I am trying to follow the instructions here (http://support.esri.com/fr/knowledgebase/techarticles/detail/34585) to align some patch boundaries to the coastline of the UK (buffered by 250m) but it is VERY slow and I can't get it to work right. I suspect this might be because the coastline feature class is in WGS_1984 projection (datum?) and my patch polygons are in OSGB_1936 (British National Grid projection?).
So I've tried using the Project tool to create a copy of the coastline feature class in the same projection as the patches, but it comes out misaligned. I don't understand how it is being projected correctly 'on the fly' but not when I use the project tool!
Hmm... It seems like the two feature classes align properly if I add them both at once to a new empty map, but if I add them one at a time they are misaligned.
It also sounds like the Define Projection was used on one of the files instead of the project tool. I would add each file to a separate data frame and examine their coordinates visually
