I am attempting to reshape a heightmap to that of an old scan of a map I have (both pictured below). I would usually reproject the heightmap using GIS software but I have been unable to find the source CRS for the old map so I am attempting to manually reshape it in photoshop.
I have added lines every four degrees in photoshop (as a smart object) and I am hoping that if I can align these two images by getting the lat and lons lined up visually, the underlying the heightmap will match (relatively closely) to the shape of the old map. I've attempted to do this by warping the heightmap but it is really difficult to get them to align this way. There must be some way to get these to match up somewhat closely however.
If there are any other methods for aligning the heightmap to the old map I am all ears.