Module: WrfLibrary::SunEquation

Defined in:
lib/wrf_library/sun_equation.rb

Overview

module to calculate the time of the sunrise and sunset for a given location with geo coordinates and the given day as a date source: babel.hathitrust.org/cgi/pt?id=uc1.31822006852784&view=1up&seq=26

Constant Summary collapse

@@rotation_time =

Returns the rotation distance per hour.

Returns:

  • (Float) —

    the rotation distance per hour

360.0 / 24.0
@@cos_z =

Returns the zenith distance at rise and set.

Returns:

  • (Float) —

    the zenith distance at rise and set

-0.01454

Class Method Summary collapse

Class Method Details

.calculate_center_equation(date = Time.now, longitude, event) ⇒ Float

method to calculate the center equation

Parameters:

  • date (Time) (defaults to: Time.now) —

    the provided date or the current date if none is given

  • longitude (Float) —

    the longitude of the requested location

  • event (Symbol) —

    the information if sunrise or sunset is requested

Returns:

  • (Float) —

    the center equation



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# File 'lib/wrf_library/sun_equation.rb', line 62

def self.calculate_center_equation(date=Time.now, longitude, event)
  m = calculate_solar_mean_anomaly(date, longitude, event)
  rad_m = convert_degree_to_radiant(m)
  l = m + 1.9148 * Math.sin(rad_m) + 0.02 * Math.sin(2*rad_m) + 282.634
  normalize_angle(l)
end

.calculate_current_day_of_year(date = Time.now, longitude, event) ⇒ Float

method to get the day of the year for the given date

Parameters:

  • date (Time) (defaults to: Time.now) —

    the provided date or the current date if none is given

  • longitude (Float) —

    the longitude of the requested location

  • event (Symbol) —

    the information if sunrise or sunset is requested

Returns:

  • (Float) —

    the current day of the day



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# File 'lib/wrf_library/sun_equation.rb', line 43

def self.calculate_current_day_of_year(date=Time.now, longitude, event)
  offset = if (event == :rise) then 6.0 else 18.0 end
  date.yday().to_f + (offset - longitude / @@rotation_time) / 24
end

.calculate_event_time(date = Time.now, longitude, latitude, event) ⇒ Float

method to calculate the time of the given event

Parameters:

  • date (Time) (defaults to: Time.now) —

    the provided date or the current date if none is given

  • longitude (Float) —

    the longitude of the requested location

  • latitude (Float) —

    the latitude of the requested location

  • event (Symbol) —

    the information if sunrise or sunset is requested

Returns:

  • (Float) —

    the hour and minutes as a decimal float of the event



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# File 'lib/wrf_library/sun_equation.rb', line 121

def self.calculate_event_time(date=Time.now, longitude, latitude, event)
  t_l = calculate_local_event_time(date, longitude, latitude, event)
  t_l - longitude / @@rotation_time
end

.calculate_local_event_time(date = Time.now, longitude, latitude, event) ⇒ Float

method to calculate the local time of the given event

Parameters:

  • date (Time) (defaults to: Time.now) —

    the provided date or the current date if none is given

  • longitude (Float) —

    the longitude of the requested location

  • latitude (Float) —

    the latitude of the requested location

  • event (Symbol) —

    the information if sunrise or sunset is requested

Returns:

  • (Float) —

    the hour and minutes as a decimal float of the event



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# File 'lib/wrf_library/sun_equation.rb', line 108

def self.calculate_local_event_time(date=Time.now, longitude, latitude, event)
  h = calculate_local_hour_angle(date, longitude, latitude, event) / 15
  ascension = calculate_sun_ascension(calculate_center_equation(date, longitude, event))
  t = calculate_current_day_of_year(date, longitude, event)
  h + ascension / @@rotation_time - 0.06571* t - 6.622
end

.calculate_local_hour_angle(date = Time.now, longitude, latitude, event) ⇒ Float

method to calculate the local hour angle

Parameters:

  • date (Time) (defaults to: Time.now) —

    the provided date or the current date if none is given

  • longitude (Float) —

    the longitude of the requested location

  • latitude (Float) —

    the latitude of the requested location

  • event (Symbol) —

    the information if sunrise or sunset is requested

Returns:

  • (Float) —

    the local hour angle



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# File 'lib/wrf_library/sun_equation.rb', line 93

def self.calculate_local_hour_angle(date=Time.now, longitude, latitude, event)
  center_equation = calculate_center_equation(date, longitude, event)
  declination = calculate_sun_declination(center_equation)
  cos_h = (@@cos_z - Math.sin(declination) * Math.sin(convert_degree_to_radiant(latitude))) /
          (Math.cos(declination) * Math.cos(convert_degree_to_radiant(latitude)))
  return 360.0 - convert_radiant_to_degree(Math.acos(cos_h)) if (event == :rise)
  convert_radiant_to_degree(Math.acos(cos_h))
end

.calculate_solar_mean_anomaly(date = Time.now, longitude, event) ⇒ Float

method to calculate the solar mean

Parameters:

  • date (Time) (defaults to: Time.now) —

    the provided date or the current date if none is given

  • longitude (Float) —

    the longitude of the requested location

  • event (Symbol) —

    the information if sunrise or sunset is requested

Returns:

  • (Float) —

    the solar mean anomaly



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# File 'lib/wrf_library/sun_equation.rb', line 53

def self.calculate_solar_mean_anomaly(date=Time.now, longitude, event)
  0.98560028 * calculate_current_day_of_year(date, longitude, event) - 3.289
end

.calculate_sun_ascension(center_equation) ⇒ Float

method to calculate the sun ascension value

Parameters:

  • center_equation (Float) —

    the result vaule of the center equation

Returns:

  • (Float) —

    the sun ascension value



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# File 'lib/wrf_library/sun_equation.rb', line 72

def self.calculate_sun_ascension(center_equation)
  ra = Math.atan(0.91746 * Math.tan(convert_degree_to_radiant(center_equation)))
  ran = normalize_angle(convert_radiant_to_degree(ra))
  sun_quadrant = (center_equation / 90.0).floor * 90
  ascension_quadrant = (ran / 90.0).floor * 90
  ran + (sun_quadrant - ascension_quadrant)
end

.calculate_sun_declination(center_equation) ⇒ Float

method to calculate the sun declination value

Parameters:

  • center_equation (Float) —

    the result of the center equation

Returns:

  • (Float) —

    the sun declination value



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# File 'lib/wrf_library/sun_equation.rb', line 83

def self.calculate_sun_declination(center_equation)
  Math.asin(0.39782 * Math.sin(convert_degree_to_radiant(center_equation)))
end

.calculate_sunrise_time(date = Time.now, longitude, latitude) ⇒ Float

method to calculate the time of the sunrise fpr the given data

Parameters:

  • date (Time) (defaults to: Time.now) —

    the provided date or the current date if none is given

  • longitude (Float) —

    the longitude of the requested location

  • latitude (Float) —

    the latitude of the requested location

Returns:

  • (Float) —

    the local timezone hour and minutes as a decimal float of the event



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# File 'lib/wrf_library/sun_equation.rb', line 131

def self.calculate_sunrise_time(date=Time.now, longitude, latitude)
  event_utc = calculate_event_time(date, longitude, latitude, :rise)
  event_utc += 24.0 if (event_utc < 0)
  event_utc -= 24.0 if (event_utc > 24.0)
  event_utc + date.gmt_offset / 3600
end

.calculate_sunset_time(date = Time.now, longitude, latitude) ⇒ Float

method to calculate the time of the sunset fpr the given data

Parameters:

  • date (Time) (defaults to: Time.now) —

    the provided date or the current date if none is given

  • longitude (Float) —

    the longitude of the requested location

  • latitude (Float) —

    the latitude of the requested location

Returns:

  • (Float) —

    the local timezone hour and minutes as a decimal float of the event



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# File 'lib/wrf_library/sun_equation.rb', line 143

def self.calculate_sunset_time(date=Time.now, longitude, latitude)
  event_utc = calculate_event_time(date, longitude, latitude, :sunset)
  event_utc += 24.0 if (event_utc < 0)
  event_utc -= 24.0 if (event_utc > 24.0)
  event_utc + date.gmt_offset / 3600
end

.convert_degree_to_radiant(angle) ⇒ Float

helper method to convert a degree value into radians

Parameters:

  • angle (Float) —

    the angle in degrees

Returns:

  • (Float) —

    the angle in radians



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# File 'lib/wrf_library/sun_equation.rb', line 25

def self.convert_degree_to_radiant(angle)
  angle * Math::PI / 180
end

.convert_radiant_to_degree(angle) ⇒ Float

helper method to convert a radiant value into degrees

Parameters:

  • angle (Float) —

    the angel in radians

Returns:

  • (Float) —

    the angle in degree



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# File 'lib/wrf_library/sun_equation.rb', line 18

def self.convert_radiant_to_degree(angle)
  angle * 180 / Math::PI
end

.normalize_angle(angle) ⇒ Float

helper method to transform the given angle into the interval [-360:360]

Parameters:

  • angle (Float) —

    the given angle

Returns:

  • (Float) —

    the normalized angle



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# File 'lib/wrf_library/sun_equation.rb', line 32

def self.normalize_angle(angle)
  angle -= 360.0 while (angle > 360.0)
  angle += 360.0 while (angle < -360.0)
  angle
end