Module: SolarTerms24::Horizons

Defined in:
lib/solar_terms_24/horizons.rb

Overview

:nodoc:

Constant Summary collapse

TIME_FORMAT = 
'%Y-%m-%d %H:%M:%S.%L'
SOLAR_TERMS = 
{
  minor_cold: { month: 1, days: 5..7, longitude: 285 },
  major_cold: { month: 1, days: 19..21, longitude: 300 },
  start_of_spring: { month: 2, days: 3..5, longitude: 315 },
  spring_showers: { month: 2, days: 18..20, longitude: 330 },
  awakening_of_insects: { month: 3, days: 5..7, longitude: 345 },
  spring_equinox: { month: 3, days: 20..22, longitude: 0 },
  pure_brightness: { month: 4, days: 4..6, longitude: 15 },
  grain_rain: { month: 4, days: 19..21, longitude: 30 },
  start_of_summer: { month: 5, days: 5..7, longitude: 45 },
  grain_buds: { month: 5, days: 20..22, longitude: 60 },
  grain_in_ear: { month: 6, days: 5..7, longitude: 75 },
  summer_solstice: { month: 6, days: 20..22, longitude: 90 },
  minor_heat: { month: 7, days: 6..8, longitude: 105 },
  major_heat: { month: 7, days: 22..24, longitude: 120 },
  start_of_autumn: { month: 8, days: 7..9, longitude: 135 },
  end_of_heat: { month: 8, days: 22..24, longitude: 150 },
  white_dew: { month: 9, days: 7..9, longitude: 165 },
  autumn_equinox: { month: 9, days: 22..24, longitude: 180 },
  cold_dew: { month: 10, days: 7..9, longitude: 195 },
  frost: { month: 10, days: 22..24, longitude: 210 },
  start_of_winter: { month: 11, days: 7..9, longitude: 225 },
  minor_snow: { month: 11, days: 21..23, longitude: 240 },
  major_snow: { month: 12, days: 6..8, longitude: 255 },
  winter_solstice: { month: 12, days: 21..23, longitude: 270 }
}.freeze

Class Method Summary collapse

Class Method Details

.fetch_ecliptic_longitudes(start_time, end_time, step:) ⇒ Object 



61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
 
# File 'lib/solar_terms_24/horizons.rb', line 61

def fetch_ecliptic_longitudes(start_time, end_time, step:)
  response = Faraday.get('https://ssd.jpl.nasa.gov/api/horizons.api', {
                           format: 'text',
                           COMMAND: '10',
                           QUANTITIES: '31',
                           START_TIME: "'#{start_time.strftime(TIME_FORMAT)}'",
                           STOP_TIME: "'#{end_time.strftime(TIME_FORMAT)}'",
                           STEP_SIZE: "'#{step}'"
                         })
  lines = response.body.split("\n")
  lines[lines.index('$$SOE') + 1..lines.index('$$EOE') - 1].map do |line|
    # regex matches the time and ecliptic longitude
    matches = line.match(/(\d+-\w+-\d{2} \d{2}:\d{2}|\d+-\w+-\d{2} \d{2}:\d{2}:\d{2}\.\d{3})\s+([\d.]+)/)
    {
      time: matches[1],
      longitude: matches[2].to_f
    }
  end
end

.find_solar_terms_times(year) ⇒ Object 



37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
 
# File 'lib/solar_terms_24/horizons.rb', line 37

def find_solar_terms_times(year)
  whole_year_data = fetch_ecliptic_longitudes(Date.new(year, 1, 5), Date.new(year, 12, 23), step: '1 hour')
  whole_year_data.sort_by! { |d| d[:longitude] }

  SOLAR_TERMS.keys.each_with_object({}) do |key, h|
    range = range_index(whole_year_data, SOLAR_TERMS[key][:longitude])
    range = [whole_year_data[range[0]], whole_year_data[range[1]]]
    # interpolate the time
    longitude_diff = range[1][:longitude] - range[0][:longitude]
    longitude_diff += 360 if longitude_diff.negative?
    target_longitude = SOLAR_TERMS[key][:longitude].zero? ? 360 : SOLAR_TERMS[key][:longitude]
    ratio = (target_longitude - range[0][:longitude]) / longitude_diff
    base_time = DateTime.parse(range[0][:time])
    h[key] = base_time + 1/24r * ratio.to_r
  end
end

.range_index(data, longitude) ⇒ Object 



54
55
56
57
58
59
 
# File 'lib/solar_terms_24/horizons.rb', line 54

def range_index(data, longitude)
  return [data.size - 1, 0] if longitude.zero?

  index = data.bsearch_index { |d| d[:longitude] >= longitude }
  [index - 1, index]
end