Conic Projection
Conic projection is a method of projecting maps of the Earth onto a conical surface, which is then unrolled into a flat plane. It is particularly useful for mapping regions with larger east-west than north-south extent, such as the contiguous United States, because it minimizes distortion along the lines where the cone intersects the globe.
In Depth Explanation of Conic Projection
The term 'conic projection' originates from the method's use of a cone placed over a globe, intersecting it at one or two standard parallels. These are lines of latitude where the cone touches the globe, used to maintain accuracy in the projection. The concept goes back to ancient Greek cartography, with Hipparchus being credited as one of the earliest to use this method. Conic projections are still used today for regional maps because they provide a balance between shape and area accuracy.
There are several variants of conic projection, including the Albers Equal-Area and the Lambert Conformal Conic. Each has unique properties tailored to specific mapping needs. The Albers projection preserves area but distorts shape, making it useful for thematic maps, whereas the Lambert projection preserves shape but distorts area, making it ideal for aeronautical charts and weather maps. Over time, with advancements in technology, other projections have been developed, but conic projections remain relevant due to their simplicity and effectiveness for specific applications.
A Practical Example of the Conic Projection
A practical example of conic projection is its extensive use in the creation of the United States Geological Survey (USGS) maps. The Lambert Conformal Conic projection, in particular, is frequently used for this purpose due to its ability to maintain conformality. This projection provides accurate representations of small shapes and angles, which is indispensable for tasks like aeronautical charting and weather mapping. The use of conic projection in these maps has significantly influenced navigation and planning in both civil and military aviation.