转载地址：http://blog.163.com/lai_xiao_hui/blog/static/123037324201151443221942/
代码是将WGS84地理坐标转换为WGS84UTM投影坐标，如果要转换为西安80或北京54坐标，则参数是：
北京54坐标：
地理坐标枚举值为：esriSRGeoCSType.esriSRGeoCS_Beijing1954
投影坐标枚举值为：esriSRProjCSType.esriSRProjCS_Beijing1954GK_13……
西安80坐标：
地理坐标枚举值为：esriSRGeoCS3Type.esriSRGeoCS_Xian1980
投影坐标枚举值为：esriSRProjCS4Type.esriSRProjCS_Xian1980_3_Degree_GK_CM_102E……
public class WGS84UTM
{
/// <summary>
/// 从地理坐标转换到投影坐标
/// </summary>
/// <param name="longitude">经度</param>
/// <param name="latitude">纬度，南半球为负数</param>
/// <param name="x">X</param>
/// <param name="y">Y</param>
/// <param name="zone">带区（1-60，从-180到+180，6度带）</param>
public static void GeoToPrj(double longitude, double latitude, out double x, out double y, out int zone)
{
ISpatialReferenceFactory pSpatialReferenceFactory = new SpatialReferenceEnvironmentClass();
IGeographicCoordinateSystem pGeoCoordSys = pSpatialReferenceFactory.CreateGeographicCoordinateSystem((int)esriSRGeoCSType.esriSRGeoCS_WGS1984);
int startprjnum = 32601;
if (latitude < 0) startprjnum = 32701;
zone = (int)Math.Round(((longitude + 3) / 6)) + 30;
int prjnum = startprjnum + zone - 1;
IProjectedCoordinateSystem pPrjCoordSys = pSpatialReferenceFactory.CreateProjectedCoordinateSystem(prjnum);
IPoint pt = new PointClass();
pt.PutCoords(longitude, latitude);
IGeometry geo = (IGeometry)pt;
geo.SpatialReference = pGeoCoordSys;
geo.Project(pPrjCoordSys);
x = pt.X;
y = pt.Y;
if (latitude < 0)
y = 0 - y;
}
/// <summary>
/// 从投影坐标转换到地理坐标
/// </summary>
/// <param name="x">X</param>
/// <param name="y">Y，南半球为负数</param>
/// <param name="zone">带区（1-60，从-180到+180，6度带）</param>
/// <param name="longitude">经度</param>
/// <param name="latitude">纬度</param>
public static void PrjToGeo(double x, double y, int zone, out double longitude, out double latitude)
{
ISpatialReferenceFactory pSpatialReferenceFactory = new SpatialReferenceEnvironmentClass();
IGeographicCoordinateSystem pGeoCoordSys = pSpatialReferenceFactory.CreateGeographicCoordinateSystem((int)esriSRGeoCSType.esriSRGeoCS_WGS1984);
int startprjnum = 32601;
bool South = false;
if(y < 0)
{
South = true;
y = 0 - y;
}
if (South) startprjnum = 32701;
int prjnum = startprjnum + zone - 1;
IProjectedCoordinateSystem pPrjCoordSys = pSpatialReferenceFactory.CreateProjectedCoordinateSystem(prjnum);
IPoint pt = new PointClass();
pt.PutCoords(x, y);
IGeometry geo = pt as IGeometry;
geo.SpatialReference = pPrjCoordSys;
geo.Project(pGeoCoordSys);
longitude = pt.X;
latitude = pt.Y;
if (South) latitude = 0 - latitude;
}
}