Create GCS:Xi'an80

       private ISpatialReference GetGCSXian80()
        {
            ISpatialReferenceFactory pSRF = new SpatialReferenceEnvironmentClass();
            //pSRF.CreateProjectedCoordinateSystem(esriSRProjCS4Type.esriSRProjCS_Xian1980_GK_Zone_19);
            //pSRF.CreateGeographicCoordinateSystem((int)esriSRGeoCS3Type.esriSRGeoCS_Xian1980);
            ISpatialReference pSR = pSRF.CreateGeographicCoordinateSystem((int)esriSRGeoCS3Type.esriSRGeoCS_Xian1980);
            return pSR;
        }