Definition

1. Noun:
   • A map projection in which the Earth's surface is projected onto a series of cones, each tangent to a different parallel of latitude. This method aims to preserve accurate distances along each parallel and along the central meridian, resulting in minimal distortion along a narrow north-south region.

Usage

• The polyconic projection is often used for mapping large countries with a significant north-south extent, such as the United States.
• In this polyconic projection, meridians are curved lines rather than straight, which distinguishes it from simpler conic projections.
• For topographic mapping series, the polyconic projection was historically a standard choice due to its balance of properties over a limited area.

Advanced Usage

• "To be constructed on a polyconic projection": This phrase describes a map whose mathematical basis is the polyconic method.
  • The historical survey maps were constructed on a polyconic projection.
• "Polyconic projection properties": Refers to the specific characteristics of this projection type, such as its conformality, scale, and distortion patterns.
  • The cartographer explained the polyconic projection properties, noting it is neither fully conformal nor equal-area.

Variants and Related Words

• Conic Projection (n): A broader class of map projections that use a cone as the developable surface. The polyconic projection is a specific type within this class.
• Map Projection (n): The general term for any systematic method of representing the surface of a sphere or ellipsoid (like the Earth) onto a flat plane.

Synonyms

• American Polyconic Projection: A specific, common name for this projection.
• Ordinary Polyconic Projection: Another technical name used to distinguish it from modified versions.

Related Terms (Conceptual)

• Central Meridian: The line of longitude at the center of a map projection, often where distortion is minimized. In a polyconic projection, scale is true along this line.
• Standard Parallel: A line of latitude where the developable surface (cone) touches the globe, and scale is true. A polyconic projection uses multiple standard parallels.
• Developable Surface: The geometric shape (cone, cylinder, plane) onto which the globe is projected for the purpose of creating a flat map.

Noun

1. a conic projection of a map having distances between meridians equal to those distances on a globe