Mollweide.cpp

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#include "Mollweide.h"


#include <cfloat>
#include <cmath>
#include <iomanip>

#include "Constants.h"
#include "IException.h"
#include "TProjection.h"
#include "Pvl.h"
#include "PvlGroup.h"
#include "PvlKeyword.h"

using namespace std;


namespace Isis {


  Mollweide::Mollweide(Pvl &label, bool allowDefaults) :
      TProjection::TProjection(label) {
    try {
      // Try to read the mapping group
      PvlGroup &mapGroup = label.findGroup("Mapping", Pvl::Traverse);

      // Compute and write the default center longitude if allowed and
      // necessary
      if ((allowDefaults) && (!mapGroup.hasKeyword("CenterLongitude"))) {
        double lon = (m_minimumLongitude + m_maximumLongitude) / 2.0;
        mapGroup += PvlKeyword("CenterLongitude", toString(lon));
      }

      // Get the center longitude
      m_centerLongitude = mapGroup["CenterLongitude"];

      // convert to radians, adjust for longitude direction
      m_centerLongitude *= PI / 180.0;
      if (m_longitudeDirection == PositiveWest) m_centerLongitude *= -1.0;
    }
    catch(IException &e) {
      QString message = "Invalid label group [Mapping]";
      throw IException(e, IException::Io, message, _FILEINFO_);
    }
  }

  Mollweide::~Mollweide() {
  }


  bool Mollweide::operator== (const Projection &proj) {
    if (!TProjection::operator==(proj)) return false;
    // dont do the below it is a recursive plunge
    //  if (TProjection::operator!=(proj)) return false;
    Mollweide *moll = (Mollweide *) &proj;
    if (moll->m_centerLongitude != m_centerLongitude) return false;
    return true;
  }


  QString Mollweide::Name() const {
    return "Mollweide";
  }


  QString Mollweide::Version() const {
    return "1.0";
  }


  bool Mollweide::newton_rapheson(double phi, double &result) {
    
    double dtheta = 1.0;
    int niter = 0;
    double theta[2];
  
    theta[0] = asin(2*phi/PI);
    theta[1]=0.0;
    
    //If this condition is too strict, a larger epsilon value than DBL_EPSILON
    //can be used to decrease the number of iterations.
    while (dtheta > DBL_EPSILON) {

      theta[1] = theta[0] - (2*theta[0]+sin(2*theta[0]) -(Isis::PI)*sin(phi))/(2+2*cos(theta[0]));
      dtheta = fabs(theta[1]-theta[0]);
      theta[0] = theta[1];
      niter++;
      
      if (niter > 15000000) {
        //cout << setprecision(10) << phi*(180/PI) << "," << niter << endl;
        return false;
      }
    }
    result = theta[1];


    //cout << setprecision(10) << phi*(180/PI) << "," << niter << endl;
    return true;
  }


  bool Mollweide::SetGround(const double lat, const double lon) {

    // Convert to radians   
    m_latitude = lat;
    m_longitude = lon;
    double theta;
    double latRadians = lat * PI / 180.0;
    double lonRadians = lon * PI / 180.0;
    if (m_longitudeDirection == PositiveWest) lonRadians *= -1.0;

    // Compute the coordinate
    double deltaLon = lonRadians - m_centerLongitude;

    if (newton_rapheson(latRadians,theta) ) {

      double x = (2*sqrt(2)/PI )*m_equatorialRadius*(deltaLon)*cos(theta);   
      double y = sqrt(2)*m_equatorialRadius*sin(theta);
      
      SetComputedXY(x, y);
      m_good = true;
      return m_good;
    }
    else {

      m_good = false;
      return m_good;
    }
  }


  bool Mollweide::SetCoordinate(const double x, const double y) {
    // Save the coordinate
    
    SetXY(x, y);
  
    double theta = asin(y/(m_equatorialRadius*sqrt(2)));

    // Compute latitude and make sure it is not above 90
    m_latitude = asin((2*theta+sin(2*theta))/(Isis::PI));

    if (fabs(m_latitude) > HALFPI) {
      if (fabs(HALFPI - fabs(m_latitude)) > DBL_EPSILON) {
        m_good = false;
        return m_good;
      }
      else if (m_latitude < 0.0) {
        m_latitude = -HALFPI;
      }
      else {
        m_latitude = HALFPI;
      }
    }

    // Compute longitude

    double cosLat = cos(m_latitude);

    if (cosLat <= DBL_EPSILON) {
      m_longitude = m_centerLongitude;
    }

    else {
    m_longitude = m_centerLongitude+(Isis::PI)*GetX()/(2*m_equatorialRadius*sqrt(2)*cos(theta));
    }


    // Convert to degrees
    m_latitude *= 180.0 / PI;
    m_longitude *= 180.0 / PI;

    // Cleanup the longitude
    if (m_longitudeDirection == PositiveWest) m_longitude *= -1.0;


    // Our double precision is not good once we pass a certain magnitude of
    //   longitude. Prevent failures down the road by failing now.
    m_good = (fabs(m_longitude) < 1E10);


    return m_good;
  }


  bool Mollweide::XYRange(double &minX, double &maxX,
                           double &minY, double &maxY) {
    // Check the corners of the lat/lon range
    XYRangeCheck(m_minimumLatitude, m_minimumLongitude);
    XYRangeCheck(m_maximumLatitude, m_minimumLongitude);
    XYRangeCheck(m_minimumLatitude, m_maximumLongitude);
    XYRangeCheck(m_maximumLatitude, m_maximumLongitude);

    // If the latitude crosses the equator check there
    if ((m_minimumLatitude < 0.0) && (m_maximumLatitude > 0.0)) {
      XYRangeCheck(0.0, m_minimumLongitude);
      XYRangeCheck(0.0, m_maximumLongitude);
    }

    // Make sure everything is ordered
    if (m_minimumX >= m_maximumX) return false;
    if (m_minimumY >= m_maximumY) return false;

    // Return X/Y min/maxs
    minX = m_minimumX;
    maxX = m_maximumX;
    minY = m_minimumY;
    maxY = m_maximumY;
    return true;
  }


  PvlGroup Mollweide::Mapping()  {
    PvlGroup mapping = TProjection::Mapping();

    mapping += m_mappingGrp["CenterLongitude"];

    return mapping;
  }


  PvlGroup Mollweide::MappingLatitudes() {
    PvlGroup mapping = TProjection::MappingLatitudes();

    return mapping;
  }


  PvlGroup Mollweide::MappingLongitudes() {
    PvlGroup mapping = TProjection::MappingLongitudes();

    mapping += m_mappingGrp["CenterLongitude"];

    return mapping;
  }

} // end namespace isis


extern "C" Isis::TProjection *MollweidePlugin(Isis::Pvl &lab,
    bool allowDefaults) {
  return new Isis::Mollweide(lab, allowDefaults);
}