marss 0.0.3

Mars celestial simulation crate for the MilkyWay SolarSystem workspace
Documentation 
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pub const MARS_FLATTENING: f64 = 0.005_886_007_56;
pub const MARS_SEMI_MAJOR_M: f64 = crate::MARS_EQUATORIAL_RADIUS;
pub const MARS_SEMI_MINOR_M: f64 = crate::MARS_POLAR_RADIUS;

pub struct LatLon {
    pub lat_deg: f64,
    pub lon_deg: f64,
    pub alt_m: f64,
}

pub struct Cartesian {
    pub x: f64,
    pub y: f64,
    pub z: f64,
}

impl LatLon {
    pub fn new(lat_deg: f64, lon_deg: f64, alt_m: f64) -> Self {
        Self {
            lat_deg,
            lon_deg,
            alt_m,
        }
    }

    pub fn to_cartesian(&self) -> Cartesian {
        let lat = self.lat_deg.to_radians();
        let lon = self.lon_deg.to_radians();
        let a = MARS_SEMI_MAJOR_M;
        let e2 = 2.0 * MARS_FLATTENING - MARS_FLATTENING * MARS_FLATTENING;
        let sin_lat = lat.sin();
        let cos_lat = lat.cos();
        let n = a / (1.0 - e2 * sin_lat * sin_lat).sqrt();
        Cartesian {
            x: (n + self.alt_m) * cos_lat * lon.cos(),
            y: (n + self.alt_m) * cos_lat * lon.sin(),
            z: (n * (1.0 - e2) + self.alt_m) * sin_lat,
        }
    }

    pub fn distance_to(&self, other: &LatLon) -> f64 {
        let r = crate::MARS_RADIUS;
        let d_lat = (other.lat_deg - self.lat_deg).to_radians();
        let d_lon = (other.lon_deg - self.lon_deg).to_radians();
        let lat1 = self.lat_deg.to_radians();
        let lat2 = other.lat_deg.to_radians();
        let a = (d_lat / 2.0).sin().powi(2) + lat1.cos() * lat2.cos() * (d_lon / 2.0).sin().powi(2);
        let c = 2.0 * a.sqrt().asin();
        r * c
    }
}

impl Cartesian {
    pub fn to_latlon(&self) -> LatLon {
        let a = MARS_SEMI_MAJOR_M;
        let e2 = 2.0 * MARS_FLATTENING - MARS_FLATTENING * MARS_FLATTENING;
        let p = (self.x * self.x + self.y * self.y).sqrt();
        let lon = self.y.atan2(self.x).to_degrees();
        let mut lat = (self.z / p).atan();
        for _ in 0..10 {
            let sin_lat = lat.sin();
            let n = a / (1.0 - e2 * sin_lat * sin_lat).sqrt();
            lat = (self.z + e2 * n * sin_lat).atan2(p);
        }
        let sin_lat = lat.sin();
        let n = a / (1.0 - e2 * sin_lat * sin_lat).sqrt();
        let alt = p / lat.cos() - n;
        LatLon {
            lat_deg: lat.to_degrees(),
            lon_deg: lon,
            alt_m: alt,
        }
    }
}