Edge matching in GIMP
Been reading some of the great tutorials on here, and finally getting to work on my own my own project. One particular area I'm struggling with is getting edges of the map to match.
I'm trying to begin with tectonics, so plate boundaries definitely need to cross from the left side of the map to the right. Is there any easy way to get GIMP to treat the surface as a cylinder?
Try applying an Offset to the image layer with the "Wrap around" option selected. If you offset horizontally by half the image's width in pixels, it should correspond to rotating the globe by 180 degrees, so that the map's left and right edges are moved to the center. You can then edit the new center area to get any map features there to align, and then repeat the Offset command to restore the original POV.