Converter from lambert to longitude latitude

geoconverter

// http://gis.stackexchange.com/questions/70089/lambert93-to-wgs84-ign-algorithms-longitude-problem
// http://fr.wikipedia.org/wiki/Projection_conique_conforme_de_Lambert

function GeoConverter() {

   this.M_PI_2         = Math.PI / 2.0;
   this.DEFAULT_EPS    = 0.000001;
   this.E_WGS84        = 0.08181919106;
   this.E2             = this.E_WGS84 / 2.0;
   this.LON_MERID_IERS = 3.0 * Math.PI / 180.0;
   this.N              = 0.7256077650;
   this.C              = 11754255.426;
   this.XS             =    700000.000;
   this.YS             = 12655612.050;

}


GeoConverter.prototype.latitudeFromLatitudeISO = function(latISo) {
      var phi0 = 2 * Math.atan( Math.exp( latISo ) ) - this.M_PI_2;
      var phiI = 2 * atan( pow(( 1 + this.E_WGS84 * sin( phi0 )) / ( 1 - this.E_WGS84 * sin( phi0 )), this.E2) * exp( latISo ) ) - this.M_PI_2;
      var delta = abs( phiI - phi0 );
      while( delta > this.DEFAULT_EPS ){
         phi0 = phiI;
         phiI =
            2 * atan( pow(
                  ( 1 + this.E_WGS84 * sin( phi0 ) ) /
                  ( 1 - this.E_WGS84 * sin( phi0 ) )  , this.E2)
               * exp( latISo ) ) - this.M_PI_2;
         delta = abs( phiI - phi0 );
      }
      return phiI;
}

GeoConverter.prototype.toLatLon = function(x, y) {
      var dX     = x - this.XS;
      var dY     = y - this.YS;
      var R      = Math.sqrt( dX * dX + dY * dY );
      var gamma  = Math.atan( dX / -dY );
      var latIso = -1 / this.N * Math.log( Math.abs( R / this.C ) );
      var lon = Math.toDegrees( this.LON_MERID_IERS + gamma / this.N );
      var lat = Math.toDegrees( latitudeFromLatitudeISO( latIso ));
      return {lon:lon, lat:lat};
}