src/base/ossimEllipsoid.cpp

///*******************************************************************
//
// License:  See top level LICENSE.txt file.
//
// DESCRIPTION:
//   Contains implementation of class ossimEllipsoid. The implementation is
//   actually for an OBLATE SPHEROID (x.radius = y.radius) as Earth is
//   considered.
//
// SOFTWARE HISTORY:
//>
//   06Aug2001  Garrett Potts, Oscar Kramer
//              Initial coding.
//<
//*****************************************************************************
//  $Id: ossimEllipsoid.cpp 22858 2014-08-05 17:24:50Z dburken $

#include <ossim/base/ossimEllipsoid.h>
#include <ossim/base/ossimDpt.h>
#include <ossim/base/ossimGpt.h>
#include <ossim/base/ossimEllipsoidFactory.h>
#include <ossim/base/ossimEcefRay.h>
#include <ossim/base/ossimEcefPoint.h>
#include <ossim/base/ossimEcefVector.h>
#include <ossim/base/ossimKeywordNames.h>
#include <ossim/base/ossimKeywordlist.h>
#include <ossim/base/ossimMatrix4x4.h>

//***
// Define Trace flags for use within this file:
//***
#include <ossim/base/ossimTrace.h>
#include <cmath>
static ossimTrace traceExec  ("ossimEllipsoid:exec");
static ossimTrace traceDebug ("ossimEllipsoid:debug");


//*****************************************************************************
//  CONSTRUCTOR: ossimEllipsoid #1 (COPY)
//
//*****************************************************************************
ossimEllipsoid::ossimEllipsoid(const ossimEllipsoid &ellipsoid)
   :
      theName(ellipsoid.theName),
      theCode(ellipsoid.theCode),
      theEpsgCode(ellipsoid.theEpsgCode),
      theA(ellipsoid.theA),
      theB(ellipsoid.theB),
      theFlattening(ellipsoid.theFlattening),
      theA_squared(ellipsoid.theA_squared),
      theB_squared(ellipsoid.theB_squared),
      theEccentricitySquared(ellipsoid.theEccentricitySquared)
{
   if ( theEpsgCode == 0 )
   {
      theEpsgCode = ossimEllipsoidFactory::instance()->findEpsgCode(theCode);
   }
}

//*****************************************************************************
//  CONSTRUCTOR: ossimEllipsoid #2
//
//*****************************************************************************
ossimEllipsoid::ossimEllipsoid(const ossimString &name,
                               const ossimString &code,
                               const double &a,
                               const double &b,
                               ossim_uint32 epsg_code)
   :
      theName(name),
      theCode(code),
      theEpsgCode(epsg_code),
      theA(a),
      theB(b),
      theA_squared(a*a),
      theB_squared(b*b)
{
   if (theEpsgCode == 0)
   {
      theEpsgCode = ossimEllipsoidFactory::instance()->findEpsgCode(theCode);
   }

   computeFlattening();
   theEccentricitySquared = 2*theFlattening - theFlattening*theFlattening;
}

ossimEllipsoid::ossimEllipsoid()
{
   const ossimEllipsoid* ellipse = ossimEllipsoidFactory::instance()->wgs84();

   *this = *ellipse;
}

//*****************************************************************************
//  CONSTRUCTOR: ossimEllipsoid #3
//
//*****************************************************************************
ossimEllipsoid::ossimEllipsoid(const double &a,
                               const double &b)
   :
      theName(""), // initialize to empty
      theCode(""),
      theEpsgCode(0),
      theA(a),
      theB(b),
      theA_squared(a*a),
      theB_squared(b*b)
{
   // First check if this is just WGS84:
   const ossimEllipsoid* wgs84 = ossimEllipsoidFactory::instance()->wgs84();
   if ((theA == wgs84->theA) && (theB == wgs84->theB))
   {
      *this = *wgs84;
   }
   else
   {
      computeFlattening();
      theEccentricitySquared = 2*theFlattening - theFlattening*theFlattening;
   }
}

//*****************************************************************************
//  METHOD: ossimEllipsoid::nearestIntersection
//
//*****************************************************************************
bool ossimEllipsoid::nearestIntersection(const ossimEcefRay &ray,
                                         ossimEcefPoint& rtnPt) const
{
   return nearestIntersection(ray, 0.0, rtnPt);
}

//*****************************************************************************
//  METHOD: ossimEllipsoid::nearestIntersection
//
//   geographic objects that are derive this class will assume that
//   the reference datum is wgs84 and that the ray origin is a
//   geocentric coordinate relative to the wgs84 datum.  Will return
//   true if the object was intersected and false otherwise.
//
//   The nearest intersection will use the ray sphere intersection
//   found in most ray tracers.  We will take a Ray defined by the
//   parametric equation:
//
//     x = x0 + dxt
//     y = y0 + dyt
//     z = z0 + dzt
//
//   and intersect this with the equation of a spheroid:
//
//     x^2/theXRadius^2 + y^2/theYRadius^2 + z^2/theZRadius^2 = 1
//
//   the intersection is achieved by substituting the parametric line
//   into the equation of the spheroid.  By doing this you should
//   get a quadratic in t and the equation should look like this:
//
//    a*t^2 + b*t + c = 0
//
//      let a = dx^2/theXRadius^2 + dy^2/theYRadius^2 + dz^2/theZRadius^2
//      let b = 2*(x0*dx/theXRadius^2 +y0*dy/theYRadius^2 + z0*dz/theZRadius^2
//      let c = x0^2/theXRadius^2 + y0^2/theYRadius^2 + z0^2/theZRadius^2 - 1
//
//    Now solve the quadratic (-b +- sqrt(b^2 - 4ac) ) / 2a
//
//    After solving for t, the parameter is applied to the ray to determine
//    the 3D point position in X,Y,Z, passed back in rtnPt. The boolean
//    "true" is returned if an intersection was found.
//
//    ESH 1/14/2016: I noticed that the radii used for the spheroid are dependent
//    on latitude and this was not taken into account, leading to small errors in
//    the results. The current point on the ray is now used to estimate latitude and
//    update the radii. Iterations stop when the intersection point has an elevation
//    value close to the ellipsoid 'offset'. This approach appears to converge very
//    fast (<=3 iterations). Before this fix, it was noticed that the rtnPt can be
//    off as the absolute value of 'offset' gets large. For example, at 10000 meters,
//    rtnPt can be off by almost 2 centimeters.
//
//*****************************************************************************
bool ossimEllipsoid::nearestIntersection( const ossimEcefRay& ray,
                                          const double&       offset,
                                          ossimEcefPoint&     rtnPt ) const
{
   static const char MODULE[] = "ossimEllipsoid::nearestIntersection";
   if (traceExec())
   {
      ossimNotify(ossimNotifyLevel_DEBUG) << "DEBUG: " << MODULE << ", entering...\n";
   }

   bool success = false;

   const double eccSqComp = 1.0 - theEccentricitySquared;
   const double CONVERGENCE_THRESHOLD = 0.0001;
   const int    MAX_NUM_ITERATIONS    = 10;

   //***
   // get the origin and direction of ray:
   //***
   ossimEcefPoint  start = ray.origin();
   ossimEcefVector direction = ray.direction();

   double start_x = start.x();
   double start_y = start.y();
   double start_z = start.z();

   double direction_x = direction.x();
   double direction_y = direction.y();
   double direction_z = direction.z();

   ossimGpt rayGpt( start );

   int iterations = 0;
   bool done = false;
   do
   {
      double rayLat    = rayGpt.latd();
      double raySinLat = ossim::sind( rayLat );
      double rayScale  = 1.0 / sqrt( 1.0 - theEccentricitySquared * raySinLat * raySinLat );
      double rayN      = theA * rayScale;

      double A_offset = rayN + offset;
      double B_offset = rayN * eccSqComp + offset;

      double A_offset_inv = 1.0 / A_offset;
      double B_offset_inv = 1.0 / B_offset;

      double scaled_x = start_x * A_offset_inv;
      double scaled_y = start_y * A_offset_inv;
      double scaled_z = start_z * B_offset_inv;

      double A_over_B = A_offset * B_offset_inv;

      //***
      // Solve the coefficients of the quadratic formula
      //***

      double a = (direction_x*direction_x + direction_y*direction_y) * A_offset_inv;
      a += (direction_z*direction_z * B_offset_inv * A_over_B);

      double b = 2.0 * ( scaled_x*direction_x + scaled_y*direction_y +
                         scaled_z*direction_z*A_over_B );

      double c = scaled_x*start_x + scaled_y*start_y;
      c += (scaled_z*start_z * A_over_B);
      c -= A_offset;

      //***
      // solve the quadratic
      //***
      double root = b*b - 4.0*a*c;
      if ( root < 0.0 )
      {
         return false;
      }

      double squareRoot = sqrt(root);
      double oneOver2a  = 1.0 / (2.0*a);

      double t1 = (-b + squareRoot) * oneOver2a;
      double t2 = (-b - squareRoot) * oneOver2a;

      //***
      // sort t1 and t2 and take the nearest intersection if they
      // are in front of the ray.
      //***
//      if ( t2 < t1 )
//      {
//         double temp = t1;
//         t1 = t2;
//         t2 = temp;
//      }
//
//      double tEstimate = ( t1 > 0.0 ) ? t1 : t2;

      // OLK: Alternate means to find closest intersection, not necessarily "in front of" origin:
      double tEstimate = t1;
      if (fabs(t2) < fabs(t1))
         tEstimate = t2;

      // Get estimated intersection point.
      ossimEcefPoint rayEcef = ray.extend( tEstimate );

      rayGpt = ossimGpt( rayEcef );
      double offsetError = fabs( rayGpt.height() - offset );
      if ( offsetError < CONVERGENCE_THRESHOLD )
      {
         done = true;
         success = true;
         rtnPt = rayEcef;
      }

   }  while ( (!done) && (iterations++ < MAX_NUM_ITERATIONS) );

   if (iterations >= MAX_NUM_ITERATIONS)
   {
      if(traceDebug())
      {
         ossimNotify(ossimNotifyLevel_WARN)
            << "WARNING ossimEllipsoid::nearestIntersection: Max number of iterations reached"
            << " solving for intersection point. Result is probably inaccurate." << std::endl;
      }
   }

   return success;
}

//*****************************************************************************
//  METHOD: ossimEllipsoid::evaluate(ossimColumnVector3d)
//
//  Returns neg number if inside, 0 if on, and pos number if outside of
//  ellipsoid.
//
//*****************************************************************************
double ossimEllipsoid::evaluate(const ossimEcefPoint &location)const
{
   //***
   // get the axis
   //***
   return (((location.x() * location.x())/theA_squared) +
           ((location.y() * location.y())/theA_squared) +
           ((location.z() * location.z())/theB_squared) - 1.0);
}

//*****************************************************************************
//  METHOD: ossimEllipsoid::gradient()  version A
//
//  Returns vector normal to the ellipsoid at point specified.
//
//*****************************************************************************
void ossimEllipsoid::gradient(const ossimEcefPoint& location,
                              ossimEcefVector&      result) const
{
   result.x() = (2.0*location.x())/theA_squared;
   result.y() = (2.0*location.y())/theA_squared;
   result.z() = (2.0*location.z())/theB_squared;
}

//*****************************************************************************
//  METHOD: ossimEllipsoid::gradient()  version B
//
//  Returns vector normal to the ellipsoid at point specified.
//
//*****************************************************************************
ossimEcefVector
ossimEllipsoid::gradient(const ossimEcefPoint &location)const
{
   ossimEcefVector result;
   gradient(location, result);
   return result;
}


bool ossimEllipsoid::loadState(const ossimKeywordlist& kwl,
                               const char* prefix)
{
   const char* lookup = kwl.find(prefix, ossimKeywordNames::ELLIPSE_CODE_KW);
   bool foundCode = false;
   if(lookup)
   {
      const ossimEllipsoid* ellipse = ossimEllipsoidFactory::instance()->create(ossimString(lookup));

      if(ellipse)
      {
         foundCode = true;
         *this = *ellipse;
      }
   }

   lookup = kwl.find(prefix, ossimKeywordNames::ELLIPSE_EPSG_CODE_KW);
   if (lookup)
   {
      theEpsgCode = ossimString(lookup).toUInt32();
   }

   if(!foundCode)
   {
      const char* majorAxis = kwl.find(prefix,
                                       ossimKeywordNames::MAJOR_AXIS_KW);
      const char* minorAxis = kwl.find(prefix,
                                       ossimKeywordNames::MAJOR_AXIS_KW);

      theName = "";
      theCode = "";
      if(majorAxis && minorAxis)
      {
         theA = ossimString(majorAxis).toDouble();
         theB = ossimString(minorAxis).toDouble();

         computeFlattening();
         theA_squared = theA*theA;
         theB_squared = theB*theB;
      }
      else
      {
         const ossimEllipsoid* ellipse = ossimEllipsoidFactory::instance()->wgs84();

         *this = *ellipse;
      }
   }

   return true;
}

bool ossimEllipsoid::saveState(ossimKeywordlist& kwl,
                               const char* prefix)const
{
   if(theCode != "")
   {
      kwl.add(prefix,
              ossimKeywordNames::ELLIPSE_CODE_KW,
              theCode.c_str(),
              true);

      kwl.add(prefix,
              ossimKeywordNames::ELLIPSE_NAME_KW,
              theName.c_str(),
              true);
   }
   if (theEpsgCode)
   {
      kwl.add(prefix, ossimKeywordNames::ELLIPSE_EPSG_CODE_KW, theEpsgCode, true);
   }

   kwl.add(prefix,
           ossimKeywordNames::MAJOR_AXIS_KW,
           theA,
           true);

   kwl.add(prefix,
           ossimKeywordNames::MINOR_AXIS_KW,
           theB,
           true);

   return true;
}


//*****************************************************************************
//  METHOD: ossimEllipsoid::prinRadiiOfCurv()
//
//  Computes the meridional radius and prime vertical at given point.
//
//*****************************************************************************
void ossimEllipsoid::prinRadiiOfCurv(const ossimEcefPoint& location,
                                           double& merRadius,
                                           double& primeVert) const
{
   double lat, lon, hgt;
   XYZToLatLonHeight(location.x(), location.y(), location.z(), lat, lon, hgt);

   double sinPhi = sin(lat*RAD_PER_DEG);
   double phiFac = 1.0 - theEccentricitySquared*sinPhi*sinPhi;
   primeVert = theA / sqrt(phiFac);
   merRadius = theA*(1.0-theEccentricitySquared) / sqrt(phiFac*phiFac*phiFac);
}


//*****************************************************************************
//  METHOD: ossimEllipsoid::jacobianWrtEcef()
//
//  Forms Jacobian of partials of geodetic WRT ECF at given point.
//           -                           -
//           | pLat/pX  pLat/pY  pLat/pZ |
//    jMat = | pLon/pX  pLon/pY  pLon/pZ |
//           | pHgt/pX  pHgt/pY  pHgt/pZ |
//           -                           -
//
//*****************************************************************************
void ossimEllipsoid::jacobianWrtEcef(const ossimEcefPoint& location,
                                           NEWMAT::Matrix& jMat) const
{
   double primeVert;
   double merRadius;
   double lat, lon, hgt;

   XYZToLatLonHeight(location.x(), location.y(), location.z(), lat, lon, hgt);
   prinRadiiOfCurv(location, merRadius, primeVert);

   double sinPhi = sin(lat*RAD_PER_DEG);
   double cosPhi = cos(lat*RAD_PER_DEG);
   double sinLam = sin(lon*RAD_PER_DEG);
   double cosLam = cos(lon*RAD_PER_DEG);
   double N_plus_h = primeVert + hgt;
   double M_plus_h = merRadius + hgt;

   jMat(1,1) = -sinPhi * cosLam / M_plus_h;
   jMat(2,1) = -sinLam / (cosPhi * N_plus_h);
   jMat(3,1) = cosPhi * cosLam;
   jMat(1,2) = -sinPhi * sinLam / M_plus_h;
   jMat(2,2) =  cosLam / (cosPhi * N_plus_h);
   jMat(3,2) = cosPhi * sinLam;
   jMat(1,3) = cosPhi / M_plus_h;
   jMat(2,3) = 0.0;
   jMat(3,3) = sinPhi;
}


//*****************************************************************************
//  METHOD: ossimEllipsoid::jacobianWrtGeo()
//
//  Forms Jacobian of partials of ECF WRT geodetic at given point.
//           -                           -
//           | pX/pLat  pX/pLon  pX/pHgt |
//    jMat = | pY/pLat  pY/pLon  pY/pHgt |
//           | pZ/pLat  pZ/pLon  pZ/pHgt |
//           -                           -
//
//*****************************************************************************
void ossimEllipsoid::jacobianWrtGeo(const ossimEcefPoint& location,
                                          NEWMAT::Matrix& jMat) const
{
   double primeVert;
   double merRadius;
   double lat, lon, hgt;

   XYZToLatLonHeight(location.x(), location.y(), location.z(), lat, lon, hgt);
   prinRadiiOfCurv(location, merRadius, primeVert);

   double sinPhi = sin(lat*RAD_PER_DEG);
   double cosPhi = cos(lat*RAD_PER_DEG);
   double sinLam = sin(lon*RAD_PER_DEG);
   double cosLam = cos(lon*RAD_PER_DEG);
   double N_plus_h = primeVert + hgt;
   double M_plus_h = merRadius + hgt;

   jMat(1,1) = -M_plus_h * sinPhi * cosLam;
   jMat(2,1) = -M_plus_h * sinPhi * sinLam;
   jMat(3,1) =  M_plus_h * cosPhi;
   jMat(1,2) = -N_plus_h * cosPhi * sinLam;
   jMat(2,2) =  N_plus_h * cosPhi * cosLam;
   jMat(3,2) = 0.0;
   jMat(1,3) = cosPhi * cosLam;
   jMat(2,3) = cosPhi * sinLam;
   jMat(3,3) = sinPhi;
}


//*****************************************************************************
//  METHOD: ossimEllipsoid::geodeticRadius()
//
//  Computes the "geodetic" radius for a given latitude in degrees
//
//*****************************************************************************
double ossimEllipsoid::geodeticRadius(const double& lat) const
{
   double cos_lat = ossim::cosd(lat);
   double sin_lat = ossim::sind(lat);
   double cos2_lat = cos_lat*cos_lat;
   double sin2_lat = sin_lat*sin_lat;
   double a2_cos = theA_squared*cos_lat;
   double b2_sin = theB_squared*sin_lat;

   return sqrt( ( (a2_cos*a2_cos) + (b2_sin*b2_sin) )/ (theA_squared*cos2_lat + theB_squared*sin2_lat));
}

//*************************************************************************************************
//  Computes the "geodetic" radius of curvature of the ellipsoid in the east-west (x) and
//  north-south (y) directions for a given latitude in DEGREES.
//  Taken from http://en.wikipedia.org/wiki/Earth_radius
//*************************************************************************************************
void ossimEllipsoid::geodeticRadii(const double& lat, ossimDpt& radii) const
{
   double cos_lat = ossim::cosd(lat);
   double sin_lat = ossim::sind(lat);
   double cos2_lat = cos_lat*cos_lat;
   double sin2_lat = sin_lat*sin_lat;
   double H = theA_squared*cos2_lat + theB_squared*sin2_lat;
   double H3 = H*H*H;

   radii.x = theA_squared/sqrt(H);
   radii.y = theA_squared*theB_squared/sqrt(H3);
}

void ossimEllipsoid::latLonHeightToXYZ(double lat, double lon, double height,
                                       double &x, double &y, double &z)const
{
    double sin_latitude = ossim::sind(lat);
    double cos_latitude = ossim::cosd(lat);
    double N = theA / sqrt( 1.0 - theEccentricitySquared*sin_latitude*sin_latitude);
    x = (N+height)*cos_latitude*ossim::cosd(lon);
    y = (N+height)*cos_latitude*ossim::sind(lon);
    z = (N*(1-theEccentricitySquared)+height)*sin_latitude;
}

void ossimEllipsoid::XYZToLatLonHeight(double x, double y, double z,
                                       double& lat, double& lon, double& height)const
{

#if 1
  // Author: Norman J. Goldstein (ngoldstein@SystemSolutionsRD.com,
//                              normvcr@telus.net)

  const double tol = 1e-15;
  const double d = sqrt(x*x + y*y);
  const int MAX_ITER = 10;

  const double a2 = theA * theA;
  const double b2 = theB * theB;
  const double pa2 = d * d * a2;
  const double qb2 = z * z * b2;
  const double ae2 = a2 * eccentricitySquared();
  const double ae4 = ae2 * ae2;

  const double c3 = -( ae4/2 + pa2 + qb2 );          // s^2
  const double c4 = ae2*( pa2 - qb2 );               // s^1
  const double c5 = ae4/4 * ( ae4/4 - pa2 - qb2 );   // s^0

  double s0 = 0.5 * (a2 + b2) * hypot( d/theA, z/theB );

  for( int iterIdx = 0; iterIdx < MAX_ITER; ++iterIdx )
  {
    const double pol = c5 + s0 * ( c4 + s0 * ( c3 + s0 * s0 ) );
    const double der = c4 + s0 * ( 2 * c3  + 4 * s0 * s0 );

    const double ds = - pol / der;
    s0 += ds;

    if( fabs( ds ) < tol * s0 )
    {
      const double t = s0 - 0.5 * (a2 + b2);
      const double x_ell = d / ( 1.0 + t/a2 );
      const double y_ell = z / ( 1.0 + t/b2 );

      height = ( d - x_ell ) * x_ell/a2 + ( z - y_ell ) * y_ell/b2;
      height /= hypot( x_ell/a2 ,  y_ell/b2 );

      lat = atan2( y_ell/b2, x_ell/a2 ) * DEG_PER_RAD;
      lon = atan2( y, x ) * DEG_PER_RAD;

      return;
    }
  }

  #else
   double d = sqrt(x*x + y*y);

   double phi2 = z / ((1 - theEccentricitySquared) * d);
   double p = 1.0;
   double phi1 = 0.0;
   double N1 = 0.0;
   double height1 = 0.0;
   int iterIdx = 0;
   const int MAX_ITER = 10;
   if (fabs(phi2) > 1e-16 )
   {
      while ( (p > 1e-17) && (iterIdx < MAX_ITER))
      {
         phi1 = phi2;
         N1 = theA / sqrt(1.0 - (theEccentricitySquared * pow(sin(phi1), 2.0)));
         height1 = (d / cos(phi1) - N1);
         phi2 = atan((z / d) * (1.0 + (theEccentricitySquared * N1 * sin(phi1)) / z));
         p = fabs(phi2 - phi1);
         ++iterIdx;
         /* printf("phi: %e   phi2: %e   p: %e  \n", phi1, phi2, p); */
      }
   }
   else
   {
      phi1 = phi2;
      N1 = theA / sqrt(1.0 - (theEccentricitySquared * pow(sin(phi1), 2.0)));
      height1 = (d / cos(phi1)) - N1;
   }

   /* *Latitude = phi2 * 180/PI; */
   /* *Longitude = atan2(Y, X) * 180/PI; */
   lat = phi2*DEG_PER_RAD;
   lon = atan2(y, x)*DEG_PER_RAD;
   height = height1;
#endif
}

void ossimEllipsoid::computeLocalToWorldTransformFromXYZ(double x, double y, double z,
                                                         ossimMatrix4x4& localToWorld)const
{
   localToWorld = ossimMatrix4x4::createIdentity();
   NEWMAT::Matrix& m = localToWorld.getData();

   // put in the translation
   m[0][3] = x;
   m[1][3] = y;
   m[2][3] = z;


    // normalize X,Y,Z
    double inverse_length = 1.0/sqrt(x*x + y*y + z*z);

    x *= inverse_length;
    y *= inverse_length;
    z *= inverse_length;

    double length_XY = sqrt(x*x + y*y);
    double inverse_length_XY = 1.0/length_XY;

    // Vx = |(-Y,X,0)|
    m[0][0] = -y*inverse_length_XY;
    m[1][0] = x*inverse_length_XY;
    m[2][0] = 0.0;

    // Vy = /(-Z*X/(sqrt(X*X+Y*Y), -Z*Y/(sqrt(X*X+Y*Y),sqrt(X*X+Y*Y))|
    double Vy_x = -z*x*inverse_length_XY;
    double Vy_y = -z*y*inverse_length_XY;
    double Vy_z = length_XY;
    inverse_length = 1.0/sqrt(Vy_x*Vy_x + Vy_y*Vy_y + Vy_z*Vy_z);
    m[0][1] = Vy_x*inverse_length;
    m[1][1] = Vy_y*inverse_length;
    m[2][1] = Vy_z*inverse_length;

    // Vz = (X,Y,Z)
    m[0][2] = x;
    m[1][2] = y;
    m[2][2] = z;

}

ossim_uint32 ossimEllipsoid::getEpsgCode() const
{
   if (!theCode.empty() && (theEpsgCode == 0))
      theEpsgCode = ossimEllipsoidFactory::instance()->findEpsgCode(theCode);
   return theEpsgCode;
}

const ossimEllipsoid& ossimEllipsoid::operator=(const ossimEllipsoid& copy_me)
{
   if (this != &copy_me)
   {
      theName = copy_me.theName;
      theCode = copy_me.theCode;
      theEpsgCode = copy_me.theEpsgCode;
      theA = copy_me.theA;
      theB = copy_me.theB;
      theFlattening = copy_me.theFlattening;
      theA_squared = copy_me.theA_squared;
      theB_squared = copy_me.theB_squared;
      theEccentricitySquared = copy_me.theEccentricitySquared;
   }
   return *this;
}