arcobjectsccoordinate system
I have the user select a coordinate system with the Spatial Reference Dialog.
Is there a simple way to determine if the resulting spatial reference is a Projected or Geographic CS?
I would have thought that this would be an attribute of the spatialReference, but it does not seem to be.
Is one layer bigger than your Map Extent?
The following screen shot shows three different Map Controls that have the same layers added to each Map but have dramatically different drawing results because of having different Map.SpatialReference values set. Each Map has its Extent set to approximately to the same geographic area of coverage given the different SpatialReference’s of the layers. The layers being added to each Map Control, in drawing order, are:
ArcGISTiledMapServiceLayer with a SpatialReference WKID = 4326
ArcGISDynamicMapServiceLayer with a SpatialReference WKID = 4269
ArcGISDynamicMapServiceLayer with a SpatialReference WKID = 102113
Map1 displays all three layers without any problem. The ArcGISTiledMapServiceLayer (1) automatically sets the default Map.SpatialReference (WKID = 4326) value and the other layers (2 and 3) have their SpatialReference re-projected on-the-fly by ArcGIS Server.
Map2 only displays layers 2 and 3 (the ArcGISDynamicMapServiceLayer’s) because the Map.SpatialReference (WKID = 4269) has been set manually to something that is different than what the ArcGISTiledMapServiceLayer.SpatialReference is.
Map3 only displays layers 2 and 3 (the ArcGISDynamicMapServiceLayer’s) because the Map.SpatialReference (WKID = 102113) has been set manually to something that is different than what the ArcGISTiledMapServiceLayer.SpatialReference is.
The screen shot matches the code examples provided in this document.
See c# code below. (Updated: refactored)
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using ESRI.ArcGIS.Geometry;
using System.Windows.Forms;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Geodatabase;
using ESRI.ArcGIS.Framework;
namespace HansenAddin
{
public class PickGeoTransButton : ESRI.ArcGIS.Desktop.AddIns.Button
{
public PickGeoTransButton()
{
}
protected override void OnClick()
{
try
{
// let user choose a transformation for projecting from featureclass's spatial ref
// into the dataframe's spatial ref.
var featClass = ((IFeatureLayer)ArcMap.Document.FocusMap.get_Layer(0)).FeatureClass;
var fromSR = ((IGeoDataset)featClass).SpatialReference;
var toSR = ArcMap.Document.FocusMap.SpatialReference;
IGeoTransformation geoTrans;
esriTransformDirection direction;
ChooseGeotrans(fromSR, toSR, ArcMap.Application.hWnd, out geoTrans, out direction);
if (geoTrans != null)
{
MessageBox.Show(String.Format("{0} \n{1} \n{2} \n{3}", geoTrans.Name, fromSR.Name, toSR.Name, direction));
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
public static void ChooseGeotrans(ISpatialReference fromSR, ISpatialReference toSR, int hWnd,
out IGeoTransformation geoTrans, out esriTransformDirection direction)
{
geoTrans = null;
direction = esriTransformDirection.esriTransformForward;
var list = GetTransformations(fromSR, toSR);
if (list.Count == 0)
{
MessageBox.Show(String.Format("No geotransforms to go from {0} to {1}", fromSR.Name, toSR.Name));
return;
}
IListDialog dlg = new ListDialogClass();
foreach (IGeoTransformation gt in list)
dlg.AddString(gt.Name);
if (dlg.DoModal("Choose a Geotransformation", 0, hWnd))
{
geoTrans = list[dlg.Choice];
direction = GetDir(geoTrans, fromSR, toSR);
}
}
public static List<IGeoTransformation> GetTransformations(ISpatialReference fromSR, ISpatialReference toSR)
{
int fromFactcode = GetGCSFactoryCode(fromSR);
int toFactcode = GetGCSFactoryCode(toSR);
var outList = new List<IGeoTransformation>();
// Use activator to instantiate arcobjects singletons ...
var type = Type.GetTypeFromProgID("esriGeometry.SpatialReferenceEnvironment");
var srf = Activator.CreateInstance(type) as ISpatialReferenceFactory2;
var gtSet = srf.CreatePredefinedGeographicTransformations();
gtSet.Reset();
for (int i = 0; i < gtSet.Count; i++)
{
ISpatialReference fromGcsSR;
ISpatialReference toGcsSR;
var geoTrans = (IGeoTransformation)gtSet.Next();
geoTrans.GetSpatialReferences(out fromGcsSR, out toGcsSR);
if ((fromGcsSR.FactoryCode == fromFactcode && toGcsSR.FactoryCode == toFactcode) ||
(fromGcsSR.FactoryCode == toFactcode && toGcsSR.FactoryCode == fromFactcode))
{
outList.Add(geoTrans);
}
}
return outList;
}
private static esriTransformDirection GetDir(IGeoTransformation geoTrans, ISpatialReference sr1, ISpatialReference sr2)
{
int code1 = GetGCSFactoryCode(sr1);
int code2 = GetGCSFactoryCode(sr2);
ISpatialReference fromSR;
ISpatialReference toSR;
geoTrans.GetSpatialReferences(out fromSR, out toSR);
if (fromSR.FactoryCode == code1 && toSR.FactoryCode == code2)
return esriTransformDirection.esriTransformForward;
else if (fromSR.FactoryCode == code2 && toSR.FactoryCode == code1)
return esriTransformDirection.esriTransformReverse;
else
throw new Exception(String.Format("{0} does not support going between {1} and {2}",
geoTrans.Name, sr1.Name, sr2.Name));
}
private static int GetGCSFactoryCode(ISpatialReference sr)
{
if (sr is IProjectedCoordinateSystem)
return ((IProjectedCoordinateSystem)sr).GeographicCoordinateSystem.FactoryCode;
else if (sr is IGeographicCoordinateSystem)
return ((IGeographicCoordinateSystem)sr).FactoryCode;
else
throw new Exception("unsupported spatialref type");
}
protected override void OnUpdate()
{
}
}
}
Best Answer
You can check the object type like so: