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

// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

//! Handle (azimuth, elevation) coordinates (also known as horizontal
//! coordinates).

use std::f64::consts::FRAC_PI_2;

use erfa::aliases::eraAe2hd;

use super::hadec::HADec;

/// A struct containing an Azimuth and Elevation. All units are in radians.
#[derive(Clone, Copy, Debug, Default, PartialEq)]
pub struct AzEl {
    /// Hour angle \[radians\]
    pub az: f64,
    /// Declination \[radians\]
    pub el: f64,
}

impl AzEl {
    /// Make a new [`AzEl`] struct from values in radians.
    pub fn from_radians(az_rad: f64, el_rad: f64) -> AzEl {
        Self {
            az: az_rad,
            el: el_rad,
        }
    }

    /// Make a new [`AzEl`] struct from values in degrees.
    pub fn from_degrees(az_deg: f64, el_deg: f64) -> AzEl {
        Self {
            az: az_deg.to_radians(),
            el: el_deg.to_radians(),
        }
    }

    /// Make a new [`AzEl`] struct from values in radians.
    #[deprecated = "use `AzEl::from_radians` instead"]
    pub fn new(az_rad: f64, el_rad: f64) -> AzEl {
        Self {
            az: az_rad,
            el: el_rad,
        }
    }

    /// Make a new [`AzEl`] struct from values in degrees.
    #[deprecated = "use `AzEl::from_degrees` instead"]
    pub fn new_degrees(az_deg: f64, el_deg: f64) -> AzEl {
        Self::from_degrees(az_deg, el_deg)
    }

    /// Get the zenith angle in radians.
    pub fn za(self) -> f64 {
        FRAC_PI_2 - self.el
    }

    /// Convert the horizon coordinates to equatorial coordinates (Hour Angle
    /// and Declination), given the local latitude on Earth.
    pub fn to_hadec(self, latitude_rad: f64) -> HADec {
        let (ha, dec) = eraAe2hd(self.az, self.el, latitude_rad);
        HADec::from_radians(ha, dec)
    }

    /// Convert the horizon coordinates to equatorial coordinates (Hour Angle
    /// and Declination) for the MWA's location.
    pub fn to_hadec_mwa(self) -> HADec {
        self.to_hadec(crate::constants::MWA_LAT_RAD)
    }
}

impl std::fmt::Display for AzEl {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(
            f,
            "({:.4}°, {:.4}°)",
            self.az.to_degrees(),
            self.el.to_degrees()
        )
    }
}

#[cfg(any(test, feature = "approx"))]
impl approx::AbsDiffEq for AzEl {
    type Epsilon = f64;

    fn default_epsilon() -> f64 {
        f64::EPSILON
    }

    fn abs_diff_eq(&self, other: &Self, epsilon: f64) -> bool {
        f64::abs_diff_eq(&self.az, &other.az, epsilon)
            && f64::abs_diff_eq(&self.el, &other.el, epsilon)
    }
}

#[cfg(any(test, feature = "approx"))]
impl approx::RelativeEq for AzEl {
    #[inline]
    fn default_max_relative() -> f64 {
        f64::EPSILON
    }

    #[inline]
    fn relative_eq(&self, other: &Self, epsilon: f64, max_relative: f64) -> bool {
        f64::relative_eq(&self.az, &other.az, epsilon, max_relative)
            && f64::relative_eq(&self.el, &other.el, epsilon, max_relative)
    }

    #[inline]
    fn relative_ne(
        &self,
        other: &Self,
        epsilon: Self::Epsilon,
        max_relative: Self::Epsilon,
    ) -> bool {
        !Self::relative_eq(self, other, epsilon, max_relative)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use approx::assert_abs_diff_eq;

    #[test]
    fn to_hadec() {
        let ae = AzEl::from_degrees(45.0, 30.0);
        let result = ae.to_hadec(-0.497600);
        let expected = HADec::from_radians(-0.6968754873551053, 0.3041176697804004);
        assert_abs_diff_eq!(result, expected, epsilon = 1e-10);
    }

    #[test]
    fn to_hadec2() {
        let ae = AzEl::from_radians(0.261700, 0.785400);
        let result = ae.to_hadec(-0.897600);
        let expected = HADec::from_radians(-0.185499449332533, -0.12732312479328656);
        assert_abs_diff_eq!(result, expected, epsilon = 1e-10);
    }

    #[test]
    fn test_za() {
        let ae = AzEl::from_radians(0.261700, 0.785400);
        let za = ae.za();
        assert_abs_diff_eq!(za, 0.7853963268, epsilon = 1e-10);
    }
}