rust_zmanim/util/geolocation.rs
1//! Geolocation struct, with some math for [local mean
2//! time](crate::astronomical_calculator::local_mean_time)
3use crate::util::math_helper::HOUR_MINUTES;
4use jiff::tz::TimeZone;
5
6#[derive(Debug, Clone, PartialEq)]
7/// A struct that contains location information such as latitude and longitude
8/// required for astronomical calculations. The elevation field may be ignored
9/// by calculations that do not account for elevation.
10pub struct GeoLocation {
11 /// The latitude in the World Geodetic System, or degrees North of the
12 /// Equator
13 pub latitude: f64,
14 /// The longitude in the World Geodetic System, or degrees East of the IERS
15 /// Reference Meridian
16 pub longitude: f64,
17 /// The elevation in meters above sea level
18 pub elevation: f64,
19 /// The location's time zone
20 pub timezone: TimeZone,
21}
22impl GeoLocation {
23 /// Returns the location's local mean time offset from UTC in hours. The
24 /// globe is split into 360°, with 15° per hour of the day. For a
25 /// location that is at a longitude evenly divisible by 15 (`longitude
26 /// % 15 == 0`), at solar noon (with adjustment for the equation of time)
27 /// the sun should be directly overhead, so a user who is 1° west of
28 /// this will have noon at 4 minutes after standard time noon, and
29 /// conversely, a user who is 1° east of the 15° longitude will have
30 /// noon at 11:56 AM. Lakewood, N.J., whose longitude is -74.222, is 0.778
31 /// away from the closest multiple of 15 at -75°. This is multiplied by
32 /// 4 to yield 3 minutes and 7 seconds earlier than standard time. The
33 /// offset returned does not account for the daylight saving time offset
34 /// since this struct is unaware of dates.
35 #[must_use]
36 pub fn local_mean_time_offset(&self) -> f64 {
37 (self.longitude * 4.0) / HOUR_MINUTES
38 }
39}