public static SqlGeography GeographyToGeography(SqlGeography geog, SqlInt32 toSRID)
{
using (SqlConnection conn = new SqlConnection("context connection=true"))
{
conn.Open();
// Retrieve the parameters of the source spatial reference system
SqlCommand cmd = new SqlCommand("SELECT well_known_text FROM prospatial_reference_systems WHERE spatial_reference_id = @srid", conn);
cmd.Parameters.Add(new SqlParameter("srid", geog.STSrid));
String fromWKT = (String)cmd.ExecuteScalar();
// Create the source coordinate system from WKT
ICoordinateSystem fromCS = ProjNet.Converters.WellKnownText.CoordinateSystemWktReader.Parse(fromWKT) as ICoordinateSystem;
// Retrieve the parameters of the destination spatial reference system
cmd.Parameters["srid"].Value = toSRID;
String toWKT = (String)cmd.ExecuteScalar();
cmd.Dispose();
// Create the destination coordinate system from WKT
ICoordinateSystem toCS = ProjNet.Converters.WellKnownText.CoordinateSystemWktReader.Parse(toWKT) as ICoordinateSystem;
// Create a CoordinateTransformationFactory:
ProjNet.CoordinateSystems.Transformations.CoordinateTransformationFactory ctfac = new ProjNet.CoordinateSystems.Transformations.CoordinateTransformationFactory();
// Create the transformation instance:
ProjNet.CoordinateSystems.Transformations.ICoordinateTransformation trans = ctfac.CreateFromCoordinateSystems(fromCS, toCS);
// create a sink that will create a geometry instance
SqlGeographyBuilder b = new SqlGeographyBuilder();
b.SetSrid((int)toSRID);
// create a sink to do the shift and plug it in to the builder
TransformGeographyToGeographySink s = new TransformGeographyToGeographySink(trans, b);
// plug our sink into the geometry instance and run the pipeline
geog.Populate(s);
// the end of our pipeline is now populated with the shifted geometry instance
return(b.ConstructedGeography);
}
}
protected void ddlProjection_SelectedIndexChanged(object sender, EventArgs e)
{
//Transform current view to new coordinate system and zoom to the transformed box
string PreviousProj = ViewState["currentProj"].ToString();
string SelectedProj = ddlProjection.SelectedValue;
//Points defining the current view
Point left = new Point(myMap.Envelope.MinX, myMap.Center.Y);
Point right = new Point(myMap.Envelope.MaxX, myMap.Center.Y);
Point center = myMap.Center;
if (PreviousProj != "Pseudo")
{
//Transform current view back to geographic coordinates
ProjNet.CoordinateSystems.Transformations.ICoordinateTransformation trans = GetTransform(PreviousProj);
left = GeometryTransform.TransformCoordinate(new Point(myMap.Envelope.MinX, myMap.Center.Y),
trans.MathTransform.Inverse());
right = GeometryTransform.TransformCoordinate(new Point(myMap.Envelope.MaxX, myMap.Center.Y),
trans.MathTransform.Inverse());
center = GeometryTransform.TransformCoordinate(myMap.Center, trans.MathTransform.Inverse());
}
//If both PreviousSRID and SelectedSRID are projected coordsys, first transform to geographic
if (SelectedProj == "Pseudo")
{
myMap.Center = center;
myMap.Zoom = Math.Abs(right.X - left.X);
}
else //Project coordinates to new projection
{
//Transform back to geographic and over to new projection
ProjNet.CoordinateSystems.Transformations.ICoordinateTransformation trans = GetTransform(SelectedProj);
left = GeometryTransform.TransformCoordinate(left, trans.MathTransform);
right = GeometryTransform.TransformCoordinate(right, trans.MathTransform);
center = GeometryTransform.TransformCoordinate(center, trans.MathTransform);
myMap.Center = center;
myMap.Zoom = Math.Abs(right.X - left.X);
var envelopeGcs = GeometryTransform.TransformBox(myMap.Envelope, trans.MathTransform.Inverse());
litEnvelopeLatLong.Text = envelopeGcs.ToString();
}
GenerateMap();
}
