SpherePoint.h

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/*
 * Developed for the LSST Data Management System.
 * This product includes software developed by the LSST Project
 * (https://www.lsst.org).
 * See the COPYRIGHT file at the top-level directory of this distribution
 * for details of code ownership.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
#ifndef LSST_GEOM_SPHEREPOINT_H_
#define LSST_GEOM_SPHEREPOINT_H_
 
#include <cmath>
#include <ostream>
#include <utility>
 
#include "lsst/sphgeom/UnitVector3d.h"
#include "lsst/sphgeom/Vector3d.h"
#include "lsst/geom/Angle.h"
#include "lsst/geom/Point.h"
 
namespace lsst {
namespace geom {

class SpherePoint final {
public:
    SpherePoint(Angle const& longitude, Angle const& latitude);

    SpherePoint(double longitude, double latitude, AngleUnit units);

    explicit SpherePoint(sphgeom::Vector3d const& vector);

    SpherePoint(sphgeom::LonLat const& lonLat) noexcept;

    SpherePoint() noexcept;

    SpherePoint(SpherePoint const& other) noexcept;

    SpherePoint(SpherePoint&& other) noexcept;
 
    ~SpherePoint() noexcept;

    SpherePoint& operator=(SpherePoint const& other) noexcept;

    SpherePoint& operator=(SpherePoint&& other) noexcept;

    operator sphgeom::LonLat() const noexcept;
 
    /*
     * Accessors
     */

    Angle getLongitude() const noexcept { return _longitude * radians; };

    Angle getRa() const noexcept { return _longitude * radians; };

    Angle getLatitude() const noexcept { return _latitude * radians; };

    Angle getDec() const noexcept { return _latitude * radians; };

    Point2D getPosition(AngleUnit unit) const noexcept;

    sphgeom::UnitVector3d getVector() const noexcept;

    Angle operator[](size_t index) const;

    bool atPole() const noexcept {
        // Unit tests indicate we don't need to worry about epsilon-errors, in that
        // Objects constructed from lat=90*degrees, <0,0,1>, etc. all have atPole() = true.
        return fabs(_latitude) >= HALFPI;
    }

    bool isFinite() const noexcept;
 
    /*
     * Comparisons between points
     */

    bool operator==(SpherePoint const& other) const noexcept;

    bool operator!=(SpherePoint const& other) const noexcept;

    std::size_t hash_value() const noexcept;

    Angle bearingTo(SpherePoint const& other) const;

    Angle separation(SpherePoint const& other) const noexcept;
 
    /*
     * Transformations of points
     */

    SpherePoint rotated(SpherePoint const& axis, Angle const& amount) const noexcept;

    SpherePoint offset(Angle const& bearing, Angle const& amount) const;

    std::pair<Angle, Angle> getTangentPlaneOffset(SpherePoint const& other) const;
 
private:
    double _longitude;  // radians
    double _latitude;   // radians

    void _set(sphgeom::UnitVector3d const& unitVector);
};

SpherePoint averageSpherePoint(std::vector<SpherePoint> const& coords);
 
/*
 * Object-level display
 */

std::ostream& operator<<(std::ostream& os, SpherePoint const& point);
 
}  // namespace geom
}  // namespace lsst
 
namespace std {
template <>
struct hash<lsst::geom::SpherePoint> {
    using argument_type = lsst::geom::SpherePoint;
    using result_type = size_t;
    size_t operator()(argument_type const& x) const noexcept { return x.hash_value(); }
};
}  // namespace std
 
#endif /* LSST_GEOM_SPHEREPOINT_H_ */