//
// C++ Interface: viewing_geometry
//
// Description: Compute the position of viewed locations
//
// Author: Nicolas PASCAL, (C) 2012
//
// Copyright: See COPYING file that comes with this distribution
//
// History:
//
//    2012/02/16 : creation
//
//

#ifndef VIEWING_GEOMETRY_H
#define VIEWING_GEOMETRY_H

#include "earth_geometry.h"
#include "geometry.h"

/**
 * @namespace Viewing view point computations
 */
namespace Viewing {
    /**
     * @brief compute the location of a satellite (in Carthesian Geocentric coordinates), using the the observer position (in ECR Geocentric coordinates), the viewing zenith and azimuth angles and the slant range to the observed point
     * Earth is supposed to be a perfect shere having an authalic radius of 6371007.2 m, as specified by the WGS84
     * @param p_v [IN] observer's position in (lat, lon, alt) coordinates, in degrees/meters
     * @param theta_v [IN] zenithal angle in degrees. If observer at earth surface, from normal to line of sight
     * @param phi_v [IN] azimutal angle in degrees. If observer at earth surface, from north to line of sight projection on surface
     * @param slant_range [IN] earth observer to observed satellite distance, in meters
     * @param p_s [OUT] observed point in carthesian Geocentric coordinates, in meters
     */
    void earth_to_sat_from_range (  const Geodetic::Point3D & p_v,
                                    const double & theta_v, const double & phi_v,
                                    const double & slant_range,
                                    Carthesian::Point3D & p_s);
    /**
     * @brief compute the location of a satellite (in Carthesian Geocentric coordinates), using the the observer position (in ECR Geocentric coordinates), the viewing zenith and azimuth angles and the slant range to the observed point
     * Earth is supposed to be a perfect shere having an authalic radius of 6371007.2 m, as specified by the WGS84
     * @param p_v [IN] observer's position in carthesian coordinates in ECR system, in meters
     * @param theta_v [IN] zenithal angle in degrees. If observer at earth surface, from normal to line of sight
     * @param phi_v [IN] azimutal angle in degrees. If observer at earth surface, from north to line of sight projection on surface
     * @param slant_range [IN] earth observer to observed satellite distance, in meters
     * @param p_s [OUT] observed point in carthesian Geocentric coordinates, in meters
     */
    void earth_to_sat_from_range (  const Carthesian::Point3D & p_v,
                                    const double & theta_v, const double & phi_v,
                                    const double & slant_range,
                                    Carthesian::Point3D & p_s);
    /**
     * @brief compute the location of a satellite (in Carthesian Geocentric coordinates), using the the observer position (in ECR Geocentric coordinates), the viewing zenith and azimuth angles and the slant range to the observed point
     * Earth is supposed to be a perfect shere having an authalic radius of 6371007.2 m, as specified by the WGS84
     * @param p_v [IN] observer's position in (lat, lon, alt) coordinates, in degrees/meters
     * @param theta_v [IN] zenithal angle in degrees. If observer at earth surface, from normal to line of sight
     * @param phi_v [IN] azimutal angle in degrees. If observer at earth surface, from north to line of sight projection on surface
     * @param slant_range [IN] earth observer to observed satellite distance, in meters
     * @param p_s [OUT] observed point in carthesian Geocentric coordinates, in meters
     */
    void earth_to_sat_from_range (  const Geodetic::Point3D & p_v,
                                    const double & theta_v, const double & phi_v,
                                    const double & slant_range,
                                    Carthesian::Point3D & p_s);
    /**
     * @brief computes the earth to satellite slant range, when the altitude of the satellite is given
     * Earth is supposed to be a perfect shere having an authalic radius of 6371007.2 m, as specified by the WGS84
     * @param p_v [IN] observer's position in carthesian coordinates in ECR system, in meters
     * @param theta_v [IN] zenithal angle in degrees. If observer at earth surface, from normal to line of sight
     * @param alt_sat [IN] altitude of the satellite above sea mean level, in meters
     * @return earth observer to observed satellite distance, in meters
     */
    double alt_to_range (const Carthesian::Point3D & p_v, const double & theta_v, const double & alt_sat);
    /**
     * @brief computes the earth to satellite slant range, when the altitude of the satellite is given
     * Earth is supposed to be a perfect shere having an authalic radius of 6371007.2 m, as specified by the WGS84
     * @param p_v [IN] observer's position in (lat, lon, alt) coordinates, in degrees/meters
     * @param theta_v [IN] zenithal angle in degrees. If observer at earth surface, from normal to line of sight
     * @param alt_sat [IN] altitude of the satellite above sea mean level, in meters
     * @return earth observer to observed satellite distance, in meters
     */
    double alt_to_range (const Geodetic::Point3D & p_v, const double & theta_v, const double & alt_sat);
    /**
     * @brief compute the location of a satellite (in Carthesian Geocentric coordinates), using the the observer position (in ECR Geocentric coordinates), the viewing zenith and azimuth angles and the satellite altitude above mean sea level
     * Earth is supposed to be a perfect shere having an authalic radius of 6371007.2 m, as specified by the WGS84
     * @param p_v [IN] observer's position in carthesian coordinates in ECR system, in meters
     * @param theta_v [IN] zenithal angle in degrees. If observer at earth surface, from normal to line of sight
     * @param phi_v [IN] azimutal angle in degrees. If observer at earth surface, from north to line of sight projection on surface
     * @param alt_sat [IN] altitude of the satellite above sea mean level, in meters
     * @param p_s [OUT] observed point in carthesian Geocentric coordinates, in meters
     */
    void earth_to_sat_from_alt (  const Carthesian::Point3D & p_v,
                                    const double & theta_v, const double & phi_v,
                                    const double & alt_sat,
                                    Carthesian::Point3D & p_s);
    /**
     * @brief compute the location of a satellite (in Carthesian Geocentric coordinates), using the the observer position (in ECR Geocentric coordinates), the viewing zenith and azimuth angles and the satellite altitude above mean sea level
     * Earth is supposed to be a perfect shere having an authalic radius of 6371007.2 m, as specified by the WGS84
     * @param p_v [IN] observer's position in (lat, lon, alt) coordinates, in meters
     * @param theta_v [IN] zenithal angle in degrees. If observer at earth surface, from normal to line of sight
     * @param phi_v [IN] azimutal angle in degrees. If observer at earth surface, from north to line of sight projection on surface
     * @param alt_sat [IN] altitude of the satellite above sea mean level, in meters
     * @param p_s [OUT] observed point in carthesian Geocentric coordinates, in meters
     */
    void earth_to_sat_from_alt (  const Geodetic::Point3D & p_v,
                                    const double & theta_v, const double & phi_v,
                                    const double & alt_sat,
                                    Carthesian::Point3D & p_s);
}

#endif