With Equidistant Conic (Simple Conic) projections, correct distance is achieved along the line(s) of contact with the cone, and parallels are equidistantly spaced. It can be used with either one (A) or two (B) standard parallels.

Construction | Cone |

Property | Equidistant |

Meridians | Meridians are straight lines converging on a polar axis but not at the pole. |

Parallels | Parallels are arcs of concentric circles concave toward a pole. |

Graticule spacing | Meridian spacing is true on the standard parallels and decreases toward the pole. Parallels are placed at true scale along the meridians. Meridians and parallels intersect each other at right angles. The graticule is symmetrical. |

Linear scale | Linear scale is true along all meridians and along the standard parallel or parallels. |

Uses | In atlases for portraying mid-latitude areas. Regions with a few degrees of latitude lying on one side of the Equator. Used in former Soviet Union for mapping the entire country (Environmental Systems Research Institute, 1992). |

This projection is neither conformal nor equal-area, but the north-south scale along meridians is correct. The North or South Pole is represented by an arc. Because scale distortion increases with increasing distance from the line or lines of contact, the Equidistant Conic is used mostly for mapping regions predominantly east-west in extent. The USGS uses the Equidistant Conic in an approximate form for a map of Alaska.

This projection contains these unique parameters:

One or two standard parallels?

Latitude of standard parallel

Enter one or two values for the desired control line or lines of the projection, that is, the standard parallel. Note that if two standard parallels are used, the first is the southernmost.

Equidistant Conic Projection

Source: Snyder and Voxland, 1989