I have a polygon layer that is not matching the World Street map by a few hundred meters in ArcMap. How can I correct this? I have tried projecting the polygon shapefile to WGS 1984 and WGS_1984_Web_Mercator Auxiliary Sphere but with both, I get: ERROR 000151: The geotransformation is not valid.
You should not need to re-project your shapefile. You can apply a geographic transformation to the Data Frame and the data will 'project-on-the-fly'. If it is still not aligning, the shapefile may have it's coordinate system defined incorrectly. You may then want to clear the coordinate system (delete the .prj file if it's a shapefile) and then try determining what the correct coordinate sytem is.