摘要：
doubley）{IPointpPoint=newPointClass（）；y）；pPoint.Project（pSRF.CreateGeographicCoordinateSystem（（int）esriSRGeoCSType.esrSRGeoCS_Beijing1954））；
jojojojo2002 原文 ArcEngine下投影坐标和经纬度坐标的相互转换
投影转经纬度
private IPoint PRJtoGCS( double x, double y)
{
IPoint pPoint = new PointClass();
pPoint.PutCoords(x, y);
ISpatialReferenceFactory pSRF = new SpatialReferenceEnvironmentClass();
pPoint.SpatialReference = pSRF.CreateProjectedCoordinateSystem( 2414 );
pPoint.Project(pSRF.CreateGeographicCoordinateSystem(( int )esriSRGeoCSType.esriSRGeoCS_Beijing1954));
return pPoint;
}
其中，pPoint.SpatialReference = pSRF.CreateProjectedCoordinateSystem( 2414 );
这行代码是设置pPoint 的空间参考，也就是要转化的点的投影坐标。如果不知道投影坐标的话，转化会报异常。
2414 为该投影的enum 值
pPoint.Project(pSRF.CreateGeographicCoordinateSystem(( int )esriSRGeoCSType.esriSRGeoCS_Beijing1954));
将该点的投影坐标转化为经纬度。
经纬度到投影：
private IPoint GCStoPRJ(IPoint pPoint, int GCSType, int PRJType) { ISpatialReferenceFactory pSRF = new SpatialReferenceEnvironmentClass(); pPoint.SpatialReference = pSRF.CreateGeographicCoordinateSystem(GCSType); pPoint.Project(pSRF.CreateProjectedCoordinateSystem(PRJType)); return pPoint; }