You can also use Sync Metadata at the bottom of the right hand panel in Grid. The GPS coordinates is in the Camera Info section.
If you have not used this before it operates on the current selection of images in the Grid. It copies from the "most selected" image to all other images in the selection. You select which metadata fields to be copied in the Synchronize Metadata dialog that pops up. All checked fields will be copied. If one of the checked source field is blank that will erase the data from that field of each of the selected images.