page_title: Circle of equal altitude
section_title: Parameters
hierarchical_section_title: Circle of equal altitude / Parameters
caption_attribution_description: Español: Parámetros de la circunferencia de alturas iguales
context_page_description: The circle of equal altitude also called circle of position, CoP, is the real line of position in celestial navigation. It is defined as the locus of points on the Earth on which an observer sees a star, at a given time, with the same observed altitude. It was discovered by the American sea-captain Thomas Hubbard Sumner.
context_section_description: The center of the CoP, is the substellar point or geographical position of the observed body, and its radius is the great circle distance equal to the zenith distance of the body.
  Center = geographical position of the body: (B, L) = (Dec, GHA)
  Radius = zenith distance: zd [nm] = 60 ⋅ (90 - Ho)
caption: Parameters of a circle of equal altitude
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