gp执行一直失败，参数改变尝试很多次，但是仍不知道问题出在哪

   //插值分析（克里金法）
       public static void KrigingMethod(IFeatureClass pFeatureClass,string pField,string outResult)
       {
           IFeatureLayer pFeatureLayer = new FeatureLayerClass();
           IDataset pDataset = pFeatureClass as IDataset;
           pFeatureLayer.FeatureClass = pFeatureClass;
           pFeatureLayer.Name = pDataset.Name;

           Geoprocessor gp = new Geoprocessor();
           gp.OverwriteOutput = true;        

           ESRI.ArcGIS.SpatialAnalystTools.Kriging pKiging = new ESRI.ArcGIS.SpatialAnalystTools.Kriging();
           pKiging.in_point_features = pFeatureLayer;
           pKiging.z_field = pField;
           pKiging.semiVariogram_props = "SPHERICAL";
           pKiging.cell_size = "";
           pKiging.out_surface_raster = outResult;
           pKiging.search_radius = "";
           pKiging.out_variance_prediction_raster = "";
           gp.Execute(pKiging, null);                      
       }