Photos for Mac is assigning an incorrect location

I just converted from iPhotos to Photos (on OS X Sierra). My Photos locations are coming up with names from places far away from where they were taken. Is there some way to make a location on a correction on the entire grouping created by Photos?; I don't want to have to move the pin for each photo. These locations came from the built-in GPS on the device, an iPhone 5 or 4s or Canon camera. How can these be so wrong?