marlu 0.16.1

Convenience Rust code that handles coordinate transformations, Jones matrices, I/O. for the Murchison Widefield Array (MWA) radio telescope. Previously known as mwa_rust_core
Documentation 
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// 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);
    }
}