solnedgang 0.0.3

Library for calculating the sunrise and sunset times for a specific location on the earth.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251

use chrono::{DateTime, Datelike, Utc};

pub struct SunriseSunsetCalculator {
    /// The latitude for the position for which the time should be calculated for.
    pub latitude: f64,

    /// The longitude for the position for which the time should be calculated for.
    pub longitude: f64,
}

impl SunriseSunsetCalculator {
    fn calc_mean_obliquity_of_ecliptic(&self, t: f64) -> f64 {
        let seconds = 21.448 - t * (46.815_0 + t * (0.000_59 - t * (0.001_813)));
        23.0 + (26.0 + (seconds / 60.0)) / 60.0
    }

    fn calc_geom_mean_long_sun(&self, t: f64) -> f64 {
        //
        let mut l = 280.466_46 + t * (36_000.769_83 + 0.000_303_2 * t);

        //
        loop {
            if l > 360.0 {
                l -= 360.0;
            } else {
                break;
            }
        }

        //
        loop {
            if l < 0.0 {
                l += 360.0;
            } else {
                break;
            }
        }

        //
        l
    }

    fn calc_obliquity_correction(&self, t: f64) -> f64 {
        let e0 = self.calc_mean_obliquity_of_ecliptic(t);
        let omega = 125.04 - 1934.136 * t;
        e0 + 0.002_56 * omega.to_radians().cos()
    }

    fn calc_eccentricity_earth_orbit(&self, t: f64) -> f64 {
        0.016_708_634 - t * (0.000_042_037 + 0.000_000_126_7 * t)
    }

    fn calc_geom_mean_anomaly_sun(&self, t: f64) -> f64 {
        357.529_11 + t * (35_999.050_29 - 0.000_153_7 * t)
    }

    fn calc_equation_of_time(&self, t: f64) -> f64 {
        let epsilon = self.calc_obliquity_correction(t);
        let l0 = self.calc_geom_mean_long_sun(t);
        let e = self.calc_eccentricity_earth_orbit(t);
        let m = self.calc_geom_mean_anomaly_sun(t);
        let mut y = (epsilon.to_radians() / 2.0).tan();

        y *= y;

        let sin2l0 = (2.0 * l0.to_radians()).sin();
        let sinm = m.to_radians().sin();
        let cos2l0 = (2.0 * l0.to_radians()).cos();
        let sin4l0 = (4.0 * l0.to_radians()).sin();
        let sin2m = (2.0 * m.to_radians()).sin();
        let etime = y * sin2l0 - 2.0 * e * sinm + 4.0 * e * y * sinm * cos2l0
            - 0.5 * y * y * sin4l0
            - 1.25 * e * e * sin2m;

        etime.to_degrees() * 4.0 // in minutes of time
    }

    fn calc_time_julian_cent(&self, jd: f64) -> f64 {
        (jd - 2_451_545.0) / 36_525.0
    }

    fn calc_sun_eq_of_center(&self, t: f64) -> f64 {
        let m = self.calc_geom_mean_anomaly_sun(t);
        let mrad = m.to_radians();
        let sinm = mrad.sin();
        let sin2m = (mrad + mrad).sin();
        let sin3m = (mrad + mrad + mrad).sin();

        sinm * (1.914_602 - t * (0.004_817 + 0.000_014 * t))
            + sin2m * (0.019_993 - 0.000_101 * t)
            + sin3m * 0.000_289
    }

    fn calc_sun_true_long(&self, t: f64) -> f64 {
        let l0 = self.calc_geom_mean_long_sun(t);
        let c = self.calc_sun_eq_of_center(t);

        l0 + c // in degrees
    }

    fn calc_sun_apparent_long(&self, t: f64) -> f64 {
        let o = self.calc_sun_true_long(t);
        let omega = 125.04 - 1934.136 * t;
        o - 0.005_69 - 0.004_78 * omega.to_radians().sin() // in degrees
    }

    fn calc_sun_declination(&self, t: f64) -> f64 {
        let e = self.calc_obliquity_correction(t);
        let lambda = self.calc_sun_apparent_long(t);

        let sint = e.to_radians().sin() * lambda.to_radians().sin();
        sint.asin().to_degrees() // in degrees
    }

    fn calc_hour_angle_sunrise(&self, lat: f64, solar_dec: f64) -> f64 {
        let lat_rad = lat.to_radians();
        let sd_rad = solar_dec.to_radians();
        let z: f64 = 90.833;
        (z.to_radians().cos() / (lat_rad.cos() * sd_rad.cos()) - lat_rad.tan() * sd_rad.tan())
            .acos() // in radians
    }

    fn calc_hour_angle_sunset(&self, lat: f64, solar_dec: f64) -> f64 {
        let lat_rad = lat.to_radians();
        let sd_rad = solar_dec.to_radians();
        let z: f64 = 90.833;
        -(z.to_radians().cos() / (lat_rad.cos() * sd_rad.cos()) - lat_rad.tan() * sd_rad.tan())
            .acos() // in radians
    }

    fn calc_jd(&self, year_in: i32, month_in: u32, day: u32) -> f64 {
        let mut year = year_in;
        let mut month = month_in;

        if month <= 2 {
            year -= 1;
            month += 12;
        }

        let a = (f64::from(year) / 100.0).floor();
        let b = 2.0 - a + (a / 4.0).floor();

        (365.25 * (f64::from(year) + 4716.0)).floor()
            + (30.600_1 * (f64::from(month) + 1.0)).floor()
            + f64::from(day)
            + b
            - 1_524.5
    }

    fn calc_jdfrom_julian_cent(&self, t: f64) -> f64 {
        t * 36_525.0 + 2_451_545.0
    }

    /// Calculates the the time for the sunrise in minutes from midnight (UTC).
    ///
    /// # Arguments
    /// * `date` - The date for which the sunrise time should be calculated for.
    pub fn calc_sunrise_utc(&self, date: DateTime<Utc>) -> f64 {
        let julian_date = self.calc_jd(date.year(), date.month(), date.day());
        let t = self.calc_time_julian_cent(julian_date);
        // first pass to approximate sunrise
        let mut eq_time = self.calc_equation_of_time(t);
        let mut solar_dec = self.calc_sun_declination(t);
        let mut hour_angle = self.calc_hour_angle_sunrise(self.latitude, solar_dec);
        let mut delta = self.longitude + hour_angle.to_degrees();
        let mut time_diff = 4.0 * delta; // in minutes of time
        let time_utc = 720.0 - time_diff - eq_time; // in minutes
        let newt = self.calc_time_julian_cent(self.calc_jdfrom_julian_cent(t) + time_utc / 1_440.0);

        eq_time = self.calc_equation_of_time(newt);
        solar_dec = self.calc_sun_declination(newt);

        hour_angle = self.calc_hour_angle_sunrise(self.latitude, solar_dec);
        delta = self.longitude + hour_angle.to_degrees();
        time_diff = 4.0 * delta;

        720.0 - time_diff - eq_time // return time in minutes from midnight
    }

    /// Calculates the the time for the sunset in minutes from midnight (UTC).
    ///
    /// # Arguments
    /// * `date` - The date for which the sunset time should be calculated for.
    pub fn calc_sunset_utc(&self, date: DateTime<Utc>) -> f64 {
        let julian_date = self.calc_jd(date.year(), date.month(), date.day());
        let t = self.calc_time_julian_cent(julian_date);
        // first pass to approximate sunset
        let mut eq_time = self.calc_equation_of_time(t);
        let mut solar_dec = self.calc_sun_declination(t);
        let mut hour_angle = self.calc_hour_angle_sunset(self.latitude, solar_dec);
        let mut delta = self.longitude + hour_angle.to_degrees();
        let mut time_diff = 4.0 * delta; // in minutes of time
        let mut time_utc = 720.0 - time_diff - eq_time; // in minutes
        let newt = self.calc_time_julian_cent(self.calc_jdfrom_julian_cent(t) + time_utc / 1_440.0);

        eq_time = self.calc_equation_of_time(newt);
        solar_dec = self.calc_sun_declination(newt);

        hour_angle = self.calc_hour_angle_sunset(self.latitude, solar_dec);
        delta = self.longitude + hour_angle.to_degrees();
        time_diff = 4.0 * delta;
        time_utc = 720.0 - time_diff - eq_time; // in minutes

        time_utc
        // time_utc + (60 * tzOffset) // return time in minutes from midnight
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use chrono::TimeZone;

    #[test]
    fn calculating_sunrise_in_utc_seconds_works_for_duesseldorf_germany() {
        let calculator = SunriseSunsetCalculator {
            latitude: 51.21875,
            longitude: 6.76341,
        };

        let test_date = Utc.ymd(2019, 10, 4).and_hms(0, 0, 0);

        assert_eq!(
            (calculator.calc_sunrise_utc(test_date) - 337.668) > 0.0,
            true
        );
        assert_eq!(
            (calculator.calc_sunrise_utc(test_date) - 337.668) < 0.0001,
            true
        );
    }

    #[test]
    fn calculating_sunset_in_utc_seconds_works_for_duesseldorf_germany() {
        let calculator = SunriseSunsetCalculator {
            latitude: 51.21875,
            longitude: 6.76341,
        };

        let test_date = Utc.ymd(2019, 10, 4).and_hms(0, 0, 0);

        assert_eq!(
            (calculator.calc_sunset_utc(test_date) - 1024.9458) > 0.0,
            true
        );
        assert_eq!(
            (calculator.calc_sunset_utc(test_date) - 1024.9458) < 0.0001,
            true
        );
    }
}