I have Layer 1, which uses the NAD1983 datum (GCS_North_American_1983). I'm trying to add Layer 2, which uses the 1983-2011 datum (GCS_NAD_1983_2011).

I assume I have to transform the GCS somehow, because I'm given a Geographic Coordinate Systems Warning when I try to add Layer 2.

I've never needed to convert between two NAD datums before. I can't find any resources online about it. Are they fundamentally the same? Or should I accept the very long, complicated default transformation that ArcMap gives me (WGS_1984_(ITRF08)_To_NAD_1983_2011 + WGS_1984_(ITFR00)_To_NAD_1983)?


Your installation of ArcGIS software includes a document called geographic_transformation.pdf. In this document you will find information about which transformation is best for your location. Do not assume the default transformation suggested by the software is the 'best' transformation.

Look here: "C:\Program Files (x86)\ArcGIS\Desktop10.4\Documentation\geographic_transformations.pdf"

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