https://community.esri.com/t5/arcgis-pro-questions/are-geographic-transformations-only-for-datum/m-p/1649801#M98863 <P>Hello, my conceptual understanding, along with the ArcGIS Pro Help documentation, is that a <STRONG>geographic transformation</STRONG> is required (for alignment purposes) IF there is a difference between the geographic coordinate system (or underlying geographic coordinate system) of the layer being added to the map and the Map Display. Ok, fine.</P><P>But does this only apply to a difference with the <STRONG>Datum</STRONG>, and its associated <STRONG>Spheroid</STRONG>?<BR /><SPAN>In other words, what about the other major components, like the </SPAN><STRONG>Prime Meridian</STRONG><SPAN> or </SPAN><STRONG>Unit of Measure</STRONG><SPAN>?</SPAN></P><P>I only have data in Greenwich and Degrees, respectively, so I cannot test this out ...I'm just curious because I want to relay this correctly to my students. Thanks.</P> Thu, 11 Sep 2025 17:17:40 GMT Craig_Eissler_Iceman 2025-09-11T17:17:40Z https://community.esri.com/t5/arcgis-pro-questions/are-geographic-transformations-only-for-datum/m-p/1649801#M98863 <P>Hello, my conceptual understanding, along with the ArcGIS Pro Help documentation, is that a <STRONG>geographic transformation</STRONG> is required (for alignment purposes) IF there is a difference between the geographic coordinate system (or underlying geographic coordinate system) of the layer being added to the map and the Map Display. Ok, fine.</P><P>But does this only apply to a difference with the <STRONG>Datum</STRONG>, and its associated <STRONG>Spheroid</STRONG>?<BR /><SPAN>In other words, what about the other major components, like the </SPAN><STRONG>Prime Meridian</STRONG><SPAN> or </SPAN><STRONG>Unit of Measure</STRONG><SPAN>?</SPAN></P><P>I only have data in Greenwich and Degrees, respectively, so I cannot test this out ...I'm just curious because I want to relay this correctly to my students. Thanks.</P> Thu, 11 Sep 2025 17:17:40 GMT https://community.esri.com/t5/arcgis-pro-questions/are-geographic-transformations-only-for-datum/m-p/1649801#M98863 Craig_Eissler_Iceman 2025-09-11T17:17:40Z