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Refer to figure.
Which of the diagrams most accurately represents the great circle route from A to B on a Lambert conformal conic chart?
  • A
    Diagram 3
  • B
    Diagram 4
  • C
    Diagram 2
  • D
    Diagram 1



Correct on the standard parallels. Contracted within the standard parallels. (least then 1% at parallel of origin).
Expanded outside standard parallels.


Yes. All charts used for navigation must be.


Meridians are straight lines, originating from the pole. Parallels are arcs of circles, centred at the pole.
(The pole is always off the map).

Parallel of Origin

Mathematical basis of projection. Assumed to be halfway between the 2 standard parallels.

Chart Convergence

Constant across the chart = Earth Convergence.

Chart convergence = ch.long × sin parallel of origin

Rhumb Lines

Meridians are straight lines. All other Rhumb Lines are concave to the pole (i.e. parallels of latitude).

Great Circles

Meridians are straight lines.
At the parallel of origin - near-straight line.
At any other latitude, a curve concave to the parallel of origin.

Therefore we are looking for a curve concave to the parallel of origin. This means that for latitudes greater than the parallel of origin curve should bulge towards pole. Diagram 2 has convex curve to the parallel of origin, Diagram 3 has partly convex curve to the parallel of origin and Diagram 4 has a straight line. Diagram 1 is the one we are looking for.

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