Lambert Conformal Conic

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This projection is very similar to Albers Conical Equal Area, described previously. It is mathematically based on a cone that is tangent at one parallel or, more often, that is conceptually secant on two parallels. Areal distortion is minimal, but increases away from the standard parallels. North or South Pole is represented by a point—the other pole cannot be shown. Great circle lines are approximately straight. It retains its properties at various scales, and sheets can be joined along their edges. This projection, like Albers, is most valuable in middle latitudes, especially in a country sprawling east to west like the US. The standard parallels for the US are 33° and 45°N.

Construction

Cone

Property

Conformal

Meridians

Meridians are straight lines converging at a pole.

Parallels

Parallels are arcs of concentric circles concave toward a pole and centered at a pole.

Graticule spacing

Meridian spacing is true on the standard parallels and decreases toward the pole. Parallel spacing increases away from the standard parallels and decreases between them. Meridians and parallels intersect each other at right angles. The graticule spacing retains the property of conformality. The graticule is symmetrical.

Linear scale

Linear scale is true on standard parallels. Maximum scale error is 2.5% on a map of the United States (48 states) with standard parallels at 33°N and 45°N.

Uses

Large countries in the mid-latitudes having an east-west orientation.

United States (50 states) Base Map uses standard parallels at 37°N and 65°N. Some of the National Topographic Map Series 7.5-minute and 15-minute quadrangles, and the State Base Map series are constructed on this projection. The latter series uses standard parallels of 33°N and 45°N.

Aeronautical charts for Alaska use standard parallels at 55°N and 65°N.

National Atlas of Canada uses standard parallels at 49°N and 77°N.

The major property of this projection is its conformality. At all coordinates, meridians and parallels cross at right angles. The correct angles produce correct shapes. Also, great circles are approximately straight. The conformal property of Lambert Conformal Conic, and the straightness of great circles makes it valuable for landmark flying.

Lambert Conformal Conic is the State Plane coordinate system projection for states of predominant east-west expanse. Since 1962, Lambert Conformal Conic has been used for the International Map of the World between 84°N and 80°S.

In comparison with Albers Conical Equal Area, Lambert Conformal Conic possesses true shape of small areas, whereas Albers possesses equal-area. Unlike Albers, parallels of Lambert Conformal Conic are spaced at increasing intervals the farther north or south they are from the standard parallels.

Lambert Conformal Conic Projection

map_projection_lambert_conformal_conic

In the figure above, the standard parallels are 20°N and 60°N. Note the change in spacing of the parallels.