WGS84 nach Topex Ellipsoid

double a_wgs84 = 6378137.0;
double f_wgs84 = 1 / 298.257223563;
double a_tp = 6378136.3;
double f_tp = 1 / 298.257;										
double r = (a_wgs84 - a_tp + (a_tp * f_tp - a_wgs84 * f_wgs84) * sin(lat_20Hz / 1000000.0)*sin(lat_20Hz / 1000000.0));