%YAML 1.1
---
$schema: "http://stsci.edu/schemas/yaml-schema/draft-01"
id: "http://stsci.edu/schemas/asdf/transform/conic_equidistant-1.1.0"
title: |
  Conic equidistant projection.

description: |
  Corresponds to the `COD` projection in the FITS WCS standard.

  See
  [conic](ref:schemas/conic-1.1.0)
  for the definition of the full transformation.

  The transformation is defined as:

  $$C &= \frac{180^\circ}{\pi} \frac{\sin\theta_a\sin\eta}{\eta} \\
    R_\theta &= \theta_a - \theta + \eta\cot\eta\cot\theta_a \\
    Y_0 = \eta\cot\eta\cot\theta_a$$

  Invertibility: All ASDF tools are required to provide the inverse of
  this transform.

allOf:
  - $ref: "conic-1.1.0"
...
