Class: Astronoby::Topocentric

Inherits:
ReferenceFrame show all
Defined in:
lib/astronoby/reference_frames/topocentric.rb

Overview

Topocentric reference frame. Represents a body’s position as seen from a specific observer on Earth’s surface, accounting for the observer’s geocentric position and Earth rotation.

Instance Attribute Summary

Attributes inherited from ReferenceFrame

#center, #instant, #position, #target_body, #velocity

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from ReferenceFrame

#distance, #equatorial, #separation_from

Constructor Details

#initialize(position:, velocity:, instant:, center:, target_body:, observer:) ⇒ Topocentric

Returns a new instance of Topocentric.

Parameters:



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# File 'lib/astronoby/reference_frames/topocentric.rb', line 49

def initialize(
  position:,
  velocity:,
  instant:,
  center:,
  target_body:,
  observer:
)
  super(
    position: position,
    velocity: velocity,
    instant: instant,
    center: center,
    target_body: target_body
  )
  @observer = observer
end

Class Method Details

.build_from_apparent(apparent:, observer:, instant:, target_body:) ⇒ Astronoby::Topocentric

Builds a topocentric frame from an apparent frame and observer.

Parameters:

Returns:



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# File 'lib/astronoby/reference_frames/topocentric.rb', line 15

def self.build_from_apparent(
  apparent:,
  observer:,
  instant:,
  target_body:
)
  matrix = observer.earth_fixed_rotation_matrix_for(instant)

  observer_position = Distance.vector_from_meters(
    matrix * observer.geocentric_position.map(&:m)
  )
  observer_velocity = Velocity.vector_from_mps(
    matrix * observer.geocentric_velocity.map(&:mps)
  )

  position = apparent.position - observer_position
  velocity = apparent.velocity - observer_velocity

  new(
    position: position,
    velocity: velocity,
    instant: instant,
    center: Center.topocentric(observer),
    target_body: target_body,
    observer: observer
  )
end

Instance Method Details

#ecliptic ⇒ Astronoby::Coordinates::Ecliptic

Returns ecliptic coordinates at the current instant (true ecliptic and equinox of date).

Returns:



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# File 'lib/astronoby/reference_frames/topocentric.rb', line 69

def ecliptic
  @ecliptic ||= begin
    return Coordinates::Ecliptic.zero if distance.zero?

    equatorial.to_ecliptic(
      instant: @instant,
      obliquity: TrueObliquity.at(@instant)
    )
  end
end

#horizontal(refraction: false) ⇒ Astronoby::Coordinates::Horizontal

Converts to horizontal coordinates (azimuth/altitude).

Parameters:

  • refraction (Boolean) (defaults to: false) —

    whether to apply atmospheric refraction correction (default: false)

Returns:



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# File 'lib/astronoby/reference_frames/topocentric.rb', line 85

def horizontal(refraction: false)
  horizontal = equatorial.to_horizontal(
    time: @instant.to_time,
    observer: @observer
  )

  if refraction
    Refraction.correct_horizontal_coordinates(coordinates: horizontal)
  else
    horizontal
  end
end