Orthographic.cpp

Go to the documentation of this file.

#include "Orthographic.h"

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

#include <QDebug>
#include "Constants.h"
#include "IException.h"
#include "TProjection.h"
#include "Pvl.h"
#include "PvlGroup.h"
#include "PvlKeyword.h"

using namespace std;
namespace Isis {
  Orthographic::Orthographic(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));
      }

      /*
       * Compute and write the default center latitude if allowed and
       * necessary
       */
      if ((allowDefaults) && (!mapGroup.hasKeyword("CenterLatitude"))) {
        double lat = (m_minimumLatitude + m_maximumLatitude) / 2.0;
        mapGroup += PvlKeyword("CenterLatitude", toString(lat));
      }

      // Get the center longitude  & latitude
      m_centerLongitude = mapGroup["CenterLongitude"];
      m_centerLatitude = mapGroup["CenterLatitude"];
      if (IsPlanetocentric()) {
        m_centerLatitude = ToPlanetographic(m_centerLatitude);
      }

      //Restrict center longitude to avoid converting between domains.
      if ((m_centerLongitude < -360.0) || (m_centerLongitude > 360.0)) {
        QString msg = "The center longitude cannot exceed [-360, 360]. "
                      "[" + toString(m_centerLongitude) + "] is not valid";
        throw IException(IException::User, msg, _FILEINFO_);
      }

      // convert to radians, adjust for longitude direction
      m_centerLongitude *= PI / 180.0;
      m_centerLatitude *= PI / 180.0;
      if (m_longitudeDirection == PositiveWest) m_centerLongitude *= -1.0;

      // Calculate sine & cosine of center latitude
      m_sinph0 = sin(m_centerLatitude);
      m_cosph0 = cos(m_centerLatitude);

      /*
       * This projection has a limited lat/lon range (can't do the world)
       * So let's make sure that our lat/lon range is properly restricted!
       * The equation: m_sinph0 * sinphi + m_cosph0 * cosphi * coslon tells us
       * if we are inside of the projection.
       *
       * m_sinph0 = sin(center lat)
       * sinphi = sin(lat)
       * m_cosph0 = cos(center lat)
       * cosphi = cos(lat)
       * coslon = cos(lon - centerLon)
       *
       * Let's apply this equation at the extremes to minimize our lat/lon range
       */
      double sinphi, cosphi, coslon;

      /* Can we project at the minlat, center lon? If not, then we should move
       * up the min lat to be inside the image.
       */
      sinphi = sin(m_minimumLatitude * PI / 180.0);
      cosphi = cos(m_minimumLatitude * PI / 180.0);
      coslon = 1.0; // at lon=centerLon: cos(lon-centerLon) = cos(0) = 1
      if (m_sinph0 * sinphi + m_cosph0 * cosphi * coslon < 1E-10) {
        /*solve for x: a * sin(x) + b * cos(x) * 1 = 0
         *      a * sin(x) + b * cos(x) = 0
         *      a * sin(x) = - b * cos(x)
         *      -(a * sin(x)) / b = cos(x)
         *      -(a / b) = cos(x) / sin(x)
         *      -(b / a) = sin(x) / cos(x)
         *      -(b / a) = tan(x)
         *      arctan(-(b / a)) = x
         *      arctan(-(m_cosph0 / m_sinph0)) = x
         */
        double newMin = atan2(- m_cosph0, m_sinph0) * 180.0 / PI;
        if (newMin > m_minimumLatitude) {
          m_minimumLatitude = newMin;
        } // else something else is off (i.e. longitude range)
      }

      //Restrict the longitude range to 360 degrees to simplify comparisons.
      if ((m_maximumLongitude - m_minimumLongitude) > 360.0) {
        QString msg = "The longitude range cannot exceed 360 degrees.";
        throw IException(IException::User, msg, _FILEINFO_);
      }
    
      sinphi = sin(m_minimumLatitude * PI / 180.0);
      cosphi = cos(m_minimumLatitude * PI / 180.0);

      /* Can we project at the maxlat, center lon? If not, then we should move
       * down the max lat to be inside the image.
       */
      sinphi = sin(m_maximumLatitude * PI / 180.0);
      cosphi = cos(m_maximumLatitude * PI / 180.0);
      coslon = 1.0; // at lon=centerLon: cos(lon-centerLon) = cos(0) = 1
      if (m_sinph0 * sinphi + m_cosph0 * cosphi * coslon < 1E-10) {
        // see above equations for latitude
        double newMax = atan2(- m_cosph0, m_sinph0) * 180.8 / PI;
        if (newMax < m_maximumLatitude && newMax > m_minimumLatitude) {
          m_maximumLatitude = newMax;
        } // else something else is off (i.e. longitude range)
      }
    }
    catch(IException &e) {
      QString message = "Invalid label group [Mapping]";
      throw IException(e, IException::Io, message, _FILEINFO_);
    }
  }

  Orthographic::~Orthographic() {
  }

  bool Orthographic::operator== (const Projection &proj) {
    if (!Projection::operator==(proj)) return false;
    // dont do the below it is a recusive plunge
    Orthographic *ortho = (Orthographic *) &proj;
    if ((ortho->m_centerLongitude != m_centerLongitude) ||
        (ortho->m_centerLatitude != m_centerLatitude)) return false;
    return true;
  }

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

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

   double Orthographic::TrueScaleLatitude() const {
     //Snyder pg. 45
     // no distortion at center of projection (centerLatitude, centerLongitude)
     return m_centerLatitude * 180.0 / PI;// Change to true scale 
   }

  bool Orthographic::SetGround(const double lat, const double lon) {
    // Convert longitude to radians & clean up
    m_longitude = lon;
    double lonRadians = lon * PI / 180.0;
    if (m_longitudeDirection == PositiveWest) lonRadians *= -1.0;

    // Now convert latitude to radians & clean up ... it must be planetographic
    m_latitude = lat;
    double latRadians = lat;
    if (IsPlanetocentric()) latRadians = ToPlanetographic(latRadians);
    latRadians *= PI / 180.0;

    // Compute helper variables
    double deltaLon = (lonRadians - m_centerLongitude);
    double sinphi = sin(latRadians);
    double cosphi = cos(latRadians);
    double coslon = cos(deltaLon);

    // Lat/Lon cannot be projected
    double g =  m_sinph0 * sinphi + m_cosph0 * cosphi * coslon;
    if ((g <= 0.0) && (fabs(g) > 1.0e-10)) {
      m_good = false;
      return m_good;
    }

    // Compute the coordinates
    double x = m_equatorialRadius * cosphi * sin(deltaLon);
    double y = m_equatorialRadius * (m_cosph0 * sinphi - m_sinph0 * cosphi * coslon);

    SetComputedXY(x, y);
    m_good = true;
    return m_good;
  }

  bool Orthographic::SetCoordinate(const double x, const double y) {
    // Save the coordinate
    SetXY(x, y);

    // Declare instance variables and calculate rho
    double rho, con, z, sinz, cosz;
    const double epsilon = 1.0e-10;
    rho = sqrt(GetX() * GetX() + GetY() * GetY());

    /* Error calculating rho - should be less than equatorial radius.
     * 
     * This if statement included "fabs(rho - m_equatorialRadius) < 1E-10 ||"
     * to make the method more stable for limbs but this caused a false failure
     * for some images when rho == m_equatorialRadius.
     */
    if (rho > m_equatorialRadius) {
      m_good = false;
      return m_good;
    }

    // Calculate the latitude and longitude
    m_longitude = m_centerLongitude;
    if (fabs(rho) <= epsilon) {
      m_latitude = m_centerLatitude;
    }
    else {
      con = rho / m_equatorialRadius;
      if (con > 1.0) con = 1.0;
      if (con < -1.0) con = -1.0;
      z = asin(con);
      sinz = sin(z);
      cosz = cos(z);
      con = cosz * m_sinph0 + GetY() * sinz * m_cosph0 / rho;
      if (con > 1.0) con = 1.0;
      if (con < -1.0) con = -1.0;
      m_latitude = asin(con);
      con = fabs(m_centerLatitude) - HALFPI;
      if (fabs(con) <= epsilon) {
        if (m_centerLatitude >= 0.0) {
          m_longitude += atan2(GetX(), -GetY());
        }
        else {
          m_longitude += atan2(GetX(), GetY());
        }
      }
      else {
        con = cosz - m_sinph0 * sin(m_latitude);
        if ((fabs(con) >= epsilon) || (fabs(GetX()) >= epsilon)) {
          m_longitude += atan2(GetX() * sinz * m_cosph0, con * rho);
        }
      }
    }

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

    // Cleanup the longitude
    if (m_longitudeDirection == PositiveWest) m_longitude *= -1.0;
    
    /*
     * When the longitude range is 0 to 360 and the seam is within the 180 displayable degrees,
     * the longitude needs to be converted to its 360 lon domain counterpart. However, if the
     * range is shifted out of the 0 to 360 range, the conversion is not necessary. For example,
     * if the specified range is -180 to 180 and the clon is 0, the lon -90 is valid but will
     * be converted to 270, which does not work with the comparison. The same idea applies if
     * the range is 200 - 500 and the clon is 360. We want to display 270 to 450 (270 - 360 and
     * 0 - 90). However, if 450 is converted to the 360 domain it becomes 90 which is no longer
     * within the original 200 to 500 range.
     */
    // These need to be done for circular type projections
    m_longitude = To360Domain(m_longitude);
    if (m_longitudeDomain == 180) m_longitude = To180Domain(m_longitude);

    // Cleanup the latitude
    if (IsPlanetocentric())
      m_latitude = ToPlanetocentric(m_latitude);
    
    m_good = true;
    return m_good;
  }

  bool Orthographic::XYRange(double &minX, double &maxX, 
                             double &minY, double &maxY) {
    double lat, lon;

    //Restrict lon range to be between -360 and 360
    double adjustedLon;
    double adjustedMinLon = To360Domain(MinimumLongitude());
    double adjustedMaxLon = To360Domain(MaximumLongitude());
    bool correctedMinLon = false;

    if (adjustedMinLon >= adjustedMaxLon) {
      adjustedMinLon -= 360;
      correctedMinLon = true;
    }

    // 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);

    // Walk top and bottom edges
    for (lat = m_minimumLatitude; lat <= m_maximumLatitude; lat += 0.01) {
      lat = lat;
      lon = m_minimumLongitude;
      XYRangeCheck(lat, lon);

      lat = lat;
      lon = m_maximumLongitude;
      XYRangeCheck(lat, lon);
    }

    // Walk left and right edges
    for (lon = m_minimumLongitude; lon <= m_maximumLongitude; lon += 0.01) {
      lat = m_minimumLatitude;
      lon = lon;
      XYRangeCheck(lat, lon);

      lat = m_maximumLatitude;
      lon = lon;
      XYRangeCheck(lat, lon);
    }

    /*
     * Walk the limb.
     * When the pair is valid and within the correct range, reassign min/max x/y.
     *
     *                      , - ~ ~ ~ - ,
     *                  , '               ' ,
     *               ,       _______         ,
     *               ,       |       |         , <----- Walking the limb would not affect an
     *              ,        |       |          ,       image that does not extend to the
     *              ,        |_______|          ,       limits of the projection.
     *              ,   ________________________,_
     *               , |                        , |
     *                ,|                       ,  |
     *                 |,___________________,_'___| <-- This corner would wrap around.
     *                    ' - , _ _ _ ,  '              The image would rotate because the
     *                                                  center lat was closer to the pole.
     *                                                  This would allow for a more completely
     *                                                  longitude range.
     *                           _o__o__
     *                         o|       |o <------------This is the rotated view. If the image
     *                        o |_______| o             limits extend over the pole (due to the
     *                        o     *     o             offset of the center lat) it is possible
     *                         o         o              to have a lon range that is larger than
     *                            o  o                  180 degrees.
     *
     */
    
    for (double angle = 0.0; angle <= 360.0; angle += 0.01) {
      double x = m_equatorialRadius * cos(angle * PI / 180.0);
      double y = m_equatorialRadius * sin(angle * PI / 180.0);

      if (SetCoordinate(x, y)){
        
        adjustedLon =    To360Domain(m_longitude);
        if (adjustedLon > To360Domain(MinimumLongitude()) && correctedMinLon) {
          adjustedLon -= 360;
        }
        if (m_latitude <= m_maximumLatitude &&
            adjustedLon <= adjustedMaxLon &&
            m_latitude >= m_minimumLatitude &&
            adjustedLon >= adjustedMinLon) {
          m_minimumX = qMin(x, m_minimumX);
          m_maximumX = qMax(x, m_maximumX);
          m_minimumY = qMin(y, m_minimumY);
          m_maximumY = qMax(y, m_maximumY);
          XYRangeCheck(m_latitude, adjustedLon);
        }
      }
    }
    // Make sure everything is ordered
    if (m_minimumX >= m_maximumX ||
        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 Orthographic::Mapping() {
    PvlGroup mapping = TProjection::Mapping();

    mapping += m_mappingGrp["CenterLatitude"];
    mapping += m_mappingGrp["CenterLongitude"];

    return mapping;
  }

  PvlGroup Orthographic::MappingLatitudes() {
    PvlGroup mapping = TProjection::MappingLatitudes();
    mapping += m_mappingGrp["CenterLatitude"];

    return mapping;
  }

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

    mapping += m_mappingGrp["CenterLongitude"];

    return mapping;
  }
} // end namespace isis

extern "C" Isis::Projection *OrthographicPlugin(Isis::Pvl &lab,
    bool allowDefaults) {
  return new Isis::Orthographic(lab, allowDefaults);
}