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Finding the Lat/Long of the centerpoint of current map view.

RogerAsbury

I'm trying to convert some old VB code into C#, and unsure of how to proceed with code that does that task mentioned in the subject. Below is the old vb code. My problem being that I do not know the modern .net sdk equivalents for the calls in C#. It seems like it should be pretty simple to get the view extent and calculate the center, but apparently, it's a bit more involved then I expected. 🙂

Try 'TRY TO GET THE CENTER SCREEN LOCATION FROM THE ACTIVE VIEW, JUST SHOW THE FORM ON ERROR

            Dim pPoint As ESRI.ArcGIS.Geometry.IPoint
            pPoint = New ESRI.ArcGIS.Geometry.Point
            pPoint.X = (m_pArcMapAV.Extent.XMax - m_pArcMapAV.Extent.XMin) / 2 + m_pArcMapAV.Extent.XMin
            pPoint.Y = (m_pArcMapAV.Extent.YMax - m_pArcMapAV.Extent.YMin) / 2 + m_pArcMapAV.Extent.YMin

            Dim pGeoCoordSystem As ESRI.ArcGIS.Geometry.ISpatialReference
            Dim pProjCoordSystem As ESRI.ArcGIS.Geometry.ISpatialReference
            Dim pGeoTrans As ESRI.ArcGIS.Geometry.IGeoTransformation
            Dim pSpatRefFact As ESRI.ArcGIS.Geometry.ISpatialReferenceFactory


            pSpatRefFact = New ESRI.ArcGIS.Geometry.SpatialReferenceEnvironment
            pGeoCoordSystem = pSpatRefFact.CreateGeographicCoordinateSystem(ESRI.ArcGIS.Geometry.esriSRGeoCSType.esriSRGeoCS_WGS1984)
            pProjCoordSystem = pSpatRefFact.CreateProjectedCoordinateSystem(ESRI.ArcGIS.Geometry.esriSRProjCSType.esriSRProjCS_NAD1983SPCS_AK3FT)
            pGeoTrans = pSpatRefFact.CreateGeoTransformation(ESRI.ArcGIS.Geometry.esriSRGeoTransformationType.esriSRGeoTransformation_NAD1983_To_WGS1984_2)

            Dim pGeo As ESRI.ArcGIS.Geometry.IGeometry2
            pGeo = pPoint

            pGeo.SpatialReference = pProjCoordSystem

            pGeo.ProjectEx(pGeoCoordSystem, ESRI.ArcGIS.Geometry.esriTransformDirection.esriTransformForward, pGeoTrans, 0, 0, 0)
            Me.tbxLat.Text = CStr(pPoint.Y)
            Me.tbxLon.Text = CStr(pPoint.X)

        Catch ex As Exception
            'DO NOTHING
        End Try

Also, lol at the code paste feature not having a vb option.

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Accepted answers

GKmieliauskas

I understood that you need the code in VB. The same classes and methods you can call from c#.
8-17 lines in VB code makes projection with transformation. wkid 102633 is code for ArcObjects esriSRProjCS_NAD1983SPCS_AK3FT.

    var areaOfInterest = MapView.Active.Extent;

    MapPoint pPoint = MapPointBuilderEx.CreateMapPoint((areaOfInterest.XMax - areaOfInterest.XMin) / (double)2 + areaOfInterest.XMin, (areaOfInterest.YMax - areaOfInterest.YMin) / (double)2 + areaOfInterest.YMin, MapView.Active.Map.SpatialReference);

    SpatialReference pGeoCoordSystem = SpatialReferenceBuilder.CreateSpatialReference(SpatialReferences.WGS84);

    SpatialReference pProjCoordSystem = SpatialReferenceBuilder.CreateSpatialReference(102633);
    ProjectionTransformation pGeoTrans = ProjectionTransformation.Create(pProjCoordSystem, pGeoCoordSystem);
    MapPoint pProjectedPoint = GeometryEngine.Instance.ProjectEx(pPoint, pGeoTrans) as MapPoint;
    Console.WriteLine(pProjectedPoint.Y);
    Console.WriteLine(pProjectedPoint.X);

Documentation link is here

All comments

GKmieliauskas

Hi,

There is one sample project for VB in Esri Community ArcGIS Pro Samples. Solution is here. Try code below for your functionality:

        Try 'TRY TO GET THE CENTER SCREEN LOCATION FROM THE ACTIVE VIEW, JUST SHOW THE FORM ON ERROR
            Dim areaOfInterest = MapView.Active.Extent

            Dim pPoint As MapPoint
            pPoint = MapPointBuilderEx.CreateMapPoint((areaOfInterest.XMax - areaOfInterest.XMin) / 2 + areaOfInterest.XMin,
                (areaOfInterest.YMax - areaOfInterest.YMin) / 2 + areaOfInterest.YMin, MapView.Active.Map.SpatialReference)

            Dim pGeoCoordSystem As SpatialReference
            Dim pProjCoordSystem As SpatialReference
            Dim pGeoTrans As ProjectionTransformation

            pGeoCoordSystem = SpatialReferenceBuilder.CreateSpatialReference(SpatialReferences.WGS84)
            pProjCoordSystem = SpatialReferenceBuilder.CreateSpatialReference(102633)

            pGeoTrans = ProjectionTransformation.Create(pProjCoordSystem, pGeoCoordSystem)
            Dim pProjectedPoint As MapPoint
            pProjectedPoint = CType(GeometryEngine.Instance.ProjectEx(pPoint, pGeoTrans), MapPoint)
            Console.WriteLine(CStr(pProjectedPoint.Y))
            Console.WriteLine(CStr(pProjectedPoint.X))

        Catch ex As Exception
            'DO NOTHING
        End Try

As I understand your map spatial reference is esriSRProjCS_NAD1983SPCS_AK3FT. So, instead of creating pProjCoordSystem you can use Map spatial reference

RogerAsbury

Here is what I have so far, in C#:

await QueuedTask.Run(() =>
{
    var extent = MapView.Active.Extent;
    MapPoint mapPoint = MapPointBuilder.CreateMapPoint(
        (extent.XMax - extent.XMin) / 2 + extent.XMin,
        (extent.YMax - extent.YMin) / 2 + extent.YMin,
        MapView.Active.Map.SpatialReference
    );

    MessageBox.Show($"Latitude: {mapPoint.Y}\nLongitude: {mapPoint.X}", "Coordinates", MessageBoxButton.OK, MessageBoxImage.Information);
});

For a specific location in Fairbanks, Alaska, this gives me:

However, I would expect something more along the lines of

Latitude: 64.8614161192099

Longitude: -147.90539636224

My guess is that in your vb code, lines 8-17 perform that conversion, but I'm uncertain how to do that in C#. The library names/classes appear to be different? My lack of knowledge on the various spatial reference types is probably not helping.

JonathanDewalt

This would get you the lat / long of your extent.

var extent = rmg.Common.Methods.GetMapViewExtentAsGeometry(this, mapView, null);

// Convert to WGS84
var wgs84 = new SpatialReferenceBuilder(4326).ToSpatialReference();
var projectedCentre = GeometryEngine.Instance.Project(extent, wgs84);

// Get the center of the extent
var center = GeometryEngine.Instance.Centroid(projectedCentre);

dbllat = center?.Y.ToString();
dbllong = center?.X.ToString();

GKmieliauskas

    var areaOfInterest = MapView.Active.Extent;

    MapPoint pPoint = MapPointBuilderEx.CreateMapPoint((areaOfInterest.XMax - areaOfInterest.XMin) / (double)2 + areaOfInterest.XMin, (areaOfInterest.YMax - areaOfInterest.YMin) / (double)2 + areaOfInterest.YMin, MapView.Active.Map.SpatialReference);

    SpatialReference pGeoCoordSystem = SpatialReferenceBuilder.CreateSpatialReference(SpatialReferences.WGS84);

    SpatialReference pProjCoordSystem = SpatialReferenceBuilder.CreateSpatialReference(102633);
    ProjectionTransformation pGeoTrans = ProjectionTransformation.Create(pProjCoordSystem, pGeoCoordSystem);
    MapPoint pProjectedPoint = GeometryEngine.Instance.ProjectEx(pPoint, pGeoTrans) as MapPoint;
    Console.WriteLine(pProjectedPoint.Y);
    Console.WriteLine(pProjectedPoint.X);

Documentation link is here

JonathanDewalt

This would get you the lat / long of your extent in c#

var extent = MapView.Active.Extent;

// Convert to WGS84
var wgs84 = new SpatialReferenceBuilder(4326).ToSpatialReference();
var projectedCentre = GeometryEngine.Instance.Project(extent, wgs84);

// Get the center of the extent
var center = GeometryEngine.Instance.Centroid(projectedCentre);

dbllat = center?.Y.ToString();
dbllong = center?.X.ToString();

RogerAsbury

Thank you both. I tried both solutions and they both work. Love seeing more than one way to arrive at a solution. 🙂 Wish I could mark both as the solution.

Guess I was getting hung up in the conversion.

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