Lambert Conformal Conic

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A conformal conic projection. Also known as the Conic Orthomorphic projection. A USGS and Manifold favorite for maps of the US. The Lambert Conformal Conic (Single Parallel) choice is a simplified version that uses only one parallel.

 

Scale

 

True along one or two chosen standard parallels, usually but not necessarily on the same side of the Equator. As a rule of thumb, these parallels can be placed at one-sixth and five-sixths of the range of latitudes, but there are more refined means of selection.

 

Scale is constant along any given parallel and is the same in all directions at a given point.

 

Distortion

 

Free of distortion only along the one or two standard parallels. Distortion is constant along any given parallel. Conformal everywhere except at the poles.

 

Usage

 

Extensively used in ellipsoidal form for large-scale mapping of regions of predominantly east-west extent, including topographic quadrangles (1:24,000 and 1:62,500 scale) for many of the U.S. State Plane Coordinate system zones, many maps in the International Map of the World (1:1,000,000 scale) series, the U.S. State Base Maps (1:500,000 scale), and topographic mapping in many other nations.

 

Also used for atlas maps of some countries. Recommended for conformal mapping of regions of predominantly east-west extent, such as the US or Russia.

 

Limitations

 

Normally used only for a single hemisphere.

 

Origin

 

Presented by Johann Heinrich Lambert (1728-1777) of Alsace in 1772.

 

Limiting Forms

 

Polar Stereographic projection: if a pole is made the single standard parallel. The cone of projection thereby becomes a plane.

 

Mercator projection: if the Equator is the single standard parallel or if two standard parallels are symmetrically placed north and south of the Equator. The cone of projection thereby becomes a cylinder.

 

Options

 

Specify the first standard parallel and second standard parallel to tailor the projection to the area to be mapped.

 

Specify the latitude origin and longitude origin to center the map projection to the area to be mapped. Specifying a non-Equatorial or non-polar origin causes an oblique projection.

 

The Lambert Conformal Conic (Single Parallel) choice is a simplified version that uses only one parallel, the central latitude. This has slightly more distortion than the full version since the cone of projection is tangent to the Earth at the one parallel.

 

Example

 

For maps of the United States, reasonable figures are 38 for the Center Latitude and -100 for the Center Longitude. This is a spot approximately in the center of the lower 48 states of the United States.

 

Use 32 for the 1st Standard Latitude and 44 for the 2nd Standard Latitude when using the full Lambert Conformal Conic version.

 

These are not hard and fast numbers. One may easily use 40 for the Center Latitude and 96 for the Center Longitude, which is probably closer to what most people would consider the "center" of the US. The important thing is to pick reasonable numbers that will be consistently used throughout one's mapping, so that one's projected maps using Lambert Conformal Conic to show the US will likely be the same. We use -100 because it is an easy number to remember, and Latitude 38 because it is the easily remembered name of a cool sailing journal on the West Coast (see www.latitude38.com).