at either end will give the initial and final great circle track, measuring half way along the course will give the rumb line track
If you still don’t understand the chart (difficult to explain in one post or without diagrams) I found that the Underdown book of Navigation is good. It does go into too much depth in some things, but overall it’s ok
IBR
Convergency is constant across the chart and is equal to earth convergency at the parallel of origin.
To find the constant of the cone, either sin PO, or divide the angle of the projection by the coverage (can’t think of a better way to explain this without a diagram)
Scale is correct at the standard parallels.
Scale is expanded by 1% moving away form the standard parallels, and contracted by 1% moving towards the PO
Great circles are curved lines, concave to the PO
Rumb lines are curved lines concaved to the nearer pole
Now having said that. The degree of curvature in a great circle is so small that we can use the lamberts for plotting radio bearings as great circles. Convergency is not required like a mecator
When measuring the length of a track, the easiest way is to use a set compasses (what is plural for that?) and place between the two points. Then offer that to the nearest meridian of longitude. Meridians by the way are straight lines on a lamberts. They are converging towards the nearer pole, but they will not meet except on a polar stereo graphic chart.
When measuring the course that you’ve plotted, measuring at either end will give the initial and final great circle track, measuring half way along the course will give the rumb line track
If you still don’t understand the chart (difficult to explain in one post or without diagrams) I found that the Underdown book of Navigation is good. It does go into too much depth in some things, but overall it’s ok
IBR
