IWorkspaceFactory pWSF = new FileGDBWorkspaceFactoryClass();
IFeatureWorkspace pFWS = (IFeatureWorkspace)pWSF.OpenFromFile(@"D:\gis数据\测试0303.gdb", 0);
IFeatureClass Featureclass = pFWS.OpenFeatureClass("CS");
IFeatureClass Featureclass2 = pFWS.OpenFeatureClass("CS_4547");
IFeatureClass Featureclass3 = pFWS.OpenFeatureClass("CS_4548");
IFeatureClass Featureclass4 = pFWS.OpenFeatureClass("CS_4549");
var fcur = Featureclass.Search(null, false);
var fcur2 = Featureclass2.Search(null, false);
var fcur3 = Featureclass3.Search(null, false);
var fcur4 = Featureclass4.Search(null, false);
IFeature pFeature = fcur.NextFeature();
IFeature pFeature2 = fcur2.NextFeature();
IFeature pFeature3 = fcur3.NextFeature();
IFeature pFeature4 = fcur4.NextFeature();
IPolygon polygon = pFeature.ShapeCopy as IPolygon;
IPolygon polygon2 = pFeature2.ShapeCopy as IPolygon;
IPolygon polygon3 = pFeature3.ShapeCopy as IPolygon;
IPolygon polygon4 = pFeature4.ShapeCopy as IPolygon;
IArea pArea = polygon as IArea;
IArea pArea2 = polygon2 as IArea;
IArea pArea3 = polygon3 as IArea;
IArea pArea4 = polygon4 as IArea;
double area = Math.Abs(pArea.Area);
double area2 = Math.Abs(pArea2.Area);
double area3 = Math.Abs(pArea3.Area);
double area4 = Math.Abs(pArea4.Area);
//4490
IAreaGeodetic areaGeodetic = polygon as IAreaGeodetic;
ISpatialReferenceFactory srf = new SpatialReferenceEnvironmentClass();
ILinearUnit unit = srf.CreateUnit((int)esriSRUnitType.esriSRUnit_Meter) as ILinearUnit;
double area11 = areaGeodetic.get_AreaGeodetic(esriGeodeticType.esriGeodeticTypeGeodesic, unit);
//zhaun4547转4490
//IGeometry geo22 = (IGeometry)po
同一个图形作转换与对比：
//总结：4547,4548转换成4490，然后计算其面积跟4490的是相差不多的
//4547转4548或者是转4549，跟没有转换的4548，4549的也是相差不多的
//如果没有转换的话，相同的图斑4490与4547,4548，4549...的面积是依次相差越来越大的