How do I modify automatic coordinate transformation in ArcMap?

Discussion created by rlcave on Nov 29, 2010
Latest reply on Dec 3, 2010 by MKennedy-esristaff
When loading layers, ArcMap will automatically transform input coordinates to the coordinate system currently defined on the data frame.  As part of this process, ArcMap may display a dialog that asks the user which datum transformation to use.  We have a requirement to implement an extension that will automate the selection of the datum transformation based on the source and target coordinate systems and the bounds of the data.

To this end, I need a mechanism to get access to the process before ArcMap performs the automatic transformation so that I can modify the IGeoTransformation parameters, but I have not been able to find an event or other way to do this.  I tried hooking up the IActiveViewEvents.ItemAdded event, but that gets fired after the transformation has already taken place.

Is there an event that will allow me to change the IGeoTransformation definition before ArcMap performs its transformation?  If so, a pointer to an example or a code snippet would be greatly appreciated (I will be using C#).