Module: SunTimes
- Defined in:
- lib/sun_times.rb,
lib/sun_times/version.rb
Defined Under Namespace
Modules: VERSION
Constant Summary collapse
- DEFAULT_ZENITH =
90.83333
- KNOWN_EVENTS =
[:rise, :set]
- DEGREES_PER_HOUR =
360.0 / 24.0
Class Method Summary collapse
-
.calculate(event, date, latitude, longitude, options = {}) ⇒ Object
Calculates the sunrise or sunset time for a specific date and location.
-
.rise(date, latitude, longitude, options = {}) ⇒ Object
Helper method: calculates sunrise, with the same parameters as calculate.
-
.set(date, latitude, longitude, options = {}) ⇒ Object
Helper method: calculates sunset, with the same parameters as calculate.
Class Method Details
.calculate(event, date, latitude, longitude, options = {}) ⇒ Object
Calculates the sunrise or sunset time for a specific date and location
Parameters
-
event
- One of :rise, :set. -
date
- An object that responds to :to_datetime. -
latitude
- The latitude of the location in degrees. -
longitude
- The longitude of the location in degrees. -
options
- Additional option is:zenith
.
Example
SunTimes.calculate(:rise, Date.new(2010, 3, 8), 43.779, 11.432)
> Mon Mar 08 05:39:53 UTC 2010
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# File 'lib/sun_times.rb', line 55 def self.calculate(event, date, latitude, longitude, = {}) datetime = date.to_datetime raise "Unknown event '#{ event }'" if KNOWN_EVENTS.find_index(event).nil? zenith = .delete(:zenith) || DEFAULT_ZENITH # lngHour longitude_hour = longitude / DEGREES_PER_HOUR # t base_time = event == :rise ? 6.0 : 18.0 approximate_time = datetime.yday + (base_time - longitude_hour) / 24.0 # M mean_sun_anomaly = (0.9856 * approximate_time) - 3.289 # L sun_true_longitude = mean_sun_anomaly + (1.916 * Math.sin(degrees_to_radians(mean_sun_anomaly))) + (0.020 * Math.sin(2 * degrees_to_radians(mean_sun_anomaly))) + 282.634 sun_true_longitude = coerce_degrees(sun_true_longitude) # RA tan_right_ascension = 0.91764 * Math.tan(degrees_to_radians(sun_true_longitude)) sun_right_ascension = radians_to_degrees(Math.atan(tan_right_ascension)) sun_right_ascension = coerce_degrees(sun_right_ascension) # right ascension value needs to be in the same quadrant as L sun_true_longitude_quadrant = (sun_true_longitude / 90.0).floor * 90.0 sun_right_ascension_quadrant = (sun_right_ascension / 90.0).floor * 90.0 sun_right_ascension += (sun_true_longitude_quadrant - sun_right_ascension_quadrant) # RA = RA / 15 sun_right_ascension_hours = sun_right_ascension / DEGREES_PER_HOUR sin_declination = 0.39782 * Math.sin(degrees_to_radians(sun_true_longitude)) cos_declination = Math.cos(Math.asin(sin_declination)) cos_local_hour_angle = (Math.cos(degrees_to_radians(zenith)) - (sin_declination * Math.sin(degrees_to_radians(latitude)))) / (cos_declination * Math.cos(degrees_to_radians(latitude))) # the sun never rises on this location (on the specified date) return nil if cos_local_hour_angle > 1 # the sun never sets on this location (on the specified date) return nil if cos_local_hour_angle < -1 # H suns_local_hour = if event == :rise 360 - radians_to_degrees(Math.acos(cos_local_hour_angle)) else radians_to_degrees(Math.acos(cos_local_hour_angle)) end # H = H / 15 suns_local_hour_hours = suns_local_hour / DEGREES_PER_HOUR # T = H + RA - (0.06571 * t) - 6.622 local_mean_time = suns_local_hour_hours + sun_right_ascension_hours - (0.06571 * approximate_time) - 6.622 # UT = T - lngHour gmt_hours = local_mean_time - longitude_hour gmt_hours -= 24.0 if gmt_hours > 24 gmt_hours += 24.0 if gmt_hours < 0 offset_hours = datetime.offset * 24.0 if gmt_hours + offset_hours < 0 next_day = datetime.next_day return calculate(event, next_day.new_offset, latitude, longitude, = {}) end if gmt_hours + offset_hours > 24 previous_day = datetime.prev_day return calculate(event, previous_day.new_offset, latitude, longitude, = {}) end hour = gmt_hours.floor hour_remainder = (gmt_hours.to_f - hour.to_f) * 60.0 minute = hour_remainder.floor seconds = (hour_remainder - minute) * 60.0 Time.gm(datetime.year, datetime.month, datetime.day, hour, minute, seconds) end |
.rise(date, latitude, longitude, options = {}) ⇒ Object
Helper method: calculates sunrise, with the same parameters as calculate
34 35 36 |
# File 'lib/sun_times.rb', line 34 def self.rise(date, latitude, longitude, = {}) calculate(:rise, date, latitude, longitude, ) end |
.set(date, latitude, longitude, options = {}) ⇒ Object
Helper method: calculates sunset, with the same parameters as calculate
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# File 'lib/sun_times.rb', line 39 def self.set(date, latitude, longitude, = {}) calculate(:set, date, latitude, longitude, ) end |