Get UTM coordinate from mouse click in ArcMap using ArcObjects?

Question

I am using ArcObjects C# tool in ArcGIS that identifies map coordinates when a user clicks on a location within a map. Here's the code that I have used:

 protected override void OnMouseDown(MouseEventArgs arg)
 {
 Fr1.Show();
 IMxDocument pMxDoc =(IMxDocument)ArcMap.Application.Document;
 IPoint pPoint = pMxDoc.ActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(arg.X, arg.Y);
 MessageBox.Show("Map X: " + pPoint.X + "\nMap Y: " + pPoint.Y);
 }

My map use units of Meters so the tool displays the Meters coordinates. How can I have this tool return UTM ?

• mkennedy: By UTM, do you mean MGRS or USNG or aother alphanumeric version? For instance, 11SAB23445678 or 11S 345678 4349584?
• Saif Othmani: i mean WGS_1984_UTM_Zone_32N

Answer 1

Once you have your IPoint reference then use the Project method to project it to whatever coordinate system you like.

IGeometry.Project help from Esri

Here's a code example:

Type t = Type.GetTypeFromProgID("esriGeometry.SpatialReferenceEnvironment");
System.Object obj = Activator.CreateInstance(t);
ISpatialReferenceFactory spatialRefFactory= obj as ISpatialReferenceFactory;
ISpatialReference spatialReference = spatialRefFactory.CreateProjectedCoordinateSystem(<ZoneNumber>);
pPoint.Project(spatialReference);

Answer 2

I'm a little confused by your question since UTM is also meters, but the easiest way to change from your current coordinate system to another is to project it.

//get your desired spatial reference
ISpatialReferenceFactory3 spatialReferenceFactory = new SpatialReferenceEnvironment() as ISpatialReferenceFactory3;
ISpatialReference spatialReference = spatialReferenceFactory.CreateSpatialReference((int)esriSRProjCSType.esriSRProjCS_WGS1984UTM_54N); 
pPoint.Project(spatialReference);

In this case it will project to UTM 54N (1984). You can switch that out in the CreateSpatialReference parameter with any of the enumerations in:

• esriSRProjCSType
• esriSRProjCS2Type
• esriSRProjCS3Type
• esriSRProjCS4Type

There are also:

• esriSRGeoCSType

• esriSRGeoCS2Type

• esriSRGeoCS3Type

if you want to go to a geographic coordinate system.

The pPoint.Project() method depends on pPoint already having a SpatialReference assigned to it. I'm not sure if the ToMapPoint() method returns a point with a SpatialReference. If pPoint doesn't have one simply assign it using the

pPoint.SpatialReference = pMxDoc.FocusMap.SpatialReference;